U.S. Department of the Interior

U.S. Geological Survey

Pamphlet to accompany

Scientific Investigations Map 3303

Geology and Hydrostratigraphy of Guadalupe River State 

Park and Honey Creek State Natural Area, Kendall and 

Comal Counties, Texas
COVER. North bank of Honey Creek looking downstream to the confluence with the Guadalupe 

River. Photo taken by Allan Clark, U.S. Geological Survey. 
Geology and Hydrostratigraphy of 

Guadalupe River State Park and Honey 

Creek State Natural Area, Kendall and 

Comal Counties, Texas

By Allan K. Clark, Charles D. Blome, and Robert R. Morris

Pamphlet to accompany

Scientific Investigations Map 3303

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2014

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Suggested citation:

Clark, A.K., Blome, C.D., and Morris, R.R., 2014, Geology and hydrostratigraphy of Guadalupe River State Park and 

Honey Creek State Natural Area, Kendall and Comal Counties, Texas: U.S. Geological Survey Scientific Investigations 

Map 3303, 8 p., 1 sheet, scale 1:24,000, http://dx.doi.org/10.3133/sim3303.

ISSN 2329-132X (online)
iii

Sheet

1. Geology and Hydrostratigraphy of Guadalupe River State Park and Honey Creek 

State Natural Area, Kendall and Comal Counties, Texas ................................................... link

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................2

Description of the Study Area ............................................................................................................2

Methods of Investigation ....................................................................................................................3

Geologic Framework .....................................................................................................................................3

Lithostratigraphy...................................................................................................................................3

Hydrostratigraphy.................................................................................................................................4

Structural Features...............................................................................................................................5

Summary..........................................................................................................................................................6

Acknowledgments.........................................................................................................................................6

References Cited............................................................................................................................................6
iv

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Flow rate

cubic foot per second (ft3

/s) 0.02832 cubic meter per second (m3/s)

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.
Abstract

Hydrogeologic mapping and descriptions of the 

lithostratigraphy and hydrostratigraphy of Guadalupe River 

State Park and Honey Creek State Natural Area, Kendall and 

Comal Counties, Texas, are presented in this first detailed 

1:24,000 geologic map, along with proposed names and 

descriptions of the hydrostratigraphic units in the study area. 

Variations in the amount and type of porosity of the lithostratigraphic unit, which vary depending on the depositional environment, lithology, structural history and diagenesis support 

the resulting hydrostratigraphy proposed herein. 

Rocks exposed in the study area consist of Early 

Cretaceous sedimentary rocks that are assigned to the 

Trinity Group. The lithostratigraphy includes the Hammett 

Shale, Cow Creek Limestone, Hensell Sand Members of the 

Pearsall Formation, and the lower member of the Glen Rose 

Limestone. These lithologic units contain shale, grainstone, 

sandstone, and fossiliferous limestone, alternating and interfingering with mudstone, wackestone, packstone, and grainstone. 

The Trinity aquifer hydrostratigraphic units shown on the 

map and described herein are characterized by their porosity 

types. Porosity types were first determined from an analysis of 

two boreholes conducted in comparison with 143 geophysical

logs from northern Bexar County, Texas. The cores and 

geophysical log comparison resulted in division of the lower 

member of the Glen Rose Limestone into six hydrostratigraphic units, designated A through F. Of those six units, only 

three remain in the study area because of erosion. The proposed naming of these three hydrostratigraphic units is based 

on topographic or historical features that occur in the outcrop 

area of those units. Hydrostratigraphic units that correlate with 

the boundaries of the formation have been given formational 

names excluding the lithologic modifier. The Doeppenschmidt 

hydrostratigraphic unit is stratigraphically the highest interval in the study area, characterized by interparticle, moldic, 

burrowed, bedding plane, fracture, and cave porosity. The 

underlying Rust hydrostratigraphic unit appears to be a confining unit with springs/seeps issuing near the contact with the 

overlying Doeppenschmidt unit. The Rust unit has interparticle, fracture, and cave porosity with cave porosity primarily 

associated with faulting. The Honey Creek hydrostratigraphic 

unit is an aquifer in the subsurface and exhibits extremely, 

well developed porosity and permeability including— 

interparticle, moldic, burrowed, bedding plane, fracture, 

channel, and cave porosity. This unit is named for Honey 

Creek Cave, which discharges water into Honey Creek. The 

Hensell hydrostratigraphic unit contains primarily interparticle 

porosity, but also exhibits some moldic and cave porosity in its 

upper parts. The Cow Creek hydrostratigraphic unit contains 

interparticle, moldic, vug, burrowed, fracture, bedding plane, 

channel, and cave porosity. The Cow Creek hydrostratigraphic 

unit is an aquifer in the subsurface and is the primary target 

for water-well drillers in the area. The Hammett hydrostratigraphic unit is not exposed in the study area but is thought to 

underlie parts of the Guadalupe River, based on mapping of 

the overlying units and comparisons with subsurface thicknesses obtained from the geophysical log. The Hammett unit 

restricts the downward migration of groundwater, resulting in 

springs that discharge at the base of the Cow Creek unit. These 

springs also create some base flow to the Guadalupe River 

during periods of extreme drought. 

The faulting and fracturing in the study area are part of 

the Miocene Balcones Fault Zone, which is an extensional 

system of faults that generally trend southwest to northeast 

in south-central Texas. An igneous dike, containing aphanitic 

texture, cuts through the center of the study area near the 

confluence of Honey Creek and the Guadalupe River. The dike 

penetrates the Cow Creek Limestone and the lower part of the 

Hensell Sand, which outcrops at three locations.

Introduction

The study area is located in Guadalupe River State Park 

(GRSP) and the adjoining Honey Creek State Natural Area 

(HCSNA) in Kendall and Comal Counties, Texas (fig. 1), and 

is underlain by the Early Cretaceous Trinity Group. The GRSP 

Geology and Hydrostratigraphy of Guadalupe River 

State Park and Honey Creek State Natural Area, 

Kendall and Comal Counties, Texas

By Allan K. Clark, Charles D. Blome, and Robert R. Morris
2 Geology and Hydrostratigraphy of Guadalupe River State Park and Honey Creek State Natural Area, TX

is developed and provides camping sites for both recreational 

vehicles and tents, parking areas and restrooms for day-use 

visitors, picnic areas, river access points, and hiking trails. The 

adjacent HCSNA is undeveloped, with the exception of a few 

historic roads and buildings that are accessible by guided tours 

only. Both GRSP and HCSNA are administered by the Texas 

Parks and Wildlife Department (TPWD).

The Early Cretaceous Trinity Group consists of limestone, 

sand, clay, gravel, and conglomerate (George and others, 2011) 

that compose the Hosston Formation (Imlay, 1940), Sligo 

Formation (Warner and Moody, 1992), Pearsall Formation 

(Imlay, 1940), and the Glen Rose Limestone (Hill, 1891). The 

Pearsall Formation has been further subdivided into the Hammett Shale (Lozo and Stricklin, 1956), Cow Creek Limestone 

(Barnes, 1976), and Hensell Sand (Barnes, 1976), and the Glen 

Rose Limestone has been subdivided into a lower and upper 

member (Hill, 1891; Whitney, 1952).These rocks compose 

the entire Trinity aquifer, which is subdivided into the upper, 

middle, and lower Trinity aquifers (Ashworth, 1983).

According to Ashworth (1983), the upper Trinity aquifer 

is contained in the upper member of the Glen Rose Limestone, the middle Trinity aquifer is formed by the Cow Creek 

Limestone, Hensell Sand, and the lower member of the Glen 

Rose Limestone, and the lower Trinity aquifer is formed in 

the Hosston and Sligo Formations. The Hammett Shale is a 

confining unit between the lower and middle Trinity aquifers 

(Ashworth, 1983). However, in the study area, only the 

Hammett Shale, the Cow Creek Limestone, Hensell Sand, and 

part of the lower member of the Glen Rose Limestone, which 

compose the lower 80% of the Middle Trinity aquifer, are 

exposed at the surface.

Although the Trinity aquifer is classified as a major 

aquifer by the State of Texas, transmissivities and water yields 

can be comparatively lower than other aquifers in the area 

(Mace and others, 2000, and Maclay, 1995) resulting in other 

available sources of water being used. New development and 

increased drought conditions have combined to renew interest 

in the Trinity aquifer and concerns about groundwater availability (Mace and others, 2000).

The Trinity aquifer is a karst system formed from the 

dissolution of carbonate rocks by water. Distinctive landforms 

are created from the dissolution with numerous springs and 

karst features—caves, sinkholes, and other visible areas of 

solution-enlarged porosity. Karst features can have an appreciable effect on the hydrologic characteristics of an area because 

they can act as points of focused recharge (Hanson and Small, 

1995; U.S. Geological Survey, 2011a). These same features 

that form in springs also result in an aquifer that is susceptible 

to contamination because storm-water runoff is quickly transferred to the subsurface (Ryan and Meiman, 1996).

Purpose and Scope

The purpose of this report is to document the results of 

hydrogeologic mapping between 2011 and 2012 in the GRSP 

and HCSNA. This report presents the first detailed 1:24,000 

geologic map, and proposed names and descriptions of the 

hydrostratigraphic units in the study area. The mapping also 

provided an opportunity to determine if hydrogeologic characteristics of the Trinity aquifer rocks, located south of the study 

area in northern Bexar County (fig. 1; Clark and others, 2009), 

would be correlative in western Kendall and eastern Comal 

Counties. In addition, the report contains information on 

lithostratigraphy and hydrostratigraphy of the Hammett Shale, 

Cow Creek Limestone, Hensell Sand, and the lower member 

of the Glen Rose Limestone. Detailed hydrostratigraphic 

mapping of GRSP and HCSNA will aid the Texas Parks and 

Wildlife Department and other water managers in determining 

the effects and future development of groundwater resources 

in the study area. This study focuses on the outcrops of the 

Trinity aquifer rocks within the boundaries of the two parks.

Description of the Study Area

The study area is located in eastern Kendall and western 

Comal Counties, south-central Texas, about 25 miles (mi) north 

of the city of San Antonio (fig. 1). The study area contains 

approximately 4,230 contiguous acres of land that are almost 

evenly divided between GRSP, encompassing 46% of the study 

area (Texas Parks and Wildlife Department, 2012a); and the 

adjoining HCSNA, encompassing 54% of the study area (Texas 

Parks and Wildlife Department, 2012b; pl. 1). The Guadalupe 

River flows through the northern part of the study area and 

forms parts of the eastern and western park borders (fig. 1, 

photograph 1). The Guadalupe River’s mean flow obtained 

from 8.5 river-miles downstream from the eastern boundary of 

the study area (USGS site number 08167500; http://waterdata.

usgs.gov/tx/nwis/uv/?site_no=08167500&PARAmeter_cd=00

065,00060,00062,72020,00054, accessed April 2, 2014), was 

373 cubic feet per second (cfs). 

The study area is characterized by steep-sided, narrow 

valleys, many of which contain seeps and springs. The 

drainage pattern is predominantly dendritic, although trellis 

patterns occur where faults and fractures control the drainage. 

These valleys have cut into the tableland of the Edwards 

Plateau (fig. 2) and contain tributaries that drain to the 

Guadalupe River.

The lower reach of Honey Creek is a spring-fed (George, 

1952), perennial (Musgrove and others, 2010) tributary of the 

Guadalupe River. The spring flows from Honey Creek cave, a 

subsurface trellis cave system with long passages aligned in a 

southwest to northeast direction that is connected by shorter, 

cross-passages aligned in a southeast to northwest direction 

(George, 1952; Elliott and others, 1994). This cavern is the 

longest known cave in Texas with over 20 mi of mapped passages (Elliott, 2012). Honey Creek cave is not shown on the 

map, because it is outside the boundaries of the study area on 

private property. In addition, the cave location is not shown 

because of safety concerns; the cave contains flooded passages 

and reacts quickly to rain events and has the potential of 

trapping inexperienced explorers. 
Geologic Framework 3

Methods of Investigation 

A geophysical well-log near the study area was correlated 

with geophysical logs from northern Bexar County. The units 

used herein were first identified during the analysis of geophysical logs and two borehole rock-cores from wells in northern Bexar County (fig. 3) by the senior authors of this study. 

The cores from northern Bexar County are currently stored at 

the USGS Core Research Center, Denver, Colo.

The field mapping was aided by an Apple iPad2, which 

contained geospatially registered 7.5′ USGS topographic 

maps and an integrated global positioning system. Attitudes 

of fractures and faults were measured using either a handheld 

compass or the iPad2 compass application, called GeoId. 

Data collected with the iPad2 was verified with a handheld 

compass. Bedding attitudes in the study area were horizontal 

or nearly horizontal, and are therefore not shown on the map. 

The field data were transferred to Esri ArcMap geographic 

information system (GIS), quality checked, and then used to 

produce the geologic map (pl. 1).

Lithologic and hydrostratigraphic descriptions are based 

on field observations as well as previously published reports, 

such as Stricklin and others (1971) and Amsbury (1974). 

Lithologic descriptions are based on Dunham’s (1962) carbonate rock classification system that characterizes carbonate 

rocks based on their fabric. The fabric of a rock is defined as, 

“The orientation in space of the particles, crystals, and cement 

of which a sedimentary rock is composed” (Bates and Jackson, 

1987, p. 232). The porosity of the rocks is identified as either 

fabric selective or not-fabric selective under the sedimentary 

carbonate rock classification system (table 1) of Choquette and 

Pray (1970). According to Choquette and Pray, porosity that 

develops because of textural and structural features of the rock 

is classified as fabric selective. If there is no relation between 

the porosity and fabric elements, the porosity is classified as 

not-fabric selective (table 1).

Faults shown on the geologic map are based on observed 

and inferred stratigraphic offsets; however, no fault planes 

were seen in the outcrop. Fractures depicted on the map 

are labeled as such because of the unusually long distances 

these fractures can be traced. The fractures do not show any 

displacement or stratigraphic offset, which is in contrast to the 

mapped faults. Strike and dip of fractures were also noted, and 

were imported into the Grapher v. 9 software package (Golden 

Software, Inc., 2003) to create a rose diagram (fig. 4).

Geologic Framework

Sediments that compose the Trinity Group rocks were 

deposited during the Early Cretaceous (table 1) on a large 

shallow-water platform that sloped to the south and southeast, away from the Llano Uplift. The southeastern edge of 

the uplift is about 30 mi to the north of the study area. The 

Llano Uplift was aerially to subaerially exposed, and was a 

topographic high that supplied sediment to the ancestral Gulf 

of Mexico. The Trinity Group was deposited as a sequence of 

three, transgression-regression, clastic carbonate “couplets” 

on the shallow-water platform (Clark, 2004; Weirman and 

others, 2010). The three transgression-regression “couplets” 

include—(1) the deposition of the Hosston and Sligo Formations (not exposed in the study area; Imlay, 1940); (2) the 

deposition of the Hammett Shale and Cow Creek Limestone; 

and (3) the deposition of the Hensell Sand and Glen Rose 

Limestone (Clark, 2004; Weirman and others, 2010; table 1). 

These rock units contain shale, grainstone, sandstone, and 

fossiliferous limestone with alternating and interfingering 

mudstone, wackestone, packstone, and grainstone.

Lithostratigraphy

The stratigraphically, lowest mapped unit within the 

study area is the Pearsall Formation. The Pearsall Formation is 

composed of the Hammett Shale, Cow Creek Limestone, and 

Hensell Sand. The thickness of the Hammett Shale is based 

on geophysical logs and is estimated to be approximately 

50 feet (ft) thick. The lower 15 ft of the unit contain siltstone 

and dolomite. The upper 35 ft are primarily claystone with 

sandstone lentils at the base and middle parts of the unit, and 

fossiliferous dolomitic limestone in the uppermost part of the 

unit (Lozo and Stricklin, 1956; Weirman and others, 2010). 

The contact of the Hammett Shale with the overlying Cow 

Creek Limestone is conformable (Weirman and others, 2010). 

Although not observed, the Hammett Shale is inferred to exist 

in the topographically lower sections of the Guadalupe River 

valley and its tributaries, in the northeastern part of the map 

area, based on comparisons of stratigraphic thicknesses and 

elevation changes. The Cow Creek Limestone is approximately 72 ft thick in the study area. This thickness is based 

on a geophysical log of well DX–68–13–209 (fig. 3), located 

approximately 0.5 mi from the eastern boundary of the study 

area and about 2.5 mi southeast of the Cow Creek Limestone 

exposed along Honey Creek. Weirman and others (2010) 

subdivided the Cow Creek Limestone into a lower dolomitic 

unit and an upper grainstone unit, herein referred to as the 

lower member of the Cow Creek Limestone and upper 

member of the Cow Creek Limestone, respectively. 

The lower member of the Cow Creek Limestone is about 

14 ft thick based on the geophysical log of well DX–68–13–

209 (fig. 3), and is composed of dolomitic oyster mudstone to 

wackestone that grades upward to a dolomitic oyster wackestone to packstone (Weirman and others, 2010). In outcrop, 

the lower part of the Cow Creek Limestone is softer and more 

easily eroded, resulting in a cutback that is overlain by the 

more massive and resistant upper part (photograph 2). Field 

observations have revealed that a mostly bioturbated, recrystallized, dolomitic mudstone occurs near the contact of the 

lower and upper parts. 

The upper member of the Cow Creek Limestone is 

58 ft thick, based on both the geophysical log of well DX–68–

13–209 and field mapping. According to Weirman and others 

(2010), the upper member of the Cow Creek Limestone is a 
4 Geology and Hydrostratigraphy of Guadalupe River State Park and Honey Creek State Natural Area, TX

brown to white, very fine grained to fine grained carbonate 

sand grainstone with localized bedding. They also state that 

locally, the upper part is a white, well-sorted, fine- to mediumgrained carbonate sand grainstone that has been recrystallized. 

The top of the upper member of the Cow Creek Limestone 

contains depositional, trough cross-bedding (Weirman and 

others, 2010). The upper contact of the Cow Creek Limestone 

with the overlying Hensell Sand is considered to be unconformable (Weirman and others, 2010). 

The Hensell Sand is approximately 40 ft thick in the 

study area; however, the geophysical log (fig. 3) from well 

DX–68–13–209 indicates that the unit is 70 ft thick in the 

subsurface, which correlates with its observed thickness in 

wells south of the study area in northern Bexar County (fig. 1). 

In its lower part, the Hensell Sand is a reddish claystone and 

siltstone which contains terrigenous sandstone, pelecypods, 

and fossil fragments. The pelecypods in the Hensell Sand 

commonly have beekite structures on the surface of the shell. 

Beekite is a chalcedony pseudomorph occurring as small rings 

on the surface of shells (Gary and others, 1977). These oysters 

are evidently a common occurrence as they were observed at 

various sites where the Hensell Sand is exposed in the study 

area. In addition, George (1952, p. 16) also noted the occurrence of the fossil exogyra that “...have concentric surface 

markings of secondary siliceous material (beekite)” in two 

different levels of the Hensell Sand. The upper part of the 

Hensell Sand is a nodular, fine-grained sandstone that contains 

quartz and feldspar grains, fossil fragments, fish teeth, and 

pelecypods that also commonly show beekite structures. 

The Hensell Sand also contains quartz geodes, some of 

which are more than a foot in diameter. The quartz geodes 

appear to increase in abundance and size near the small igneous dike that is mapped in the northeastern part of the study 

area. The Hensell Sand conformably underlies the lower 

member of the Glen Rose Limestone (photograph 3), and 

commonly forms slopes between the Glen Rose Limestone 

and the underlying Cow Creek Limestone. Both the Glen Rose 

and the Cow Creek Limestones are more resistant to erosion 

and commonly form cliffs or ledges. 

The lower member of the Glen Rose Limestone is 

approximately 260 ft thick; however, within the study area the 

top of this formation has been eroded and only about 185 ft 

of the lower portion remain. This 185 ft remnant of the lower 

member of the Glen Rose Limestone was divided into three 

mappable unnamed lithostratigraphic units; which correlate 

to the three hydrostratigraphic units identified in the hydrostratigraphic section. The lower 55 ft section of the Glen Rose 

Limestone contains a very thick to massive bed of a Toucasia 

sp. grainstone. The lower part of the unit commonly contains 

shell fragments, pecten, Turritella, and oyster species. At one 

location, a biostrome of unidentified coral crops, located above 

the base of the lower member of the Glen Rose Limestone, 

was traced laterally several hundred feet. The location of the 

biostrome is not shown to protect the site from collectors.

Above the lower massive bed of Toucasia sp. is approximately 70 ft of alternating marl and mudstone. This 70 ft unit 

is covered by soil and vegetation; however, ledges containing 

miliolid grainstone, grainstone, nodular bioturbated wackestone, and monoplurids protrude through the soil. Throughout 

this unit, pectens, oysters, pelecypods, Nerinia sp., Orbitolina

sp., Tylostoma sp., and monoplurids can be found. Above the 

alternating beds of marl and mudstone is a massive limestone 

that forms cliffs at several locations. This massive limestone 

contains packstone to grainstone and fossil fragments. The 

massive limestone is overlain by alternating beds of marl and 

limestone. Collectively, the massive limestone and overlying 

marl and limestone are as much as 60 ft thick in the study area. 

Hydrostratigraphy

Hydrostratigraphic units have been mapped using the 

porosity-based classification system developed by Choquette 

and Pray (1970). According to Choquette and Pray, porosity 

that develops as a result of textural and structural features of 

the rock is classified as “fabric selective.” If there is no relation between the porosity and fabric elements, the porosity is 

classified as “not-fabric selective.” To characterize the hydrostratigraphic units shown on the map, only primary porosity 

types were used. The primary fabric selective porosity types 

identified in the study area are interparticle, moldic, burrowed, 

and bedding plane porosity. The primary not-fabric selective 

porosity types are fracture, channel, vug, or cave porosity.

These hydrostratigraphic units were observed in geophysical logs of boreholes in northern Bexar County that 

penetrated the middle Trinity aquifer (fig. 3, table 1). The 

middle Trinity aquifer encompasses the lower member of the 

Glen Rose Limestone, the Hensell Sand and the Cow Creek 

Limestone from top to bottom (Ashworth, 1983) and ranges in 

thickness from 284 to 327 ft in the study area. In the northern 

Bexar County area, the lower member of the Glen Rose Limestone could be divided into six hydrostratigraphic units from 

top to bottom, A through F. However, due to erosion, only a 

portion of hydrostratigraphic unit D and all of units E and F 

remain in the study area. The other hydrostratigraphic units are 

composed of the Hensell Sand, Cow Creek Limestone and the 

Hammett Shale. The current mapping effort did not subdivide 

the Hensell Sand, Cow Creek Limestone or Hammett Shale. 

The Hensell Sand, Cow Creek Limestone and Hammett Shale 

are referred to without their lithologic modifiers to differentiate between lithostratigraphic and hydrostratigraphic units. 

New names for the previously lettered D, E, and F units are 

herein proposed, based on topographic and historical features 

that are in the study area, and within those intervals. 

The Doeppenschmidt hydrostratigraphic unit (formerly 

subdivision D; Kgrd) is the uppermost hydrostratigraphic 

unit present, and contains interparticle, moldic, burrowed, 

bedding plane, fracture, and cave porosity. This interval might 

be an aquifer in the subsurface based on identified lithology, 

porosity, and the presence of seeps and springs. The Doeppenschmidt unit was named after the Doeppenschmidt family 

and homestead, who were the original settlers of the land that 
Geologic Framework 5

would later become Honey Creek State Natural Area (Texas 

Parks and Wildlife Department, 2012b). Water for the Doeppenschmidt homestead issued from a spring(s) at the base of 

the unit.

The Rust hydrostratigraphic unit (Kgrr) directly underlies the Doeppenschmidt unit, and has interparticle, fracture, 

and cave porosity. This hydrostratigraphic unit appears to be 

a barrier to subsurface flow, because springs and seeps flow 

from near its contact with the overlying Doeppenschmidt unit. 

Fracture porosity is not well developed in this unit because 

of the high marl content, but several of the thicker limestone 

beds have well developed fractures that may have undergone 

solution enlargement. The Rust unit contains cave porosity 

primarily near faults (pl. 1). The Rust unit was named for the 

Rust homestead in GRSP.

The Honey Creek hydrostratigraphic units (Kgrhc; 

photograph 4) is the lowest hydrostratigraphic interval in the 

lower Glen Rose Limestone, and contains interparticle, moldic 

(photograph 5), burrowed, bedding plane, fracture, channel, 

and cave porosity. A few feet above the base of this massive 

lower section is a ~1–2 ft thick band with conspicuous moldic 

porosity. This hydrostratigraphic unit is water-bearing in the 

subsurface and exhibits well developed porosity and permeability. The Honey Creek cave system, which is the longest 

explored cave system in Texas at over 20 mi (Texas Speleological Survey, 2012), discharges water into Honey Creek 

from this hydrostratigraphic unit. The unit was named for 

Honey Creek Cave. 

The Hensell hydrostratigraphic unit (Kheh) contains 

primarily interparticle porosity in its upper part. Moldic and 

cave porosity can be found throughout the unit. The cave 

porosity is likely associated with roof collapse of one or more 

underlying caves in the Cow Creek unit. This unit consists 

mostly sand suggesting it is most likely is a water-bearing 

unit in the subsurface. The Hensell unit was named for the 

Hensell Sand.

The Cow Creek hydrostratigraphic unit (Kcccc; photographs 6 and 7) contains interparticle, moldic, vug, burrowed, 

fracture, bedding plane, and channel, and cave porosity. This 

hydrostratigraphic unit is water-bearing in the subsurface and 

is the primary interval for water-well drilling in the area. The 

Cow Creek unit was named for the Cow Creek Limestone.

The Hammett hydrostratigraphic unit (Khah) is not 

exposed in the study area; however, it is shown on the map 

where it is inferred to underlie thin, unmapped alluvium and 

colluvium along the Guadalupe River. The interval is a confining unit based on field observations and data reported by 

Ashworth (1983) and Weirman and others (2010), which 

restricts the downward migration of groundwater resulting 

in springs forming near the base of the overlying Cow Creek 

unit. These springs contribute to the base flow that supplies the 

Guadalupe River with water over periods of low rainfall. The 

Hammett unit was named for the Hammett Shale lithostratigraphic unit.

Structural Features

Faulting and fracturing in the study area are part of the 

Miocene Balcones fault zone (BFZ). This fault zone is thought 

to be an extension of the Ouachita structural belt which underlies most of central Texas (Caran and others, 1982). The BFZ 

is an extensional system of faults that generally trends southwest to northeast in south-central Texas. These normal faults 

are en echelon in outcrop and dip to the southeast. Variation 

in the strikes and dips of the faults in the outcrop is a result of 

stress-strain variations of the different rocks that are faulted 

(Clark, 2004).

A rose diagram, which is a circular histogram plot of 

directional data and frequency, was generated for 84 measured 

fractures (fig. 4). The primary fracture orientation is northeast

to southwest and averages about 45 degrees, conjugate fractures were at 150 degrees which is consistent with the BFZ. 

These values for the primary and conjugate fractures are 

consistent with Wermund and others (1978) who derived the 

regional distribution of fractures for most of the BFZ using 

controlled aerial photograph mosaics. A second set of fractures trend 113 degrees and 68 degrees, and are most likely 

related to intrusion of the igneous dike, changes or variations 

in primary BFZ faulting, or possible karst collapses. The four 

fractures shown on the map (pl. 1) are composed of abundant 

parallel fractures that can be followed on the ground for the 

length of the trace indicated on the map. A comparison of the 

surface drainage patterns and mapped cave passages of Honey 

Creek Cave (not shown in report) suggest that the BFZ-related 

fractures and faults (45 degrees) may form the primary pathways for both surface and groundwater flow. The conjugate 

fractures (150 degrees) might form the link between the 

primary flow paths, allowing water to move from one drainage/conduit to the next parallel passage in a networking 

drainage pattern.

The igneous dike of Early Cretaceous age or younger 

cuts through the center of the study area near the confluence of 

Honey Creek and the Guadalupe River (photograph 8, pl. 1). 

The dike penetrates the Cow Creek Limestone and the lower 

part of the Hensell Sand, and is visible at three locations. The 

best exposure is in the Cow Creek Limestone along Honey 

Creek, approximately 300 ft upstream from the confluence 

of the creek with the Guadalupe River (photograph 8). At 

this location, the dike is columnar jointed and appears to be 

dipping slightly to the north. The actual dip of the dike is not 

possible to determine based on surface observations because 

weathering resulted in more of a transitional contact with the 

Cow Creek Limestone. Quartz geodes (photograph 9) are 

common throughout the Hensell Sand, but become more 

abundant near the dike. 
6 Geology and Hydrostratigraphy of Guadalupe River State Park and Honey Creek State Natural Area, TX

Summary

This report presents the first detailed 1:24,000 geologic 

map, and proposes names and descriptions of the hydrostratigraphic units in Guadalupe River State Park and Honey CreekState Natural Area, Kendall and Comal Counties, Texas. The 

newly defined hydrostratigraphy was based on the amount 

and type of porosity in each lithostratigraphic unit. The 

amount and type of porosity varies depending on the unit’s 

depositional environment, lithology, structural history, 

and diagenesis. 

The rocks exposed in the study area are Early Cretaceous 

sedimentary rocks that belong to the Trinity Group. These 

formations contain shale, grainstone, sandstone, and fossiliferous limestone, with alternating and interfingering mudstone, 

wackestone, packstone, and grainstone. The hydrostratigraphic 

units were determined by mapping the lithostratigraphic units 

and applying porosity characteristics from the classification 

system developed by Choquette and Pray (1970). The assigned 

hydrostratigraphic unit names are based on and consistent with 

topographic or historical features that occur in the study area. 

South of the study area, the lower member of the Glen 

Rose Limestone was divided into six hydrostratigraphic units 

based on geophysical logs and borehole core analysis. In the 

study area, erosion has removed the upper three and part of the 

fourth hydrostratigraphic unit. The remaining portion of the 

lower Glen Rose Limestone was divided into three hydrostratigraphic units, the Doeppenschmidt, Rust, and Honey Creek. 

The Doeppenschmidt unit (Kgrd) is the uppermost hydrostratigraphic unit present in the study area, and is characterized by 

interparticle, moldic, burrowed, bedding plane, fracture, and 

cave porosity. The Rust unit (Kgrr) has interparticle, fracture,

and cave porosity; however, it appears to be a confining unit 

because springs and seeps flow from near the contact with the 

overlying Doeppenschmidt unit. The Honey Creek hydrostratigraphic unit (Kgrhc) contains interparticle, moldic, 

burrowed, bedding plane, fracture, channel, and cave porosity. The Honey Creek unit is water bearing in the subsurface 

and exhibits well-developed porosity and permeability. The 

Honey Creek Cave system, which is the longest explored cave 

(20 mi) in Texas resides in this unit and discharges water into 

Honey Creek. 

The Hensell unit (Kheh) contains primarily interparticle porosity in its upper part, it also contains some moldic 

and cave porosity in its lower parts. Based on field observations, this unit is probably water bearing. The Cow Creek unit 

(Kcccc) contains interparticle, moldic, vug, burrowed, fracture, bedding plane, channel, and cave porosity. It is a waterbearing interval in the subsurface and is the primary target for 

water-well drilling in the area. The Hammett unit (Khah) is 

not exposed in the study area, but is inferred to underlie parts 

of the Guadalupe River in the northern part of the map area 

based on field mapping, geophysical logs, and the presence of 

seeps and springs that issue from the flanks of the river channel. The Hammett Shale restricts the downward migration of 

groundwater, which results in seeps and springs issuing from 

the base of the overlying Cow Creek unit that augment the 

base flow of the Guadalupe River in periods of low rainfall.

Faulting and fracturing in the study area is part of the 

Miocene Balcones fault zone, which is an extensional system 

of faults that generally trend southwest to northeast in southcentral Texas. An igneous dike of Early Cretaceous age or 

younger cuts through the center of the study area near the confluence of Honey Creek and the Guadalupe River. The igneous 

dike cuts the Cow Creek Limestone and the lower part of the 

Hensell Sand, which is visible at three locations.

Acknowledgments

The authors thank Scott Taylor of the Texas Parks and 

Wildlife Department, Superintendent of Guadalupe River 

State Park and Honey Creek State Natural Area, and his staff 

for courtesies extended during field mapping. We also thank 

Dave Lidke, Marcus Gary, and Tom Judkins for their critical 

reviews.

References Cited

Amsbury, D. L., 1974, Stratigraphic petrology of lower and 

middle Trinity rocks on the San Marcos platform, southcentral Texas, in B. F. Perkins, ed., Aspects of Trinity 

Geology: Geoscience and Man, v. 8, p. 1–35.

Ashworth, J.B., 1983, Ground-water availability of the Lower 

Cretaceous formations in the Hill Country of south-central 

Texas: Texas Department of Water Resources Report 273, 

172 p. 

Ashworth, J.B., and Hopkins, Janie, 1995, Aquifers of Texas: 

Texas Water Development Board Report 345, 69 p. 

Barker, R.A., and Ardis, A.F., 1996, Hydrogeological framework of the Edwards-Trinity aquifer system, west-central 

Texas: U.S. Geological Survey Professional Paper 1421–B, 

61 p.

Barnes, V.E., 1974, Geologic atlas of Texas, San Antonio 

Sheet—Robert Hamilton Cuyler memorial edition: University of Texas–Austin, Bureau of Economic Geology, 1 sheet, 

scale 1:250,000. 

Barnes, V.E., 1976, Geologic atlas of Texas, Crystal City–

Eagle Pass sheet—Dolan Hoye Eargle memorial edition: 

University of Texas–Austin, Bureau of Economic Geology, 

1 sheet, scale 1:250,000.

Bates, R.L., and Jackson, J.A., eds., 1987, Glossary of Geology (3d ed.)—American Geological Institute: New York, 

N.Y., 576 p.
References Cited 7

Bebout, D.G., Budd, D.A., and Schatzinger, R.A., 1981, Depositional and diagenetic history of the Sligo and Hosston 

Formations (Lower Cretaceous) in south Texas: Austin, 

University of Texas, Bureau of Economic Geology Report 

of Investigations, no. 109, 70 p.

Caran, S. C., Woodruff, C. M., Jr., and Thompson, E. J., 1982, 

Lineament analysis and inference of geologic structure—

Examples from the Balcones/Ouachita trend of Texas, 

University of Texas–Austin, Bureau of Economic Geology 

Geological Circular 82-1, p. 59–69.

Choquette, P.W., and Pray, L.C., 1970, Geologic nomenclature 

and classification of porosity in sedimentary carbonates: 

American Association of Petroleum Geologists Bulletin, 

v. 54, no. 2, p. 207–250.

Clark, A.K., 2003, Geologic framework and hydrogeologic 

features of the Glen Rose Limestone, Camp Bullis Training 

Site, Bexar County, Texas: U.S. Geological Survey Scientific Investigations Report 2003–4081, 14 p., 1 pl., scale 

1:24,000.

Clark, A.K., 2004, Geologic framework and hydrogeologic 

characteristics of the Glen Rose Limestone, Camp 

Stanley Storage Activity Area, Bexar County, Texas: U.S. 

Geological Survey Scientific Investigations Map 2831, 

scale 1:24,000. 

Clark, A.R., Blome, C.D., and Faith, J.R., 2009, Map showing 

the geology and hydrostratigraphy of the Edwards aquifer 

catchment area, northern Bexar County, south-central Texas: 

U.S. Geological Survey Open-File Report 2009–1008, 

24 p., 1 pl.

Dunham, R.J., 1962, Classification of carbonate rocks according to depositional texture, in Ham, W.E., ed., Classification 

of Carbonate Rocks: American Association of Petroleum 

Geologists Memoir 1, p. 108–121.

Elliott, W.R., 2012, CAVES in Handbook of Texas Online: 

Texas State Historical Association, accessed August 08, 

2012, at http://www.tshaonline.org/handbook /online/

articles/rqc03.

Elliott, W.R., and Veni, G., eds., 1994, The caves and karst of 

Texas—1994 National Speleological Society Convention 

Guidebook: National Speleological Society, 342 p.

Gary, Margaret, McAfee, Robert, Jr., and Wolf, C.L., eds., 

1977, Glossary of Geology: Falls Church, Va., American 

Geological Institute, 805 p.

George, P.G., Mace, R.E., and Petrossian, Rima, 2011, Aquifers of Texas, Texas Water Development Board Report 380: 

Austin, Tex., 172 p.

George, W.O., 1952, Geology and ground-water resources of 

Comal County, Texas, with sections on surface-water supplies and chemical character of the water: U.S. Geological 

Survey Water Supply Paper 1138, 126 p.

Grapher v. 9, 2003: Golden Software, Inc., accessed May 28, 

2003, at http://www.goldensoftware.com/Products/grapher/

grapher.shtml.

Hanson, J.A., and Small, T.A., 1995, Geologic framework 

and hydrogeologic characteristics of the Edwards aquifer 

outcrop, Hays County, Texas: U.S. Geological Survey Water 

Resources Investigations Report 95–4265, 10 p.

Hill, R.T., 1891, The Comanche series of the Texas-Arkansas 

region: Geological Society of America Bulletin, v. 2, 

p. 503–528.

Imlay, R.W., 1940, Lower Cretaceous and Jurassic formation 

of southern Arkansas and their oil and gas possibilities: 

Arkansas Geological Survey Information Circular 12, 64 p.

Inden, R. F., 1974, Lithofacies and depositional model for a 

Trinity Cretaceous sequence, central Texas, in B. F. Perkins, 

ed., Aspects of Trinity Geology: Geoscience and Man, v. 8, 

p. 37–52.

Lozo, F.E., and Stricklin, F.L., Jr., 1956, Stratigraphic notes 

on the outcrop basal Cretaceous, central Texas: Gulf Coast 

Association of Geological Societies Transactions, v. 6, 

p. 67–78.

Lucia, F.J., 1995, Rock-fabric/petrophysical classification of 

carbonate pore space for reservoir characterization: American Association of Petroleum Geologists Bulletin, v. 79, 

no. 9, p. 1275–1300.

Mace, R.E., Chowdhury, A.H., Anaya, Roberto, and Way, S.C., 

2000, Groundwater availability of the Trinity Aquifer, Hill 

Country area, Texas—Numerical simulations through 2050: 

Texas Water Development Board Report 353: 

Austin, 111 p.

Maclay, R.W., 1995, Geology and hydrology of the Edwards 

Aquifer in the San Antonio area, Texas: U.S. Geological 

Survey Water-Resources Investigations Report 95–4186, 

64 p., 12 pl.

Mancini, E.A., and Scott, R.W., 2006, Sequence stratigraphy 

of Comanchean Cretaceous outcrop strata of northeast and 

south-central Texas—Implications for enhanced petroleum 

exploration: Gulf Coast Association of Geological Societies 

Transactions, v. 56, p. 539–550. 

Musgrove, M., Stern, L.A., and Banner, J.L., 2010, Springwater geochemistry at Honey Creek State Natural Area, central 

Texas—Implications for surface water and groundwater 

interaction in a karst aquifer: Journal of Hydrology, v. 388, 

p. 144–156.
8 Geology and Hydrostratigraphy of Guadalupe River State Park and Honey Creek State Natural Area, TX

Perkins, B.F., 1974, Paleoecology of a rudist reef complex in 

the Comanche Cretaceous Glen Rose Limestone of central 

Texas, in B. F. Perkins, ed., Aspects of Trinity Geology: 

Geoscience and Man, v. 8, p. 131–173.

Rose, P.R., 1972, Edwards Group, surface and subsurface, 

central Texas: University of Texas–Austin, Bureau of 

Economic Geology Report of Investigations RI–74, 198 p.

Ryan, Martin, and Meiman, Joe, 1996, An examination of 

short-term variations in water quality at a karst spring in 

Kentucky: Ground Water, v. 34, p. 23–30.

Stricklin, F.L., Jr., and Smith, C.I., 1973, Environmental 

reconstruction of a carbonate beach complex, Cow Creek 

(Lower Cretaceous) Formation of central Texas: Geological 

Society of America Bulletin, v. 84, no. 4, p. 1349–1368.

Stricklin, F.L., Jr., Smith, C.I., and Lozo, F.E., 1971, Stratigraphy of Lower Cretaceous Trinity deposits of central Texas: 

University of Texas–Austin, Bureau of Economic Geology 

Report of Investigations 71, 63 p.

Texas Parks and Wildlife Department, 2012a, Description of 

Guadalupe River State Park, accessed April 30, 2012, at 

http://www.tpwd.state.tx.us/state-parks/guadalupe-river/

park_history.

Texas Parks and Wildlife Department, 2012b, Description 

of Honey Creek Natural Area, accessed April 30, 2012, 

at http://www.tpwd.state.tx.us/state-parks/honey-creek/

park_history.

Texas Speleological Survey, 2012, Overview of Texas Caves 

and Karst, accessed March 28, 2012, at http://www.utexas.

edu/tmm/sponsored_sites/tss/cavesandkarst/index.html.

U.S. Geological Survey, 2011a, USGS groundwater information—What is karst, accessed April 11, 2011, at http://water.

usgs.gov/ogw/karst/pages/whatiskarst.

U.S. Geological Survey, 2011b, USGS water data reports, 

accessed August 6, 2011, at http://waterdata.usgs.gov/tx/

nwis/uv/?site_no=08167500&PARAmeter_cd=00065,00060,

00062,72020,00054

Warner, A.J., and Moody, J.S., 1992, West Raymond field 

[Mississippi]: Mississippi Geology, v. 13, no. 2, p. 13–22

Weirman, D.A., Broun, A.S., and Hunt, B.B., 2010, Hydrogeologic Atlas of the Hill Country Trinity Aquifer, Blanco, 

Hays, and Travis Counties, Central Texas: Prepared by the 

Hays-Trinity, Barton Springs/Edwards Aquifer, and BlancoPedernales Groundwater Conservation Districts, July 2010, 

17 pl. [DVD].

Wermund, E.G., 1996, Physiographic map of Texas: Bureau of 

Economic Geology Map SM0005, scale 1:6,336,000.

Wermund, E.G., Cepeda, J.C., and Luttrell, P.E., 1978, 

Regional distribution of fractures in the southern Edwards 

Plateau and their relationship to tectonics and caves: 

University of Texas–Austin, Bureau of Economic Geology 

Geological Circular, v. 78–2, 14 p.

Whitney, M.I., 1952, Some zone marker fossils of the Glen 

Rose Formation of central Texas: Journal of Paleontology, 

v. 26, no. 1, p. 65–73

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Clark and others— Geology and Hydrostratigraphy of Guadalupe River State Park and Honey Creek State Natural Area, TX—Scientific Investigations Map 3303

ISSN 2329-132X (online)

http://dx.doi.org/10.3133/sim3303