U.S. Geological Survey Scientific Investigations Map 3461 sheetFigure 11. Burrow porosity at the...
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Figure 11. Burrow porosity at the contact of hydrostratigraphic unit VIII of the Edwards aquifer (basal nodular member of the Edwards Group) and the cavernous hydrostratigraphic unit of the upper zone of the Trinity aquifer (Glen Rose Limestone of the Trinity Group), northern Medina County, Texas (photograph by Allan K. Clark, U.S. Geological Survey, May 23, 2018). Figure 10. Evaporitic beds of the cavernous hydrostratigraphic unit of the upper zone of the Trinity aquifer, northern Medina County, Texas (photograph by Allan K. Clark, U.S. Geological Survey, February 4, 2019). Figure 9. A sample of evaporite with vug and boxwork porosity in the cavernous hydrostratigraphic unit of the upper zone of the Trinity aquifer, northern Medina County, Texas (photograph by Allan K. Clark, U.S. Geological Survey, February 4, 2019). Figure 8. Channel porosity in the Devils River Limestone, northern Medina County, Texas (photograph by Allan K. Clark, U.S. Geological Survey, February 26, 2019). Figure 7. A high-angle fault juxtaposing the Glen Rose Limestone (Trinity Group) against the Devils River Limestone (informal dolomitic member) along Highway 173 (4.47 miles south of the Bandera and Medina County line), northern Medina County, Texas (photograph by Allan K. Clark, U.S. Geological Survey, December 4, 2019). Figure 6. Late Cretaceous igneous intrusive rocks exposed along County Road 241, northern Medina County, Texas (photograph by Allan K. Clark, U.S. Geological Survey, December 4, 2019). Figure 5. The Del Rio Clay (Washita Group), northern Medina County, Texas (photograph by Robert R. Morris, U.S. Geological Survey, July 18, 2019). Figure 4. Toucasia sp. (rudists) at the top of the Devils River Limestone, northern Medina County, Texas (photograph by Allan K. Clark, U.S. Geological Survey, July 7, 2019). 0 5 10 FEET 0 1 2 3 METERS 0 5 10 FEET 0 1 2 3 METERS APPROXIMATE SCALE APPROXIMATE SCALE Devils River Limestone Devils River Limestone Glen Rose Limestone Glen Rose Limestone FAULT FAULT BANDERA COUNTY BANDERA COUNTY BEXAR COUNTY Y T N U O C E D L A V U Y T N U O C E D L A V U Y T N U O C A N I D E M BEXAR COUNTY MEDINA COUNTY 2200 1957 37 471 2676 1796 1283 462 241 U V 211 U V 16 U V 173 San Antonio San Antonio San Antonio Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 60 feet 50 feet 90 feet 20 feet 40 feet 20 feet 40 feet 60 feet 60 feet 50 feet 50 feet t e e f 0 4 30 feet 60 feet 70 feet 90 feet 90 feet 10 feet 30 feet 20 feet 60 feet 80 feet 20 feet 40 feet 10 feet 10 feet 20 feet 20 feet 20 feet 20 feet 20 feet 30 feet 20 feet 30 feet 30 feet 40 feet 70 feet 130 feet 50 feet 50 feet 60 feet 60 feet 140 feet 90 feet 150 feet 30 feet 20 feet 10 feet 20 feet 40 feet 20 feet 60 feet 70 feet 60 feet 60 feet 20 feet 100 feet 160 feet 60 feet 80 feet 30 feet 80 feet 20 feet 20 feet 20 feet 20 feet 30 feet 20 feet 40 feet 70 feet 40 feet 120 feet 80 feet 100 feet 160 feet 20 feet 40 feet 60 feet 70 feet 40 feet 30 feet 180 feet 120 feet 70 feet C y p r e s s C r e e k C e d a r C r e e k M a r t i n C r e e k M i d d l e V e r d e C r e e k V e r d e C r e e k P a r k e r s C r e e k T i m b e r C r e e k I n d i a n S p r i n g C r e e k L i m e k i l n C r e e k D e e p C r e e k C o w C r e e k B u l l C r e e k H e x a C r e e k H o n d o C r e e k K o e n i g C r e e k South Fork San Geronimo Creek W e s t V e r d e C r e e k B a n d e r a C r e e k W a r d s C r e e k S p r i n g s C r e e k S e c o C r e e k L i t t l e S e c o C r e e k Little Comanche Creek R o c k y C r e e k B e a r S p r i n g C r e e k C a s c a d e C r e e k D r i p p i n g S p r i n g C r e e k M e d i n a R i v e r P o l e c a t C r e e k E l m C r e e k C y p r e s s Cr e ek C e d a r C reek M a r t i n C reek M i d d l e V er d e C r e e k V e rde Cr eek P a rke rs C r e e k T i m b e r Creek In d ia n Sp r in g Cre e k L i m e k i l n C re e k D e e p C r e ek C ow C r e e k B ull C r e e k Hex a C r e ek H on d o C r e e k Koe ni g Cr e ek South Fork San Geronimo Creek W e s t V erde C re e k Ba n de r a C r e e k W a r ds Cr e ek S p r i n gs C r eek S e c o C r e e k Littl e S ec o Creek Little Comanche Creek Ro c k y C re e k Bear Sp r ing C re e k C asc a d e C r e e k Drip p i n g S p r ing Creek M e d i n a R i v er Pol e ca t C r e e k E lm C r e e k Medina Lake Medina Lake Diversion Lake Diversion Lake Pecan Spring Indian Mound Springs Bear Spring Middle Spring Indian Spring Moccasin Spring Yellow Spring Richter Spring Twin Springs Bear Spring Pecan Spring Indian Mound Springs Bear Spring Middle Spring Indian Spring Moccasin Spring Yellow Spring Richter Spring Twin Springs Bear Spring HABY CROSSING FAULT DIV ERSIO N LAKE FAUL T MEDINA LAKE FAULT MEDINA LAKE FAULT PARKER CREEK FAULT WOODARD CAVE FAULT U D U D U D U D U D U D D U U D U D D U U D U D U D U D D U U D D U U D D U U D U D U D U D U D D U U D D U U D U D U D U D D U U D U D D U U D U D U D U D U D U D U D U D U D U D U D U D U D U D U D U D U D U D U D U D U D D U U D D U D U U D U D U D D U D U D U U D U D D U D U D U U D D U U D U D U D U D U D D U U D U D D U D U U D U D U D U D D U D U D U U D U D U D U D U D U D U D U D D U D U U D U D U D D U D U U D D U D U U D U D U D D U U D D U D U U D U D U D U D U D U D U D U D U D U D D U D U D U D U U D U D U D U D U D U D U D D U D U D U U D D U U D U D U D U D U D D U U D U D D U D U U D U D U D U D U D U D U D D U U D U D MEDINA DIVERSION LAKE DAM Base modified from U.S. Geological Survey 1:24,000-scale digital data Universal Transverse Mercator, zone 14 North American Datum of 1983 98°51'15" 99°01'30" 99°11'45" 99°22'00" 29°35'00" 29°24'45" 98°51'15" 99°01'30" 99°11'45" 99°22'00" 29°35'00" 29°24'45" SCALE 1:75,000 0 6 12 KILOMETERS 3 9 6 12 MILES 3 9 0 Igneous intrusive rock Fault, type unspecified—Dashed where inferred. U, upthrown; D, downthrown. Estimated vertical displacement at fault, in feet Contact—Between hydrostratigraphic units Facies transition line Approximate reservoir boundary Photograph location and identifier Spring—Direction of flow not indicated U D Figure 7 Figure 7 MAP EXPLANATION 10 feet Devils River Limestone Devils River Limestone (upper part) Devils River Limestone (lower part) I II III IV V VI VII VIII Cavernous Camp Bullis Upper evaporite Fossiliferous Lower evaporite Bulverde Little Blanco Twin Sisters Taylor Group (Pecan Gap Chalk) Austin Group Eagle Ford Group Buda Limestone Del Rio Clay Upper Glen Rose Limestone Upper confining unit (UCU) Lower Glen Rose Limestone Glen Rose Limestone Kainer Formation Person Formation Georgetown Formation Grainstone Kirschberg evaporite Dolomitic Basal nodular Cyclic and marine, undivided Leached and collapsed, undivided Regional dense member Upper Lower IIa Map abbreviation and color Member (formal and informal) Group or formation Hydrologic unit or informal hydrostratigraphic unit EXPLANATION OF HYDROSTRATIGRAPHIC UNITS Figure 3. Surficial extent of the rocks that compose the Edwards and Trinity aquifers within northern Medina County, Texas. 1 Informal. 2 Thickness range based on field mapping. 3 Informal, undivided. 4 The upper part of the Devils River Limestone thickens moving to the west off the San Marcos Platform facies and into the Devils River Trend. 5 Informal in the Kainer Formation and formal in the Fort Terrett Formation. 6 The fossiliferous hydrostratigraphic unit thins from the east to the west. Salinia texana bed immediately below Corbula bed, abundant fossils including Porocystis globularis, Orbitolina texana (Roemer, 1852), Macraster sp., Nerinia sp., pecten, gastropods, pelecypods Limestone and argillaceous limestone, fossils much more abundant than in the units above, Orbitolina minuta (Douglas, 1960) Weathers to an orangish red with a pebbly texture, often has less Juniperus ashei (cedar) growth and thicker grasses, boxwork and vug porosity, springs and seeps, often stock tanks in evaporite beds Alternating beds of limestone and argillaceous limestone, fossils rare, stairstep topography Massive, nodular and mottled limestone, BRBs and orange wisps, Ceratostreon [Exogyra] texana, regional white grainstone bed at the top of the unit, seeps and springs, ferns growing near contact of underlying unit Massively bedded light gray, Requieniidae, abundant Heavily bioturbated, evaporite beds, rhizoconcretions (root fossils), caves Crossbedded, ripple marks, miliolid grainstone Boxwork porosity with neospar and travertine frame Clay, holds water (stock tanks), fossiliferous; Ilymatogyra arietina Holds water (stock tanks), black dendrites, iron nodules and staining, Plesioturrilites brazoensis, Waconella wacoensis Thin graded cycles; massive beds to relatively thin beds; crossbeds, Caprinidae Bioturbated iron-stained beds separated by massive limestone beds; stromatolitic limestone, Montastrea roemeriana Wispy iron stains, thin bedded, in Devils River Limestone sometimes capped with oolitic limestone, often white in aerial photographs Porcelaneous limestone with calcite-filled veins, bluish dendrites Brownish-red sand, thin flagstones; petroliferous White, chalky limestone; Gryphaea aucella, Inoceramus sp. Yellow clay, blue clay in freshly dug exposure; large Exogyra ponderosa Weathers to an orangish red with a pebbly texture, often has less Juniperus ashei (cedar) growth and thicker grasses, boxwork and vug porosity, springs and seeps, often stock tanks in evaporite beds, Corbula sp. at base Limestone beds thicker and more resistive to erosion than overlying and underlying units, Orbitolina texana (Roemer, 1852), patch reefs Thick argillaceous beds, thin shale beds, Orbitolina texana (Roemer, 1852), contains ponds and seeps Caprinid biostrome, limestone, argillaceous limestone, Orbitolina minuta (Douglas, 1960) None IP, MO, FR, BP, CH, CV IP, FR, BP FR None MO, BU, VUG, BP, FR, BR, CV FR, CV IP, IG, BU, FR, BP, CV IG, MO, VUG, FR, BR, CV IP, IG, MO, BU, VUG, FR, BP, CV IP, MO, BU, BP, FR, CV MO, BR, BP, FR, CV BU, BP, FR, CV (occasional) IP, MO, BU, BR MO, BU, FR IP, MO, BU, BR MO, BR, BP, FR MO MO, BU, BP, FR IP Confining unit Confining unit Confining unit Confining unit Confining unit Confining unit Confining unit Confining unit, locally water bearing in cavernous zones Aquifer Aquifer Aquifer Aquifer Aquifer, confining unit in areas without caves Aquifer Aquifer Semiconfining unit Semiconfining unit Semiconfining unit Semiconfining unit Aquifer 230–540 130–160 20–40 40–50 50–60 80–90 70–90 20–24 40–60 50–60 90–140 10 8–10 30–40 2–20 100–120 6 120–140 90–140 150–250 4 40–60 30–40 30–70 30–50 70–90 * * * * * II III IV V VI VII VIII Cavernous Camp Bullis Upper evaporite Lower evaporite I Bulverde IIa Fossiliferous Little Blanco s r e t s i S n i w T Upper confining unit to the Edwards aquifer Middle zone of the Trinity aquifer Upper zone of the Trinity aquifer Edwards aquifer r e f i u q a y t i n i r T Kb Kdr Kpcm Kplc Kprd Kkg Kkke Kkd Kkbn Kgrle Kpg Kgrf Kgrcb Kgrc Kgrb Kgrue Kdrvlbn Kdrvld Kdrvlke Kdrvlg Kdrvu Kdrvurd Kgrlb Kgrts Kgrlf Kgruf Kg Kef Ka Fossiliferous blue-green to yellow-brown clay, packstone, iron nodules; Ilymatogyra arietina Dense, shaly, mudstone, wackestone, oyster-shell mudstone and wackestone; iron stained, chert Pelletal limestone, mudstone, miliolid grainstone, packstone, chert (bedded and large nodules); Caprinidae, crossbedded Reddish-brown, gray to light-tan shaly mudstone and wackestone, black dendrites, iron nodules, iron stained; Plesioturrilites brazoensis, Waconella wacoensis Brown, flaggy, sandy shale and argillaceous limestone; iron nodules; Inoceramus sp., shark teeth, fossil fragments; petroliferous odor Massive, chalky, locally argillaceous, mudstone, nodular wackestone, nodular bioturbated wackestone; Gryphaea aucella, Inoceramus sp.; volcanic and terrigenous clastics, calcite Argillaceous limestone, calcareous clay, blue in the subsurface weathers greenish yellow; fossils, large Exogyra ponderosa Recrystallized limestone, mudstone, wackestone, packstone, grainstone; chert (bedded and large nodules); iron stained, stromatolitic, Requieniidae, Montastrea roemeriana, oysters Miliolid, skeletally fragmented grainstone, mudstone, wackestone; chert (beds and nodules); crossbedded and ripple marked Highly altered crystalline limestone, chalky mudstone, occasional grainstone associated with tidal channels; chert (beds and nodules); coarse-grained spar, breccia and travertine, dissolution has removed all evaporites in the study area Chert (absent in lower 20 feet), dolomitic mudstone, wackestone, packstone, grainstone Shaly, nodular limestone, burrowed mudstone, wackestone, packstone, miliolid grainstone, dolomite, BRBs; Caprinidae, Ceratostreon [Exogyra] texana, Miliolidae, gastropods Evaporites (dissolved at surface), wackestone, packstone, miliolid grainstone, argillaceous limestone, dolomitic limestone; heavily bioturbated, occasional dinosaur tracks Alternating beds of wackestone, packstone, miliolid grainstone, argillaceous limestone; burrowed Evaporites (dissolved at surface), highly altered crystalline limestone and chalky mudstone; breccia, boxwork voids Evaporites (dissolved at surface), highly altered crystalline limestone and chalky mudstone; breccia, boxwork voids; Corbula beds Wackestone, grainstone, argillaceous wackestone, shale, evaporites (dissolved at surface); Monopleuridae, Requieniidae, Macraster sp., Nerinia sp., Orbitolina texana (Roemer, 1852), Porocystis globularis, Salenia texana, gastropods, pecten, and pelecypods Buff to light-gray, dense nodular mudstone and wackestone, calcite-filled veins, bluish dendrites, iron nodules, iron stained; shell fragments Alternating wackestone, packstone, miliolid grainstone, argillaceous limestone, mudstone, silty mudstone at base; Caprinidae, Monopleuridae, Requieniidae, Hemiaster sp., Neithea sp., Orbitolina minuta (Douglas, 1960), Porocystis globularis, Protocardia texana, Tapes decepta, Turritella sp., gastropods, mollusks Mudstone to grainstone, framestone, boundstone chert (bedded and large nodules); Caprinidae, Requieniidae, Montastrea roemeriana Upper Lower Mudstones, wackestone, argillaceous wackestone, boundstone; Orbitolina texana (Roemer, 1852), Caprinidae, Monopleuridae, and Requieniidae, gastropods, pectens, and pelecypods Argillaceous wackestone, shale; Orbitolina texana (Roemer, 1852), gastropods, pelecypods Taylor Pecan Gap Chalk * Austin * * Eagle Ford * * Buda Limestone * Del Rio Clay * Cyclic and marine 3 Leached and collapsed 3 Regional dense 1 Grain- stone 1 Kirschberg evaporite 5 Dolomitic 1 Basal nodular 1 * Lower Cretaceous Trinity Upper Glen Rose Limestone Kainer Formation Fort Terrett Formation Edwards Person Formation Georgetown Formation Late Cretaceous Washita Lower part of the Devils River Limestone Upper part of the Devils River Limestone Early Cretaceous Devils River Limestone Igneous Large amount of chert, Caprinidae chert containing fossils including Caprinidae, recrystallized limestone Period Epoch Group Formation Member (formal and informal) Lithology t i n u c i g o l o r d y H c i h p a r g i t a r t s o r d y H t i n u 1 Thickness 2 of outcrop in the study area (in feet) Hydrologic function Porosity type Field identification Map abbreviation and color Geologic framework Hydrostratigraphy [Period, Epoch, group, formation, formal and informal members, and lithology modified from Shumard (1860), Hill (1887, 1888, 1891, 1892), Hill and Vaughan (1898), Vaughan (1900a, b), Udden (1907), Adkins (1932), Stenzel (1938), Wilmarth (1938), Hazzard (1939), Ross (1943), Lozo and Stricklin (1956), Stricklin and others (1971), Rose (1972), Inden (1974), Perkins (1974), Stein and Ozuna (1995), Small and Clark (2000), Clark (2003), Clark and others (2009, 2016b), and the U.S. Geological Survey National Geologic Map Database (March 5, 2020), Geolex ( https://ngmdb.usgs.gov/Geolex/search); *no further subdivision; Orbitolina minuta (Douglas, 1960), Orbitolina texana (Roemer, 1852); BRBs, spherical textural features locally known as black rotund bodies (Maclay and Small, 1986); aquifers from Maclay and Small (1976), Ashworth (1983); thickness from outcrop, Clark (2003), Clark and others (2009, 2016b); hydrogeologic function modified from outcrop, Stein and Ozuna (1995), Small and Clark (2000), Clark (2003), Clark and others (2009, 2016b); carbonate classification from Dunham (1962) and Wright (1992); porosity types modified from Choquette and Pray (1970); fabric selective: IP = interparticle porosity, MO = moldic porosity, BP = bedding plane porosity, BU = burrowed porosity, IG = intergranular porosity; not fabric selective: FR = fracture porosity, CH = channel porosity, CV = cave porosity, VUG = vug porosity, BR = breccia] Figure 2. Summary of geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within northern Medina County, Texas. San Marcos Platform Maverick Basin Devils River T ren d GARNER STATE PARK B l a n c o R i v e r L i t t l e B l a n c o R i v e r M e d i n a R i v e r G u a d a l u p e R i v e r M e d i n a R i v e r S a n A n t o n i o R i v e r C i b o l o C r e e k C i b o l o C r e e k G u a d a l u p e R i v e r P e d e r n a l e s R i v e r C o l o r a d o R i v e r B a r t o n C r e e k S a n M a r c o s R i v e r N u e c e s R i v e r L e o n a R i v e r S a b i n a l R i v e r F r i o R i v e r F r i o R i v e r H o n d o C r e e k Blanc o Ri ver Litt l e B lanc o R iver M e d i n a Riv er G u a da l u p e River M e din a R i ver S a n A n tonio River C ib olo C re e k C i b o l o Creek Gu a da l upe R i ver Ped e r nales River C o lorado R i v e r Ba r t o n C r e ek San M arco s R i ve r N u e c e s R i ver L e o n a R i ver S a b i n a l R i v e r F r i o R i ve r F r i o Ri v er H o n d o Cr e ek Johnson City Dripping Springs Castroville Bulverde Buda Boerne Blanco Bandera New Braunfels Wimberley Hondo Kyle Uvalde San Antonio San Marcos Sabinal A ustin Austin KENDALL COUNTY HAYS COUNTY COMAL COUNTY BLANCO COUNTY BANDERA COUNTY BEXAR COUNTY UVALDE COUNTY MEDINA COUNTY ATASCOSA COUNTY TRAVIS COUNTY REAL COUNTY GILLESPIE COUNTY KERR COUNTY LLANO COUNTY BURNET COUNTY WILLIAMSON COUNTY A L A V A Z Y T N U O C O I R F Y T N U O C WILSON COUNTY GUADALUPE COUNTY CALDWELL COUNTY BASTROP COUNTY EDWARDS COUNTY KINNEY COUNTY MAVERICK COUNTY LEE COUNTY KARNES COUNTY GONZALES COUNTY BELL COUNTY 10 20 5 15 MILES 0 10 20 5 15 KILOMETERS 0 97°30' 97°52'30" 98°15' 98°37'30" 99°00' 99°22'30" 99°45' 100°07'30" 30°22'30" 30°00' 29°37'30" 29°15' 28°52'30" Base modified from U.S. Geological Survey 1:100,000-scale digital data Universal Transverse Mercator, zone 14 North American Datum of 1983 Depositional provinces modified from Barker and Ardis, 1996 Aquifers from George and others, 2011 EXPLANATION Edwards aquifer Trinity aquifer Study area boundary Balcones fault zone (Maclay, 1995, fig. 2) OUACHITA STRUCTURAL BELT Austin San Antonio San Antonio Uvalde TEXAS BALCONES FAULT ZONE Trinity aquifer Edwards aquifer EDWARDS PLATEAU COMANCHE SHELF Maverick Basin San Marcos Platform San Marcos Platform Axis of San Marcos Arch Stuart City R ee f Trend Devils River Trend Modified from Maclay and Small, 1986, fig. 6, and Barker and Ardis, 1996, fig. 6 Study area boundary Study area boundary Figure 1. Location of the study area relative to the State of Texas, Medina County, the surficial extent of the rocks that compose the Edwards and Trinity aquifers, and the surficial extent of the Balcones fault zone. Printed on recycled paper ISSN 2329-XXXX (print) ISSN 2329-13XX (online) https://doi.org/10.3133/sim3461 Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225, 1–888–ASK–USGS Digital files available at https://doi.org/10.3133/sim3461 Suggested citation: Clark, A.K., Morris, R.E., and Pedraza, D.E., 2020, Geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within northern Medina County, Texas: U.S. Geological Survey Scientific Investigations Map 3461, 13 p. pamphlet, 1 pl., scale 1:24,000, https://doi.org/10.3133/sim3461. Geologic Framework and Hydrostratigraphy of the Edwards and Trinity Aquifers Within Northern Medina County, Texas By Allan K. Clark, Robert R. Morris, and Diana E. Pedraza 2020 Scientific Investigations Map 3461 Pamphlet accompanies map U.S. Department of the Interior U.S. Geological Survey I SBN 978- 1- 4113-4377- 1 9 781411 343771
Transcript of U.S. Geological Survey Scientific Investigations Map 3461 sheetFigure 11. Burrow porosity at the...
Figure 11. Burrow porosity at the contact of hydrostratigraphic unit VIII ofthe Edwards aquifer (basal nodular member of the Edwards Group) and thecavernous hydrostratigraphic unit of the upper zone of the Trinity aquifer(Glen Rose Limestone of the Trinity Group), northern Medina County, Texas(photograph by Allan K. Clark, U.S. Geological Survey, May 23, 2018).
Figure 10. Evaporitic beds of the cavernous hydrostratigraphicunit of the upper zone of the Trinity aquifer, northern MedinaCounty, Texas (photograph by Allan K. Clark, U.S. GeologicalSurvey, February 4, 2019).
Figure 9. A sample of evaporite with vug and boxwork porosity in thecavernous hydrostratigraphic unit of the upper zone of the Trinity aquifer,northern Medina County, Texas (photograph by Allan K. Clark,U.S. Geological Survey, February 4, 2019).
Figure 8. Channel porosity in the Devils River Limestone, northern MedinaCounty, Texas (photograph by Allan K. Clark, U.S. Geological Survey,February 26, 2019).
Figure 7. A high-angle fault juxtaposing the Glen Rose Limestone (TrinityGroup) against the Devils River Limestone (informal dolomitic member) alongHighway 173 (4.47 miles south of the Bandera and Medina County line),northern Medina County, Texas (photograph by Allan K. Clark,U.S. Geological Survey, December 4, 2019).
Figure 6. Late Cretaceous igneous intrusive rocks exposed along CountyRoad 241, northern Medina County, Texas (photograph by Allan K. Clark,U.S. Geological Survey, December 4, 2019).
Figure 5. The Del Rio Clay (Washita Group), northern MedinaCounty, Texas (photograph by Robert R. Morris, U.S. GeologicalSurvey, July 18, 2019).
Figure 4. Toucasia sp. (rudists) at the top of the Devils River Limestone,northern Medina County, Texas (photograph by Allan K. Clark,U.S. Geological Survey, July 7, 2019).
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DU
UD
DU
UD
U D
UD
UD
UD
D U
UD
DU
UD
UD
UD
UD
DU
UD
UD
DU
UD
UD
UD
UD
UD
UD
UD
UD
UD
UD
UD
U D
UD
UD
UD
UD
UD
UD
UD
UD
UD
DU
UD
DU
DU
UD
UD
UD
DU
DU
D U
U D
UD
DU
DU
DU
UD
DU
UD
UD
UD
UD
UD D
U
UD
UD
DU
DU
UD
UD
UD
UD
D UD U
D U
UD
UD U
D
UD
UD
UD
UD
U D
D U
DU
UD
U D
UD
DU
D U
UD
DU
DU
UD
UD
UD
D U
UD
DU
D U
UD
UD
UD
UD
UD
UD
UD
UD
UD
UD
DU
D U
DU
DU
UD
UD
UD
UD
UD
UD
UD
DU
DU
D U
UD
DU
UD
UD
UD
UD
UD
DU
UD
UD
DU
DU
UD
UD
UD
UD
UD
UD
UD
DU
UD
UD
MEDINADIVERSION
LAKEDAM
Base modified from U.S. Geological Survey 1:24,000-scale digital dataUniversal Transverse Mercator, zone 14North American Datum of 1983
98°51'15"
99°01'30"99°11'45"
99°22'00"
29°35'00"
29°24'45"
98°51'15"
99°01'30"
99°11'45"
99°22'00"
29°35'00"
29°24'45"
SCALE 1:75,000
0 6 12 KILOMETERS3 9
6 12 MILES3 90
Igneous intrusive rock
Fault, type unspecified—Dashed where inferred. U, upthrown; D, downthrown. Estimated vertical displacement at fault,in feet
Contact—Between hydrostratigraphic units
Facies transition line
Approximate reservoir boundary
Photograph location and identifier
Spring—Direction of flow not indicated
UD
Figure 7Figure 7
MAP EXPLANATION
10 feet
Dev
ils R
iver
Lim
esto
ne
Dev
ils R
iver
Lim
esto
ne(u
pper
par
t)
Dev
ils R
iver
Lim
esto
ne(lo
wer
par
t)
I
II
III
IV
V
VI
VII
VIII
Cavernous
Camp Bullis
Upper evaporite
Fossiliferous
Lower evaporite
Bulverde
Little Blanco
Twin Sisters
Taylor Group (Pecan Gap Chalk)
Austin Group
Eagle Ford Group
Buda Limestone
Del Rio Clay
Upper Glen RoseLimestone
Upperconfiningunit (UCU)
Lower Glen RoseLimestone
Glen RoseLimestone
KainerFormation
PersonFormation
GeorgetownFormation
Grainstone
Kirschberg evaporite
Dolomitic
Basal nodular
Cyclic and marine, undivided
Leached and collapsed,undivided
Regional dense member
Upper
Lower
IIa
Map abbreviation
and color
Member(formal and informal)
Group or formation
Hydrologic unitor informal
hydrostratigraphic unit
EXPLANATION OF HYDROSTRATIGRAPHIC UNITS
Figure 3. Surficial extent of the rocks that compose the Edwards and Trinity aquifers within northern Medina County, Texas.
1Informal.2Thickness range based on field mapping.3Informal, undivided.4The upper part of the Devils River Limestone thickens moving to the west off the San Marcos Platform facies and into the Devils River Trend.5Informal in the Kainer Formation and formal in the Fort Terrett Formation.6The fossiliferous hydrostratigraphic unit thins from the east to the west.
Salinia texana bed immediately below Corbula bed, abundant fossils including Porocystis globularis, Orbitolina texana
(Roemer, 1852), Macraster sp., Nerinia sp., pecten, gastropods, pelecypods
Limestone and argillaceous limestone, fossils much more abundant than in the units above,
Orbitolina minuta (Douglas, 1960)
Weathers to an orangish red with a pebbly texture, often has less Juniperus ashei (cedar)
growth and thicker grasses, boxwork and vug porosity, springs and seeps,
often stock tanks in evaporite beds
Alternating beds oflimestone and argillaceous
limestone, fossils rare, stairstep topography
Massive, nodular and mottled limestone, BRBs and orange wisps, Ceratostreon [Exogyra] texana, regional white grainstone bed at the
top of the unit, seeps and springs, ferns growing near contact of underlying unit
Massively bedded light gray,Requieniidae, abundant
Heavily bioturbated, evaporite beds, rhizoconcretions
(root fossils), caves
Crossbedded, ripple marks,miliolid grainstone
Boxwork porosity with neospar and travertine
frame
Clay, holds water (stock tanks),fossiliferous; Ilymatogyra arietina
Holds water (stock tanks),black dendrites, ironnodules and staining,
Plesioturrilites brazoensis,Waconella wacoensis
Thin graded cycles;massive beds to
relatively thin beds;crossbeds,Caprinidae
Bioturbated iron-stainedbeds separated bymassive limestonebeds; stromatolitic
limestone, Montastrea roemeriana
Wispy iron stains, thin bedded, in Devils RiverLimestone sometimes capped with oolitic
limestone, often white in aerial photographs
Porcelaneous limestonewith calcite-filled veins,
bluish dendrites
Brownish-red sand, thinflagstones; petroliferous
White, chalky limestone;Gryphaea aucella,
Inoceramus sp.
Yellow clay, blue clayin freshly dug exposure;
large Exogyra ponderosa
Weathers to an orangish red with a pebbly texture, often has less Juniperus ashei (cedar)growth and thicker grasses, boxwork and vugporosity, springs and seeps, often stock tanks
in evaporite beds, Corbula sp. at base
Limestone beds thicker and more resistive toerosion than overlying and underlying units,
Orbitolina texana (Roemer, 1852),patch reefs
Thick argillaceous beds, thin shale beds,Orbitolina texana (Roemer, 1852),
contains ponds and seeps
Caprinid biostrome, limestone,argillaceous limestone,
Orbitolina minuta (Douglas, 1960)
None
IP, MO,FR, BP,CH, CV
IP, FR,BP
FR
None
MO, BU,VUG, BP,FR, BR,
CV
FR, CV
IP, IG,BU, FR,BP, CV
IG, MO,VUG, FR,BR, CV
IP, IG,MO, BU,VUG, FR,BP, CV
IP, MO,BU, BP,FR, CV
MO, BR,BP, FR,
CV
BU, BP,FR,CV
(occasional)
IP, MO,BU, BR
MO, BU,FR
IP, MO,BU, BR
MO, BR,BP, FR
MO
MO, BU,BP, FR
IP
Confiningunit
Confiningunit
Confiningunit
Confiningunit
Confiningunit
Confiningunit
Confiningunit
Confining unit,locally water
bearing incavernous
zones
Aquifer
Aquifer
Aquifer
Aquifer
Aquifer,confining unit
in areaswithout caves
Aquifer
Aquifer
Semiconfiningunit
Semiconfiningunit
Semiconfiningunit
Semiconfiningunit
Aquifer
230–540
130–160
20–40
40–50
50–60
80–90
70–90
20–24
40–60
50–60
90–140
10
8–10
30–40
2–20
100–
1206
120–140
90–140
150–
2504
40–60
30–40
30–70
30–50
70–90
*
*
*
*
*
II
III
IV
V
VI
VII
VIII
Cave
rnou
sCa
mp
Bulli
s Up
per
evap
orite
Lo
wer
evap
orite
I
Bulv
erde
IIa
Foss
ilife
rous
Li
ttle
Blan
cosr et si S ni
wT
Uppe
r con
finin
g un
it to
the
Edw
ards
aqu
ifer
Mid
dle
zone
of t
he T
rinity
aqu
ifer
Uppe
r zon
e of
the
Trin
ity a
quife
rEd
war
ds a
quife
rrefiuqa ytinirT
Kb
Kdr
Kpcm
Kplc
Kprd
Kkg
Kkke
Kkd
Kkbn
Kgrle
Kpg
Kgrf
Kgrcb
Kgrc
Kgrb
Kgrue
Kdrv
lbn
Kdrv
ldKd
rvlk
eKd
rvlg
Kdrv
uKd
rvur
d
Kgrlb
Kgrts
Kgrlf
Kgru
f
Kg
Kef
Ka
Fossiliferous blue-green to yellow-brown clay, packstone, iron nodules;
Ilymatogyra arietina
Dense, shaly, mudstone, wackestone, oyster-shell mudstone and wackestone;
iron stained, chert
Pelletal limestone,mudstone, miliolid
grainstone, packstone, chert (bedded and large
nodules); Caprinidae, crossbedded
Reddish-brown, gray to light-tan shalymudstone and wackestone, black dendrites,iron nodules, iron stained; Plesioturrilites
brazoensis, Waconella wacoensis
Brown, flaggy, sandy shale and argillaceouslimestone; iron nodules; Inoceramus sp.,
shark teeth, fossil fragments; petroliferous odor
Massive, chalky, locally argillaceous, mudstone, nodular wackestone, nodular
bioturbated wackestone; Gryphaea aucella,Inoceramus sp.; volcanic andterrigenous clastics, calcite
Argillaceous limestone, calcareous clay,blue in the subsurface weathers greenishyellow; fossils, large Exogyra ponderosa
Recrystallized limestone, mudstone, wackestone, packstone, grainstone;
chert (bedded and large nodules); iron stained,
stromatolitic, Requieniidae,Montastrea roemeriana,
oysters
Miliolid, skeletally fragmented grainstone,mudstone, wackestone; chert (beds and
nodules); crossbedded and ripple marked
Highly altered crystalline limestone, chalkymudstone, occasional grainstone associatedwith tidal channels; chert (beds and nodules);coarse-grained spar, breccia and travertine,
dissolution has removed all evaporitesin the study area
Chert (absent in lower 20 feet), dolomitic mudstone, wackestone,
packstone, grainstone
Shaly, nodular limestone, burrowed mudstone, wackestone, packstone,miliolid grainstone, dolomite, BRBs;
Caprinidae, Ceratostreon [Exogyra] texana, Miliolidae, gastropods
Evaporites (dissolved at surface), wackestone, packstone, miliolid grainstone, argillaceous
limestone, dolomitic limestone; heavily bioturbated, occasional dinosaur tracks
Alternating beds of wackestone, packstone, miliolid grainstone,
argillaceous limestone; burrowed
Evaporites (dissolved at surface), highly altered crystalline limestone and chalky
mudstone; breccia, boxwork voids
Evaporites (dissolved at surface), highly altered crystalline limestone and chalky
mudstone; breccia, boxwork voids; Corbula beds
Wackestone, grainstone, argillaceous wackestone, shale, evaporites (dissolved
at surface); Monopleuridae, Requieniidae, Macraster sp., Nerinia sp., Orbitolina
texana (Roemer, 1852), Porocystis globularis, Salenia texana, gastropods,
pecten, and pelecypods
Buff to light-gray, dense nodular mudstoneand wackestone, calcite-filled veins, bluish
dendrites, iron nodules, iron stained;shell fragments
Alternating wackestone, packstone, miliolidgrainstone, argillaceous limestone,mudstone, silty mudstone at base;
Caprinidae, Monopleuridae, Requieniidae,Hemiaster sp., Neithea sp., Orbitolina
minuta (Douglas, 1960), Porocystisglobularis, Protocardia texana, Tapes
decepta, Turritella sp., gastropods, mollusks
Mudstone to grainstone, framestone, boundstone
chert (bedded and large nodules);
Caprinidae, Requieniidae,
Montastrea roemeriana
Uppe
rLo
wer
Mudstones, wackestone, argillaceouswackestone, boundstone; Orbitolinatexana (Roemer, 1852), Caprinidae,Monopleuridae, and Requieniidae,
gastropods, pectens, and pelecypods
Argillaceous wackestone, shale;Orbitolina texana (Roemer, 1852),
gastropods, pelecypods
Tayl
or
Peca
nGa
pCh
alk
*
Aust
in
* *
Eagl
e Fo
rd
* *
Bud
a L
imes
tone
*
Del R
ioCl
ay *Cy
clic
and
mar
ine3
Leac
hed
and
colla
psed
3 Re
gion
al
dens
e1 Gr
ain-
ston
e1
Kirs
chbe
rg e
vapo
rite5
Dolo
miti
c1B
asal
nod
ular
1*
Low
er
Cret
aceo
us
Trin
ity
Uppe
r
Glen
Ros
e Li
mes
tone
Kain
er F
orm
atio
nFo
rt Te
rret
t For
mat
ion
Edw
ards
Pers
on F
orm
atio
nGe
orge
tow
nFo
rmat
ion
Late
Cre
tace
ous
Was
hita
Low
er p
art o
f the
Dev
ils R
iver
Lim
esto
neUp
per p
art o
f the
Dev
ils R
iver
Lim
esto
ne
Early
Cre
tace
ous
Devi
ls R
iver
Lim
esto
ne
Igne
ous
Large amountof chert,
Caprinidae chertcontaining fossils
includingCaprinidae,
recrystallizedlimestone
Perio
d
Epoc
h
Grou
p
Form
atio
n
Mem
ber
(form
al a
ndin
form
al)
Lithology
tinu cigolordyH
cihpargitartsordyHtinu
1
Thickness2
of outcrop in the study area
(in feet)
Hydrologicfunction
Porositytype
Field identification
Map
abb
revi
atio
nan
d co
lor
Geologic framework Hydrostratigraphy
[Period, Epoch, group, formation, formal and informal members, and lithology modified from Shumard (1860), Hill (1887, 1888, 1891, 1892), Hill and Vaughan (1898), Vaughan (1900a, b), Udden (1907), Adkins (1932), Stenzel (1938), Wilmarth (1938), Hazzard (1939), Ross (1943), Lozo and Stricklin (1956), Stricklin and others (1971), Rose (1972), Inden (1974), Perkins (1974), Stein and Ozuna (1995), Small and Clark (2000), Clark (2003), Clark and others (2009, 2016b), and the U.S. Geological Survey NationalGeologic Map Database (March 5, 2020), Geolex (https://ngmdb.usgs.gov/Geolex/search); *no further subdivision; Orbitolina minuta (Douglas, 1960), Orbitolina texana (Roemer, 1852); BRBs, spherical textural features locally known as black rotund bodies (Maclay and Small, 1986); aquifers from Maclay and Small (1976), Ashworth (1983); thickness from outcrop, Clark (2003), Clark and others (2009, 2016b); hydrogeologic function modified from outcrop, Stein and Ozuna (1995), Small and Clark (2000), Clark (2003), Clark and others (2009, 2016b); carbonate classification from Dunham (1962) and Wright (1992); porosity types modified from Choquette and Pray (1970); fabric selective: IP = interparticle porosity, MO = moldic porosity, BP = bedding plane porosity,BU = burrowed porosity, IG = intergranular porosity; not fabric selective: FR = fracture porosity, CH = channel porosity, CV = cave porosity, VUG = vug porosity, BR = breccia]
Figure 2. Summary of geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within northern Medina County, Texas.
San Marcos Platform
Maverick Basin
Devils River Trend
GARNER STATE PARK
Blanco River
Little Blanco River
Medina River
Guadalupe River
Medina River
San Antonio River
Cibolo Creek
Cibolo Creek
Guadalupe River
Pedernales River
Colorado River
Bart on Creek
San Marcos River
Nueces River
Leona River
SabinalR iver
Frio R iver
Frio RiverHondo Creek
Blanco River
Little Blanco River
Medina River
Guadalupe River
Medina River
San Antonio River
Cibolo Creek
Cibolo Creek
Guadalupe River
Pedernales River
Colorado River
Bart on Creek
San Marcos River
Nueces River
Leona River
SabinalR iver
Frio R iver
Frio RiverHondo Creek
Johnson City
DrippingSprings
Castroville
Bulverde
Buda
Boerne
Blanco
BanderaNew
Braunfels
Wimberley
Hondo
Kyle
Uvalde
San Antonio
SanMarcos
Sabinal
AustinAustin
KENDALLCOUNTY
HAY
S C
OU
NTY
COMAL
COUNTY
BLANCOCOUNTY
BANDERACOUNTY
BEXAR COUNTY
UVALDECOUNTY MEDINA
COUNTYATASCOSACOUNTY
TRAV
ISCO
UNTY
REALCOUNTY
GILLESPIECOUNTY
KERRCOUNTY
LLANO COUNTY
BURN
ET C
OUN
TYW
ILLI
AMSO
NCO
UNTY
AL
AVAZ
YT
NU
OC
OIRF
YT
NU
OC
WIL
SON
COUNTY
GUADALUPECOUNTY
CALDWELL
COUNTY
BAST
ROP
COUN
TY
EDWARDSCOUNTY
KINNEYCOUNTY
MAVERICKCOUNTY
LEE
COUNTY
KARNES
COUNTY
GONZALE
SCOUNTY
BELL COUNTY
10 205 15 MILES
0 10 205 15 KILOMETERS
0
97°30'
97°52'30"
98°15'
98°37'30"
99°00'
99°22'30"
99°45'
100°07'30"
30°22'30"
30°00'
29°37'30"
29°15'
28°52'30"
Base modified from U.S. Geological Survey 1:100,000-scale digital dataUniversal Transverse Mercator, zone 14North American Datum of 1983
Depositional provinces modified from Barker and Ardis, 1996Aquifers from George and others, 2011
EXPLANATION
Edwards aquifer
Trinity aquifer
Study area boundaryBalcones fault zone
(Maclay, 1995, fig. 2)
OU
ACH
ITA
STRU
CTU
RAL
BELT
Austin
San AntonioSan AntonioUvalde
TEXASBALCONES FAULT ZONE
Trinity aquifer
Edwards aquifer
EDWARDS
PLATEAUC O M A N C H E S H E L F
MaverickBasin
San MarcosPlatform
San MarcosPlatform
Axis of SanMarcos Arch
Stuart City
Reef TrendDevils River Trend
Modified from Maclay and Small, 1986, fig. 6,and Barker and Ardis, 1996, fig. 6
Study area boundaryStudy area boundary
Figure 1. Location of the study area relative to the State of Texas, Medina County, the surficial extent of the rocks that compose the Edwards and Trinity aquifers, and the surficial extentof the Balcones fault zone.
Printed on recycled paper
ISSN 2329-XXXX (print)ISSN 2329-13XX (online)https://doi.org/10.3133/sim3461
Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government
For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225, 1–888–ASK–USGS
Digital files available at https://doi.org/10.3133/sim3461
Suggested citation: Clark, A.K., Morris, R.E., and Pedraza, D.E., 2020, Geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within northern Medina County, Texas: U.S. Geological Survey Scientific Investigations Map 3461, 13 p. pamphlet, 1 pl., scale 1:24,000, https://doi.org/10.3133/sim3461.
Geologic Framework and Hydrostratigraphy of the Edwards and Trinity Aquifers Within Northern Medina County, Texas By
Allan K. Clark, Robert R. Morris, and Diana E. Pedraza2020
Scientific Investigations Map 3461Pamphlet accompanies map
U.S. Department of the InteriorU.S. Geological Survey
I SBN 978- 1- 4113-4377- 1
9 7 8 1 4 1 1 3 4 3 7 7 1
