Glen Rose Formation
Nomenclature. —This formation, the Caprotina limestone of Shumard (1463, pp. 583, 588), was first named Glen Rose by Hill (772, pp. 504-507) in 1891. The type locality is in the thinned shoreward extension of the formation along the Paluxy River near Glen Rose, Somervell County.
Stratigraphic position and contacts. —Basally, it is in gradational contact with the Travis Peak sands. It is absent west and north of the line shown in Fig. 16. North of about the latitude of Waco, it is overlain, probably in gradational contact, by the Paluxy sands, which Scott claims to be littoral deposition in a withdrawing sea at the end of Trinity time. Hill had previously indicated that the Paluxy is a sandy phase of the upper Glen Rose limestone.
Facies. —The Glen Rose is a calcareous formation, in part clayey and sandy, and is of the neritic facies. As already explained, it is 29This name—has priority over the Sycamore limestone in Oklahoma (J. A. Taff, 1903) . Hill, 742, 753, 762, 767, 780, 783, 795, 803, 827; Rauff, 1286; Scott, 1394; Udden, 1623; Vanderpool, 1678, 1679, 1681a; Cooperative maps, Parker and Wise counties, 1853. replaced she-rewards by sand. Numerous features, ripple marks, dinosaur tracks, plants, gypsum, and general lithology, indicate that at many places it was deposited in shallow water.
Areal outcrop, local sections. —The Dierks and De Queen limestone lentils in southwestern Arkansas contain Ostrea franklini, Anomia texana, Modiola branneri, Eriphyla pikensis, Glauconia branneri and other Trinity fossils. Outfingerings of similar limestone outcrop in western Parker County, Texas, where the marginal Glen Rose contains three zones (1394, p. 41) : (1) near the base, a zone characterized by Orbitolina texana (Roemer), Porocystis globularis (Giebel), Pecten stantoni Hilland Trigonia stolleyi Hill; (2) near the middle of the formation, a zone of abundant Orbitolina texana, and some Loriolia texana (Clark) ; and at the top, a mass of Modiola branneri and some Porocystis n. sp. (elongated) . Just above the second zone is a Monopleura-Toucasia bank. In this section at least three limy outfingerings of the Glen Rose into the Paluxy facies are mappable. A similar situation is seen on subsurface profiles in Denton County, where several such limy outfingerings occur (Fig. 17).
The Glen Rose typically consists of thin- to medium-bedded hard continuous limestone strata alternating with marl or marly limestone, and weathering in stream cuts to steep canyons and on hillsides to a terraced or "staircase" topography. The narrow Glen Rose prairie passes from Mt. Bonnell northwest of Austin to near Burnet, and thence northwards to west of Lampasas, up the large scarp east of Pecan Bayou in Mills and eastern Brown County to near May, thence northeastwards to make a large southeast reentrant down Leon River in northern Comanche County, thence northwards to near Desdemona, and northeastward to the Brazos in southwestern Parker County. Its last limy outfingerings occur near Decatur and elsewhere in Wise County. Inits outcrop south of the Brazos, it gradually increases in thickness to about 720—800 feet near Waco. In Bell County, the 500-664 feet of Glen Rose consists of pure, solid limestone near the middle, thinner bedded, shalier, and sandier limestones near the base and the top, and two general water horizons, located respectively 130-175 and 240 feet below the top. In the Faleozoic inlier at Lampasas (1574, pp. 329—338), following about 20 feet of basal heterogeneous conglomerate and 30 feet of yellowish, brown, and whitish packsand, sandstone, and grit, there is about SO feet of Glen Rose limestone, sandy and transitional in lithology at the base, and more calcareous above. It consists of soft, impure limestone, alternating with marly lime and soft yellow sandstone, the strata being thin-bedded and well stratified. From Twin Sisters Peak, to Bachelor Peak 18 miles to the southeast, it has increased in thickness from 90 to 200 feet.
The McAngus well near Elroy, eastern Travis County had in excess of 1066 feet of Glen Rose (1854-2920), and more than 180 feet of Travis Peak (2920-3100 T.D.). The city of Austin Blunn Creek well in Travis Heights had 800+ feet of Glen Rose (825?- 1632), and 558 feet of Travis Peak (1632-2190).
Celestite occurs in pockets at a level near the top of the Glen Rose at many places in central Texas: on Donaldson Creek due east of Nix,in the escarpment north of Nix, in Rocky and South Rocky creeks near Lampasas, South San Gabriel diver north of Leander, Mount Bonnell north of Austin, and elsewhere. Anhydrite is recorded in Comanche, Lampasas, and western Parker counties (803, p. 146). In the Hubbard city well, Hill County, a 30-foot layer of anhydrite occurs near the depth of 2855 feet. Anhydrite occurs in the Glen Rose in Arkansas, Louisiana, and Maverick County, Texas.
West of Austin the Glen Rose shows the same gulfward thickening and change of facies. At Fredericksburg (795, pp. 221, 314) it is about 55 feet thick, and at Kerrville about 600 feet thick. A similar change southwards occurs across Sutton, Edwards, and Kinney counties. For Glen Rose in Trans-Pecos Texas see pages 292-297.
Paleontology. —In the central Texas outcrop counties, where it has been most studied, the Glen Rose is from 400 to 800 feet thick, but underground in the Gulf Coastal Plain, it exceeds 3500 feet. Its fossil zonation is nowhere known, and it is probable that the reduced outcrop thickness represents only the upper portion of the complete formation. If so, all existing fossil partitions are very defective. Pending fuller study of thick subsurface sections, such as those in Maverick County and Louisiana, or thick outcrop sections, such as those in northern Mexico and the southern Quitmans, no general zonation for the formation can be outlined.
The Quitman section contains, associated with or slightly above Malone fossils, a prominent zone of Exogyra quitmanensis Cragin. This, or a similar oyster, occurs at the base of the section in the rim and in Glen Rose inliers in the Solitario. Associated fossils are Trigonia, a large Pecten n. sp., Alectryonia aff. carinata and echinoids like Toxaster. Several hundred feet above this are the main Orbitolina texana zones. The succession of zones in the Quitmans and the Solitario is as follows:
Exogyra texana (abundant) -Walnut Orbitolina texana, and Glen Rose echinoids Glen Rose, Bluff bed Douvilleiceras, Parahoplites and other ammonites Basal Glen Rose Exogyra quitmanensis Quitman bed; Cuchillo Trigonia taffi Basal Quitman; Cuchillo Fossils unknown Mountain bed; Las Vigas Malone fossils : Torcer
In central Texas, several zones of Orbitolina texana and other allied foraminifera have long been known; some ammonites (Douvilleiceras, Parahoplites and Dufrenoya) occur but have not been worked out; and a large smooth Exogyra resembling that from the Solitario occurs.
A Douvilleiceras n. sp., with depressed cross-section and reduced tubercles, was blown out of Dixie Dillon No. 43 well, Pine Island, Louisiana, from below the casing, at 3338 feet. It is from the lower Glen Rose limestone, above the 2000 feet of red shale.
Vanderpool (1678, 1679) lists the following ostracoda from the Trinity group in southern Arkansas, northwest Louisiana, and near Weatherford, Texas: Bairdia dorsoventrus Vanderpool Cypridea sp. indet. Bairdia glenrosensis Vanderpool Cytheridea trinitensis Vanderpool Bythocypris rotundus Vanderpool Cythere ornata Vanderpool Cypridea diminutus Vanderpool Paracypris weatherfordensis Vander- Cypridea tuberculata Sowerby var. pool gypsumensis Vanderpool Pontocypris perforata Vanderpool Cypridea ventrosa Jones var. bispinosus Vanderpool
Algal (Chara) oogonia occur in many widely separated areas in the Trinity group in the Southwest. They have been reported from the De Queen limestone member of the Glen Rose in Arkansas (1678, p. 98), from the Glen Rose in northern Texas (1791, p. 64), from the Glen Rose in the Kokernot well near Hovey (633), and from strata referred to the Trinity in various wells in the Fort Stockton district (12, pp. 33—37). Chora oogonia appear to be more prevalent on the southern edge of the Salt basin and along the Fort Stockton-Yates high area. They occur in the Perm Alvis well about 2 miles south of Belding; the Lockhart Webb well west of Fort Stockton; in various wells along the southern flank of the Fort Stockton high; crest of Yates Pool; Riley Murphy well, west of Sheffield; Cosden Perner well, Crockett County; and well in central Irion County. Some Chara are found in a greenish-gray shale with limestone concretions, gypsum and ostracoda, which underlies the "Basement sand" (Maxon, Paluxy?). These basal shales are 100 or more feet thick near Fort Stockton, about 250 feet thick at Yates, and near 600 feet thick at Belding.
Wieland (1758a, 1759, 1759a) records the following Trinity cycads :
Cycadeoidea boeseana Wieland (Basal Trinity sand; near Bridgeport) Cycadeoidea barti Wieland (Paluxy, near Comanche; Gillespie sand, near Fredericksburg) Cycadeoidea wolfei Wieland (Paluxy, near Stephenville) Cycadeoidea dyeri Wieland (Paluxy; near Tolar and Stephenville) Cycadeoidea johnstoni Wieland (Paluxy, near Stephenville) Wieland says: "The Trinity beds must be ranked as one of the five great cycad-yielding terranes of North America—the other four being the Arundel of Maryland, the Lakota of the Black Hills region, the Como of the Black and Freeze Out Hills, and the Mesaverde of the Chuska Mountain region of New Mexico and Arizona ... The Trinity was a flat, subsident, river and bayou, cycad-dinosaur-conifer, forest land, swept by the shallow edges of the sea." Jones (888, p. 770) says: "The writer has seen nodules of pure coal imbedded in the Glenrose limestones of Bandera County, Texas."
The foraminifera from the Glen Rose have not been carefully studied, but probably Orbitolina-like forms of two or more genera exist. The corals show a great variety, some being reef -forming. Forty or more species have been collected and are being described by Mr. J. W. Wells (1727). The mollusca in the outcrop counties show a great variety; only a few have been described by Hill, Conrad, and others. The alleged bryozoan genus Porocystis marks the Glen Rose. Echinoids are abundant and as yet undescribed.
The most distinctive Glen Rose foraminiferal genus is Orbitolina, of which a common species, O. texana, was described by F. Roemer in 1849. The genus has been recently reviewed by Vaughan (1688a). He considers the 320 The University of Texas Bulletin No. 3232 larger O. whitneyi Carsey to be only a large-sized variant of 0. texana, and 0. texana asaguana Hodson and 0. texana monagasa Hodson (from Venezuela) to be only growth forms of 0. texana. He says (1688a, p. 610) :"0. walnutensis Carsey [from the Fredericksburg group] differs so greatly from the other species that it may belong to another genus"; Silvestri (1479a) has referred it to Dictyoconus.
Glen Rose corals (Wells, 1727, 1727 a) occur largely in reefs, located in the lower half of the formation, and built on great masses or layers of caprinids. The lowest reef, at the base of the Glen Rose in Hays, Comal, and Blanco counties, has afforded 6 species of Isastrea, Orbicella, Astrocoenia, and other genera, and has a height of 3 to 10 feet over an area of several square miles. Reefs located about 100 feet above the basal reefs are 15 to 30 feet thick, and contain numerous types of corals, some brachiopods. oysters, and other fossils. A third coral horizon occurs about 200 feet above the base of the Glen Rose.
Dinosaurs, mostly tracks, are known from the following localities: Kinney County near northeast corner on the Edwards ranch; northeastern Uvalde County near Utopia on the Loman ranch; southeast corner of Kimble County on the Garner ranch, about 7 miles west of Kerrville and 13 miles north of the Kerrville-Junction road; southern Bandera County, in Hondo Creek. 2 miles downstream, and 2% to 3 miles upstream, from Tarpley; Medina County, Hondo Creek, about 13 miles northwest of Hondo; Travis County (reported), about 15 miles up Colorado River from Austin; near Glen Rose, Somervell County (1452) ;in Hamilton County (1805). Bones, said to be of a Morrison dinosaur Elaps, were found by Darton (N. H. Darton, oral communication) in the Middle Concho River in eastern Irion County, probably in Paluxy sand. Wieland (1759a) records a nearly complete dinosaur skeleton from the Paluxy?, on Paluxy River near Stephenville. Gould (626) records a dinosaur from the Antlers sand in southern Oklahoma.
Plants have been described (545) from the Glen Rose near the type locality.