Devils River Research Articles

Physical Stratigraphy and Facies Analysis, Lower Cretaceous, Maverick Basin and Devils River Trend, Uvalde and Real Counties, Texas: ABSTRACT

The formations of the Fredericksburg and lower Washita Groups in Uvalde and Real Counties, Texas, were deposited on a broad platform behind the Stuart City reef trend. Nine distinct lithofacies and corresponding depositional environments occur within this lower Cretaceous depositional regime: (1) nodular and burrowed mollusk lime wackestone lithofacies representing an open-marine platform, low wave-energy environment; (2) rudist, shell fragment, miliolid wackestone to packstone lithofacies representing a partially restricted to open-marine platform, low to moderate wave- and current-energy environment; (3) rudist, shell fragment, miliolid, grainstone to wackestone lithofacies representing an open-marine platform and bank, moderate to high wave- and current-energy environm nt; (4) evaporite collapse breccia lithofacies representing a hypersaline platform interior environment; (5) miliolid, shell fragment wackestone and Texigryphaea bed lithofacies representing a platform interior, shallow subtidal to intertidal transitional environment; (6) alternating thin evaporite collapse breccia with laminated mudstone and pellet packstone lithofacies representing an evaporite-dominated tidal mud flat environment; (7) carbonaceous lime mudstone lithofacies representing a platform interior euxenic lagoonal environment; (8) pellet intraclast lime wackestone to packstone lithofacies representing a restricted platform interior environment; and (9) pelagic lime mudstone to wackestone lithofacies representing a deep, open to slightly restricted platform interior environment The Fredericksburg-early Washita depositional history is characterized by 2 distinct cycles of deposition. The first cycle is interpreted as an initial marine transgression over the partially eroded Glen Rose tidal flat deposits, followed by a period of regional shoaling, culminating with the deposition of the Kirschberg Evaporite within the Devils River formation and northward, and deposition of the lower McKnight evaporite-dominated tidal mud flat sediments to the south. The second cycle of deposition is interpreted as a gradual marine transgression culminating in the deposition of open-marine platform rudist bank facies (upper Devils River) and partially restricted to open deep platform interior deposits (Salmon Peak) prior to middle Washita emergence and erosion forming the pre-De Rio unconformity. End_of_Article - Last_Page 508------------

Relict caves as evidence of landscape and aquifer evolution in a deeply dissected carbonate terrain: Southwest Edwards Plateau, Texas, U.S.A.

Caves lying well above valley floors and within narrow ridges of carbonate rocks in the deeply dissected southwest Edwards Plateau, Texas, provide considerable information about the geomorphic history of the region and the evolution of the Edwards-Trinity aquifer. In the Sonora area, horizontally extensive cave passages occur at three distinct levels along massive burrowed dolomitic beds in the Cretaceous Segovia Formation. Passages lying beneath a resistant caprock consist of long corridors, barren of speleothems. However, in the vicinity of the caprock edge, passages are modified by collapse and stoping, mazework, and speleothem deposition. Conduits are generally oriented down the regional dip and guided by dominant NE-trending fractures. Upper cave levels developed first, but lower passages were excavated as piezometric surfaces dropped in response to valley cutting. Cavern collapses blocked flowpaths in places and ensuing floodwaters enlarged passages, formed maze sections, and promoted development of diversion routes around these constrictions. Collapse at the caprock edge has enhanced retreat of valley slopes and headward erosion of streams. In the Langtry area, caves developed in the Cretaceous Devils River Formation are up to 113 m deep. The Devils River Formation is a stratigraphically-homogeneous high-purity limestone, in which fractures are few but vertically extensive. Incision of the Rio Grande and nearby streams has locally exposed up to 70 m of the Devils River Formation, inducing steep hydraulic gradients that have promoted bathyphreatic circulation and development of deep cave systems. Horizontal passages are relatively short and are connected by vertical shafts and steeply inclined corridors. The two localities have experienced similar climates and dissection in topography, but the relationship of stream incision to geologic structure, stratigraphy and lithology has differed significantly enough to produce long horizontal caves within the shallow phreatic zone around Sonora and deep vertical caves in the deep phreatic zone around Langtry.

Species Composition and Diversity of Benthic Macroinvertebrates of Lower Devil's River, Texas

Species Composition and Diversity of Benthic Macroinvertebrates of Lower Devil's River, Texas

Rediscovery, Distribution, and Populational Status of Cyprinodon eximius (Cyprinodontidae) in Devil's River, Texas

Rediscovery, Distribution, and Populational Status of Cyprinodon eximius (Cyprinodontidae) in Devil's River, Texas

Structural Analysis of Devils River Uplift-Southern Val Verde Basin, Southwest Texas

Surface and subsurface structural geologic investigation has defined several major structural trends in parts of Edwards, Kinney, and Val Verde Counties, Texas. Seven rock units of the Cretaceous Comanche Series and two rock units of the Cretaceous Gulf Series crop out in the study area, part of the southwest Edwards Plateau physiographic province. Surface strata have a regional dip of ½ to 2° SW, interrupted locally by zones of faulting and/or folding that generally overlie larger scale late Paleozoic structural features. The east-west-trending Carta Valley fault zone, which crosses central Val Verde and southwest Edwards Counties, is marked by a pattern of en echelon folds and faults that bound a series of graben blocks. The deformational style of this zone su gests left-lateral wrench faulting in basement rocks. Two other surface fault zones that displace Cretaceous rocks are less well developed but also appear to overlie basement faults. A distinctive monocline trends northwest-southeast from east Val Verde through northwest Kinney Counties, approaching parallelism with the Balcones fault zone in the southeastern part. This flexure, the Sycamore Creek monocline, has exhibited positive tendencies since middle Cretaceous time. A poorly expressed southwest-plunging anticline marks the crest of the Devils River uplift in southeast Val Verde County. Parts of three major late Paleozoic tectonic features are present in the subsurface--the southeast Val Verde basin, the Devils River uplift, and the north edge of the Ouachita thrust belt. A foreland sequence of lower to middle Paleozoic carbonate shelf deposits, overlain by thick upper Paleozoic clastic sedimentary rocks, fills the Val Verde basin. The Devils River uplift, the elevated southern margin of the Paleozoic Texas craton, marks the southern limit of the Permian Basin depositional province. Weakly metamorphosed deep-water sediments of the Ouachita interior zone are thrust northward over a Cambrian-Ordovician sequence on the uplift. Subsurface mapping shows that a major down-to-the-north late Paleozoic fault, which separates the Val Verde basin from the Devils River uplift, underlies the surface Carta Valley fault zone. Transcurrent movement may have occurred along this fault during the Ouachita orogeny as a result of plate convergence. The axis of the Sycamore Creek monocline also lies above basement faults along which relatively minor up-to-the-north displacement occurred during Cretaceous and Cenozoic time, a reversal of major late Paleozoic movement. In general, thorough analysis of subtly expressed surface structural features has proved a valuable guide to mapping and interpreting the more pronounced Paleozoic structures beneath the pre-Cretaceous unconformity.

Lower Palaeozoic rocks of New Zealand

Abstract Lower Palaeozoic rocks of New Zealand are confined to the West Nelson-Westland Region and Fiordland Region. Fiordland rocks are largely intermediate to high-grade metamorphics, and New Zealand's early Palaeozoic stratigraphy is established on the sequence of West Nelson and Westland. Within West Nelson and Westland, Lower Palaeozoic strata form three main belts — the Western, Central, and Eastern Sedimentary Belts, separated by major faults, the Anatoki Thrust and Devil River Fault. The lithostratigraphic succession of each belt is outlined. The Western Sedimentary Belt is composed of a quartz-rich sequence of sandstone and mudstone, largely of turbidite origin, and graptolitic black shale; age range is Late Cambrian (or earlier) to Late Ordovician. In contrast, the Central Sedimentary Belt is characterised by volcanics, volcanogenic sediments and carbonates and ranges from Vendian or Early Cambrian to Late Ordovician in age. The Eastern Sedimentary Belt is composed of carbonates followed by quartz-rich clastics and is of Early Ordovician to Early Devonian age. The sediments are thought to represent a western non-volcanic flysch trough (or prism) assemblage and an eastern volcanic arc-carbonate assemblage, brought into juxtaposition by thrust faulting during or prior to the earliest Devonian. A western, continental, source area is inferred for the non-volcanic trough assemblage whereas sediments in the volcanic arc assemblage are largely authigenic or are derived from older units of the same assemblage. Fossils represent the Vendian, Middle and Upper Cambrian, Lower to Upper Ordovician, Middle to Upper Silurian, and Lower Devonian. A relatively complete graptolite succession in Ordovician rocks has enabled recognition of 11 graptolite zones. The zones are correlated with those of Victoria, Australia, and the Victorian stages are used for the New Zealand sequence. Faunal affinities lie most closely with faunas of Australia. A major volcanic episode in the Middle and ?Early Cambrian is represented by a thick pile of basic to intermediate volcanics and volcanogenic sediments (Devil River Volcanics) in the Central Sedimentary Belt. Volcanism continued sporadically in the Upper Cambrian and lower Lower Ordovician. A small ultramafic body of peridotite, orthopyroxenite, websterite, and gabbro was emplaced within Devil River Volcanics in the? Lower or Middle Cambrian. Widespread granites of the Tuhua and Karamea belts appear to be largely of Middle Devonian or younger age. Many mineral ages in these rocks have been reset by a major thermal event associated with further granite emplacement in the mid Cretaceous. Rocks of all three belts have suffered polyphase deformation, and structure is complex. An early phase of recumbent folding (F1) is recognised in the Central Sedimentary Belt and has been strongly overprinted by north-south trending tight folds (F2) with steeply-east-dipping axial planes. Faulting is severe, particularly in the Central Sedimentary Belt where thrust faulting and nappe formation has been recognised. At least four deformational events can be recognised; the Haupiri Disturbance (late Middle to Early Cambrian), the Greenland Event (late Ordovician to Silurian), the “sub-Baton” event (early Early Devonian), and the main phase of the “Tuhua Orogeny” (Middle to Late Devonian). The problem of regional structure is discussed within the context of two alternative models. The sedimentary, igneous and metamorphic-tectonic history of the Fiordland Region is poorly known. The most recent work suggests a. basement complex of retrograded granulite facies rocks overthrust by a metasedimentary cover sequence (possibly including equivalents of the West Nelson-Westland formations) and now metamorphosed to amphibolite facies. Sparse isotopic age data suggest a Devonian age for the amphibolite facies metamorphism.

Evidence for Wrench Faulting, Southern Val Verde Basin, Southwest Texas: ABSTRACT

A structural analysis in the southwest Edwards Plateau area included four 15-minute quadrangles in Edwards, Kinney, and Val Verde Counties, Texas. Seven rock units of the Cretaceous Comanche Series and two units of the Cretaceous Gulf Series crop out. Subsurface Paleozoic foreland facies rocks of the southern Val Verde basin are present in the northern study area; the Devils River uplift, partly blanketed by allochthonous upper Paleozoic metamorphic rocks, underlies the southern part. A pronounced east-west-trending fault zone which cuts through the center of the study area is at least 55 mi (88 km) long and 1 to 2 mi (1.6 to 3.2 km) wide. This trend, named the Carta Valley fault zone, is characterized by a complex series of en echelon, northeast-oriented faults which are cross-cut by a lesser number of northwest-trending faults. These faults bound a series of grabens, downthrown by 200 to 300 ft (60 to 91 m), which are as large as 3 sq mi (7.7 sq km). Nine gently dipping, northwest-plunging, en echelon anticlines parallel the south side of the fault zone. The configuration End_Page 1428------------------------------ of faults and folds strongly suggests that the surface fault zone formed by left-lateral wrench displacement in the basement rocks. Subsurface data show that the fault zone overlies a major late Paleozoic high-angle fault, downthrown to the north by over 10,000 ft (3,050 m), which marks the Devils River uplift-Val Verde basin boundary. The surface fault zone may thus be a later reflection of more pronounced wrench faulting along this basement fault during the Ouachita orogeny. End_of_Article - Last_Page 1429------------

Response of the Devil's River (Texas) Fish Community to Flooding

Flooding on the Devil's River, Texas, caused changes in both physical and biological structure of the river. Habitat types became less distinct and generally more riffle-like. Fish species diversity, evenness and number of species decreased. Higher diversities were expressed nearer the river's terminus, indicating flood-resistance there. Prior to the flood 18 species associations existed; 13 existed after flooding, only three of which were present prior to flooding. Six species dominated both preand post-flood community biomass and maintained the same rank-order dominance in both flood regimes. These (Dionda episcopa, Notropis proserpinus, N. amabilis, Astyanax mexicanus, Notropis venustus and Dionda diaboli) occupied slightly different habitats or utilized different resources of the same habitat in the post-flood regime. All are adapted to a flood-prone environment and may constitute the greatest degree of faunal stability in the ecosystem.

Subsurface Positive Elements within Ouachita Foldbelt in Texas and Their Relation to Paleozoic Cratonic Margin

Two major subsurface positive elements within and marginal to the Ouachita foldbelt in Texas, south and east of the foredeep basins, have been defined by recent drilling and seismic data. Uplifted foreland carbonate rocks of early Paleozoic age were drilled on the Devils River uplift in southwest Texas in Shell 1 Stewart. This structure is interpreted to be a differentially uplifted autochthonous basement block partly overridden by the interior zone of the Ouachita foldbelt. The presence of a second major linear positive element has been established in east-central Texas by seismic records and by Shell 1 Barrett. A faulted anticlinal structure, herein named the is at least 25 mi behind the leading edge of overthrust Ouachita facies rocks. A massive section of intensely deformed foreland carbonate rocks of early and middle(?) Paleozoic age, overlain by allochthonous low-grade metaclastic rocks of Ouachita facies, was drilled in the Barrett well. The uplift appears to be similar in structural position and history to the Devils River uplift, but the Waco uplift is probably a parautochthonous block which was partly involved in late Paleozoic orogenic thrusting. The Waco and Devils River uplifts are subregional elements superimposed on a broad elongate gravity maximum which can be traced from the Ouachita Mountains to near the Marathon area. This maximum, thought to be the result of uplift of the dense mafic crustal layer, may have marked the edge of the early and middle Paleozoic (preorogenic) continent. A well-defined, persistent, depositional and tectonic boundary between the constructional carbonate miogeocline and thinner contemporaneous pelitic deposits of the geosyncline was also apparently localized along or near the periphery of this inferred crustal margin. Therefore, the two uplifts are interpreted to be external massifs in structural and stratigraphic positions similar to those of the Green Mountains-Blue Ridge chain of basement u lifts in the Appalachians. Isotopic dates from both Ouachita facies and foreland rocks of the cratonic margin record multiple Paleozoic thermal events and probable accompanying deformation along the tectonic belt. The data also confirm the ancestral middle, and possibly early, Paleozoic origin of the Devils River and Waco uplifts. The presence of a post-Precambrian, pre-Late Cambrian volcanic and metasedimentary province in the area of the Devils River uplift is suggested by Rb-Sr dating of rocks drilled in the 1 Stewart well. Foreland strata in the 1 Stewart are essentially undeformed, but the rocks in the 1 Barrett are metamorphosed to greenschist facies and highly contorted and sheared. Some formation fluids and minor hydrocarbon shows were recovered from these tests, but the quality of the reservoirs was generally poor.

Stratigraphic Revision, Edwards Group (Lower Cretaceous) of Texas, and Regional Surface-Subsurface Synthesis: ABSTRACT

Porous carbonate rocks called form a widespread aquifer in the Edwards Plateau region of west-central Texas and prolific petroleum reservoirs beneath the coastal plain of south-central Texas. Recently completed surface mapping in the Edwards Plateau and subsurface mapping in south-central Texas permit correlation of Edwards rocks in both areas, and allows the entire central Texas region to be viewed as an evolving carbonate depositional complex. To better express this surface-subsurface synthesis, a new stratigraphic nomenclature is proposed: Edwards is elevated to group status, 2 new outcropping formations are recognized in the Edwards Plateau, and 2 new formations are defined in the subsurface of south-central Texas. Previously unverified disconformities at an near the top of the Edwards have been documented and a boundary that was considered to be disconformable is now interpreted to be conformable. Regional structural-depositional elements that influenced Edwards deposition are reflected by lithofacies and isopach patterns. Dominant elements on the Comanche shelf formed a vast sediment trap in which shallow marine and tidal flat carbonates and evaporites accumulated preferentially over the Central Texas platform, protected by the Stuart City reef on the southeast, the Devils River bank on the southwest, and the broad North Texas shelf-lagoon on the northwest and northeast. Edwards and associated rocks record the progressive inundation of the Central Texas platform. Porosity in the subsurface Edwards is related chiefly to early exposure on positive tectonic elements, whereas porosity in the surface and near-surface Edwards is related chiefly to the present geomorphic cycle. End_of_Article - Last_Page 361------------

Positive Elements Within Ouachita Tectonic Belt in Texas: ABSTRACT

Two major positive elements south and east of the foreland basins marginal to the Ouachita tectonic belt in Texas have been confirmed by wells drilled by Shell Oil Company and by seismic data in and adjacent to the concealed structural belt. Foreland facies sediments (dominantly carbonates) of early and possibly middle Paleozoic age were drilled on the Devils River uplift in southwest Texas. In addition, much of the Devils River uplift is apparently underlain by a Precambrian intrabasement basaltic flow(?) which has been mapped from seismic reflections and penetrated in Shell No. 1 Stewart. The presence of a second major linear positive element covered by lower Paleozoic foreland rocks has been established in east-central Texas by seismic records and by Shell No. 1 Barrett. This faulted anticlinorial structure, herein named the Navarro uplift, is at least 25 mi behind the leading edge of overthrust Ouachita facies rocks. It appears to be similar in structural position and history to the Devils River uplift but the data are insufficient to determine definitely the structural style of either. Foreland strata are metamorphosed to greenschist facies. Some formation fluids and minor hydrocarbon shows were recovered but the quality of the reservoir was generally poor. The carbonates on the Navarro uplift contain extensive shear and flowage structures and resemble the marbles in wells on the south flank of the Devils River uplift. Isotopic age dates from both Ouachita facies and foreland rocks record multiple Paleozoic thermal events and probable accompanying deformation along the tectonic belt. The isotopic data also suggest the presence of a post-Precambrian, pre-Late Cambrian volcanic and metasedimentary province in the area of the Devils River uplift. End_of_Article - Last_Page 362------------

A new subgenus of intranasal chiggers of the genus Microtrombicula from North America and Korea.

Crypticula, new subgenus, type species Trombicula merrihewi Loomis & Lipovsky, is proposed in the genus Microtrombicula Ewing. Microtrombicula (Crypticula) diabola, n. sp., from is Devils River, Val Verde Co., Texas, from nasal passages of Peromyscus difficilis. Other species included in the subgenus are Trombicula ornata Loomis & Lipovsky, Microtrombicula nasalis Loomis and M. wrenni Loomis from North American cricetid rodents; M. kyongkiensis Ah, M. loomisi Ah, M. miniopteri Ah, and M. pipistrelli Ah from Korean bats.

Oil-Impregnated Sandstones Between Dirty Devil and Colorado and Green Rivers, Garfield and Wayne Counties, Utah: ABSTRACT

Oil-impregnated sandstone has been known in Elaterite basin, Wayne County, Utah, since the early 1900s. Subsurface information and recent field work show these deposits to be more extensive than formerly recognized. Genetically related deposits occur in a triangular area bounded by the Green and Colorado Rivers on the east, the Dirty Devil River on the west, and a poorly defined line on the north, an area called here the sand triangle. Major deposits occur in the White Rim Sandstone Member of the Cutler Formation (Permian). Less important deposits, generally in close association, are in the Organ Rock and Cedar Mesa Members of the Cutler (below the White Rim Member), and in the basal part of the Triassic Moenkopi Formation (above). Oil in the major surface deposit, Elaterite basin, accumulated in a north- to southwest-trending, arcuate, offshore bar which developed along the northwest and west flank of the mildly positive Monument upwarp during small transgressions and regressions of the shallow Permo-Triassic sea. The Elaterite basin bar formed on a shoal caused by the presence of a gently dipping, local anticline. Erosion of the Colorado River and tributaries during late Tertiary time has breached this large stratigraphic trap, permitting volatile hydrocarbons to dissipate. Included in the complex of bar deposits are (from north to south): Elaterite Basin, Red Cove (new name), Teapot Rock, Tar Cliff, Fault Point, and The Cove. At one time these bars formed a single, complex oil field which now is broken up by rosion. Oil impregnation ranges from very slight to fully saturated (with active seeps) in an area 22 mi long and 1.5 mi wide. Maximum thicknesses are 250 ft. Reserves observable at the outcrop exceed 1 billion bbl of 8°-15° API oil. Undoubted continuity of deposits beneath the surface makes it possible to estimate reserves of 3 to 4 billion bbl. Smaller deposits also occur downdip on the west in similar stratigraphic traps in the upper White Rim-basal Moenkopi interval. Wells west of the outcrop have penetrated oil-impregnated beds as thick as 200 ft; these occurrences probably are in similar offshore bars which parallel the Elaterite Bar system and the White Rim-Moenkopi strandline. Oil-impregnated sandstone may be present beneath an area of 100 to 140 sq mi. End_of_Article - Last_Page 218------------

Stratigraphy of Edwards and Associated Formations, West-Central Texas: ABSTRACT

West-central Texas is strategically located along the Texas Comanche outcrop belt. On the east and north, the Comanche section is influenced by terrigenous End_Page 2166------------------------------ clastics allowing the classic formational breakdown of this region. On the south and west, the section is almost entirely limestone. The area of study is a convenient avenue for correlation between these two areas. The Cretaceous of west-central Texas consists of a basal quartz sand, the Antlers Sand, and an overlying carbonate sequence. The Antlers is laterally equivalent to both Fredericksburg and Trinity sequences at the northeast. The southern limit of the usefulness of the term is at the latitude of the Brady Mountains, Menard County. The carbonate sequence above the Antlers can be divided into two geologically distinct areas; a northern area, generally coincident with the Callahan Divide, and a southern area underlain by the northern Plateau. The carbonate sequence on the Callahan Divide may be broken into two units: (1) a basal, nodular, marly unit, and (2) an overlying massive, rudistid-bearing limestone. The basal unit has characteristics of, and is laterally equivalent to, the Walnut and Comanche Peak Formations of central Texas. These units cannot be recognized and the sequence is termed the Walnut-Comanche Peak undifferentiated. The overlying massive rudistid-bearing limestone is continuous with the of north-central Texas and the term is used across the Callahan Divide. South of the northern Plateau, the Limestone replaces the Walnut-Comanche Peak by facies change to occupy the entire Fredericksburg interval. The term Edwards should include the beds which extend southward into the Plateau proper until they are lost at the position of the Devils River Limestone in and Val Verde Counties. The top of the is an unconformity from and Val Verde Counties northward to an east-west line running through central Irion, Tom Green, and Concho Counties. North of this line the contact appears to be conformable. The base of the unit lying above the (unnamed upper formation of Lozo and Smith) is termed the Dr. Burt ammonite beds. This stratigraphic datum can be extended northward from the Plateau to he Callahan Divide south of Abilene in Nolan County. End_of_Article - Last_Page 2167------------

Patterns of Social Behavior of Merriam's Canyon Lizard (Sceloporus M. merriami-Iguanidae)

The social behavior of a group of 19 canyon lizards, Sceloporus merriami, was observed in a large enclosure. The pattern of movements and the cadence of these movements in the display sequence are species-specific. The domi- nant male is responsible for the majority of aggressive actions such as displaying, courting, fighting, and chasing in the group. Subordination is indicated by retreat, submission and reduced activity. Dominance was shared by two males, and when they were removed a new dominant male arose and maintained his dominance when the previous dominants were returned. A courting male nods rapidly while follow- ing a female and attempts to get a biting grip on the skin of her shoulder region to effect copulation. One observation suggests that the female may sometimes initiate courtship and mating. The canyon lizards observed in this study were captured in early April, 1960, along the canyon walls of the Devils River, 10 miles north- west of Del Rio, Val Verde County, Texas. They were kept in cages until early June and then released in an outdoor enclosure at the University of Oklahoma Biological Station in south-central Oklahoma. The square enclosure of galvanized sheet metal measured 10 feet on a side and was 3 feet high. The enclosed area contained fine sand vary- ing in depth from two inches near the sides to a one foot dune in the center. A row of six cinderblocks was stacked three, two, one along the top of the dune while stacks of two only were placed near three corners. A six foot by three inch pole was erected near one side and small pieces of wood were scattered over the area. Water was provided in a large sunken clay dish. Insect food was provided daily from sweep nettings. Other lizard species present in the enclosure included Scelo- porus woodi, Sceloporus graciosus, Sceloporus scalaris, Uta stansburi- ana, Urosaurus ornatus and Urosaurus graciosus. All individuals were color marked for individual recognition. Re- cording methods included still and movie photography and tape re- cordings. Observation periods were from 8:00 a.m. to 11:00 a.m. and 4:00 p.m. to 6:00 p.m., when the lizards were most active. Observa- tions began on June 10, when 19 canyon lizards (9 females, 10 male) were released into the enclosure, and continued on 25 different days until July 28 when observations were terminated.

Gambusia senilis from the Devil's River, Texas, an Addition to the Fish Fauna of the United States

Gambusia senilis from the Devil's River, Texas, an Addition to the Fish Fauna of the United States

Nummoloculina in Lower Cretaceous of Texas and Louisiana

Several occurrences of the miliolid Nummoloculina in the Lower Cretaceous of Texas (lower Glen Rose through upper Devils River limestones) and one occurrence in the Lower Cretaceous of northern Louisiana (lower Glen Rose limestone) are reported for the first time. The geologic range of Nummoloculina as ascertained by the writers is Lower Cretaceous to Recent. Nummoloculina limestones in Texas are here reported from the upper Devils River limestone (Georgetown limestone equivalent) in Val Verde County and the Edwards limestone in La Salle and Maverick counties. Nummoloculina occurring in the Devils River limestone in Val Verde County is figured and discussed. Nummoloculina from the El Abra miliolid member of the El Abra formation of northern Mexico (Lower Albian through Lower Cenomanian) is figured for comparison. The uppermost Devils River limestone and the upper El Abra miliolid member are compared, but no correlation is implied. Following Norton's zonation of foraminifers, miliolid limestone environments would correspond most closely with his Zone A where the water is 0-5 fathoms deep and the temperature is 21°-32°C. Miliolids occurring in abundance are facies foraminifers characteristic of back-reef and inter-reef environments; therefore, they are useful in paleoecology. Although miliolid limestones in Texas vary in age within, but are restricted to the Lower Cretaceous (Sligo through upper Devils River limestones), they may be of local or regional value in the differentiation of large stratigraphic units within the Sligo through upper Devils River limestones. Miliolid limestones are used successfully in parts of southwest and central Texas to mark the faunal top of the Edwards limestone. However, in the Devils River area, or in any other area where reefs were formed in Washita as well as Fredericksburg limestones, such differentiation based on miliolids is unsatisfactory.

GEOLOGY OF AGUA FRIA QUADRANGLE, BREWSTER COUNTY, TEXAS

The 15-minute Agua Fria quadrangle in southwestern Brewster County, Texas, is arid, sparsely vegetated, and includes diverse topographic features that result chiefly from complex structure and variation in rock resistance to erosion. The mountainous and more complicated southern part of the area has suffered much deformation by igneous intrusions and faulting. The Comanche series is represented by the Devils River limestone, Grayson marl, and Buda limestone. A disconformity separates it from the overlying gradational Gulf series which consists of the Boquillas, Terlingua, and Aguja formations. Because the Boquillas-Terlingua boundary problem is critical and unsettled, lithologic members and paleontologic zones in that section are described in considerable detail. A distinctive 50-foot rock unit, herein named the Fizzle Flat lentil, occurs about the middle of the Boquillas-Terlingua sequence. A widespread angular unconformity separates the Gulf series from the Tertiary Buck Hill volcanic series. Quaternary terrace gravels occur at different levels, and other alluvial deposits have been mapped. The Tertiary hypabyssal igneous rocks are alkalic and form stocks, laccoliths, plugs, sills, dikes, and bysmaliths or trap-door domes. Several lava flows are preserved in the southwest part of the quadrangle. Metamorphic effects generally are slight. The area is part of the Big Bend sunken block. Except where influenced by intrusive masses, a pattern of northwesterly normal faults establishes the structural trend of the area. Step faults are common. Most of the major faults are downthrown to the southwest with the huge intervening blocks tilted gently to the northeast. That much of the fault pattern was established during the Laramide revolution and that faulting recurred along the old lines of weakness fairly late in Tertiary time are postulated.

A New Subspecies of Wedge-Bill from Colombia

The writer has examined only seven specimens from the range postulated for this recently described race. Of these, two juvenal females are useless for comparison. A badly worn and faded adult from Junction is still dark on the rump and a somewhat less worn bird from Kerrville is too dark and dull to be referred to alamoensis. Two specimens from Langtry, however, and another in fresh plumage from the mouth of the Devils River are strikingly of dark, dull coloration, thus differing from all other specimens from other parts of Texas seen by me. Withal, T. 1. oberholseri is apparently completely cut off from geographical contact with ludovicianus, which it most closely resembles, by the much paler and more rufescent T. 1. alamoensis, just as the latter is cut off from T. 1. carolinianus in Ohio and Kentucky by intervention of the darker T. 1. ludovicianus.

Geology of the Santiago Peak quadrangle, Texas

The U. S. Geological Survey topographic sheet of the Santiago Peak quadrangle, Texas, covering 275 square miles, includes the southwestern part of the Marathon uplift, trans-Pecos Texas, where post-Cretaceous folds of the Santiago Mountains cross Paleozoic structural trends. Paleozoic sediments deposited in the Llanoria geosyncline aggregate 15,000 feet and were deformed in Pennsylvanian time by orogenic movements directed from the southeast. The Cretaceous sea, which advanced over beveled Paleozoic strata, deposited 2500 feet of sediments, mostly limestones. The Glen Rose limestone is the oldest Cretaceous formation. The Maxon sandstone may be Fredericksburg in age. The Devils River limestone is divided into four members, two of which can be correlated, at least in part, with the Edwards and the Georgetown formations of central Texas. The Aguja is the youngest Cretaceous formation. Post-Cretaceous doming of the Marathon uplift did not extend west of the Santiago Mountains, in which the chief structural feature is a monocline of Cretaceous strata with the limb overturned to the west. In places the lower flexure of the monocline is broken by a thrust fault, with thrusting from the east. The folding and faulting are believed to have been related to orogeny in the Sierra Madre Oriental 100 miles to the southwest. Large normal faults, trending north-south and northwest-southeast, produced blocks now tilted westward. Post-Cretaceous sills of alkalic syenite occur west of Santiago Mountains.