Browsing by Subject "Big Bend National Park (Tex.)"
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Item A study for the re-use of the Chisos Basin, Big Bend National Park(Texas Tech University, 1996-12) Harms, Rosemary StantonNot availableItem A vertebrate bone-bed in the Aguja formation (Upper Cretaceous), Big Bend National Park, Texas(Texas Tech University, 2001-05) Anglen, John JeffreyAll known specimens of the giant crocodilian Deinosuchus riograndensis have been recovered from a limited stratigraphic interval within the Terlingua Creek Sandstone and upper shale members of the Upper Cretaceous Aguja Formation in Big Bend National Park. The habitat and behavior of this giant crocodile have long been the subject of speculation. A vertebrate bone-bed near Grapevine Hills that includes remains of D. riograndensis as well as a variety of dinosaurs, turtles, and a mesosuchian crocodile provides an opportunity to study the geology, paleontology, and taphonomy of this stratigraphic interval. The Terlingua Creek Sandstone and upper shale members, as observed in the study area, were divided into 3 related sedimentary facies. Deltaic distributary channel deposits are composed of multi-storied, lenticular bodies of trough cross-bedded sandstone with adjacent, inclined heterolithic strata indicative of channel migration. These channel deposits grade into thin, laterally extensive, coarsening-upward sheet sandstones interpreted as crevasse splay deposits. Crevasse splay deposits contain transported logs and resulted from paleocurrents flowing over a 60-degree arc perpendicular to the distributary channel. The sheet sandstones are separated vertically by layers of bioturbated, carbonaceous mudstone interpreted as interdistributary bay and marsh deposits. An extensive bone-bed within one interdistributary deposit contains a single D. riograndensis individual that died in an interdistributary bay or marsh setting. Overbank flooding scattered and aligned some of the remains and winnowed others away. The same interdistributary bay deposit contains remains of hadrosaur. ceratopsian, and ankylosaurian dinosaurs, as well as turtles and mesosuchian crocodiles in transported and attritional assemblages. Fossil wood containing Teredolites borings indicative of brackish-water conditions is intimately mixed with the bones. Thicknesses of sets of trough cross-beds provide minimum water depths of 1.2 to 2.4 meters for the interdistributary bays. The preferred habitat of Z). riograndensis appears to have been these shallow, brackish-water interdistributary bays. All of the other vertebrates in this environment could have been potential prey for D. riograndensis. Although there is no conclusive evidence, such as abundant bite marks on bones, to conclude that D. riograndensis was responsible for the attritional assemblage of vertebrate remains here, this possibility is as likely as others.Item Late Cretaceous and early Tertiary turtles from the Big Bend Region, Brewster County, Texas(Texas Tech University, 1997-05) Tomlinson, Susan L.Fossil turtles are abundant in the Upper Cretaceous and Lower Tertiary sediments of the Aguja, Javelina, and Black Peaks Formations m Big Bend National Park, Brewster County, Texas. Nine genera of freshwater and terrestrial turtles have been identified from these deposits, including Bothremys, "Baena ", Neurmikylus. Compsemys, Adocus, Basilemys. "Aspideretes", "?Helopanoplia" and Hoplochelys. A marine turtle from the Aguja Formation represents a new genus. Turtles are most abundant in the marginal marine, brackish, and freshwater floodplain deposhs of the Aguja Formation, and within the Aguja, they are most abundant in the upper shale member. 'Aspideretes' is the dominant genus in the Upper Cretaceous sediments, followed by "Baena " Turtle fossils are rare in the fluvial floodplain deposhs of the Javehna Formation, where the dominant genus is also Aspideretes." There is a slight increase m abundance and diversity of turtles in the fluvial floodplain deposits of the overlying Black Peaks Formation, where Eoplochelys is the dominant genus. The decrease in numbers and diversity of turtles in the Javelina and Black Peaks formations, compared to the Aguja, was probably the result of a change to dry inland environments less hospitable to turtles. The diversity level of the upper shale member of the Aguja Formation is comparable to that in the correlative Fruitland and Kirtland formations of the San Juan Basin in New Mexico, and to a modem assemblage of turtles in the Brazos River drainage basin in Texas. A comparison of the shell morphologies exhibited in the Aguja fauna and in the Brazos River fauna also suggests that the diversity level is comparable. A morphometric technique was used to determine whether variability in the ornamentation patterns in trionychid shells is useful for taxonomic discrimination. Preliminary results suggest that discrete shell ornamentation patterns are discriminatory and non-random. This technique may be useful for identifying levels of fossil trionychid diversity.Item Mineralogy and geochemistry of paleosols in the Javelina and Black Peaks formations (late Cretaceous-Paleocene), Big Bend National Park, Texas(Texas Tech University, 2000-05) Vines, Carol Marie McNallyA conformable section of Upper Cretaceous and Lower Tertiary sedimentary rocks is exposed on Dawson Creek on the west side of Big Bend National Park, Texas. In this study the upper units of the Javelina Formation and the Black Peaks Formation are analyzed. Through the comparison of selected samples within this section, insights are provided regarding the mineralogy, geochemistry, and depositional history of these formations. All these strata contain presumed soil horizons which are approximately 60-75% smectite clay, while the remaining percentages are made up of detrital grains of monocrystalline quartz, plagioclase feldspar, calcite, and anatase. Iron oxide and manganese oxide permeate all specimens. Micromorphologic features include soil fabrics, voids, illuvial channels and skew planes, cutans, and glaebules. Elemental enrichment and depletion trends are correlated with modern soils. The Dawson Creek sediments display a massive blocky structure with dispersed carbonate nodules and appear similar to modern soils. The mineralogical composition of these deposits indicates that prolonged weathering and leaching did not occur. Micromorphological features indicate translocation and illuviation of material did occur. The similarity in texture, grain size and mineralogy suggests that color differences within these strata did not result form original stratification but occurred due to soil forming processes. This is confirmed by ratios of immobile trace elements. Also, major element abundances differ in each color-banded interval that correspond with color differences. Most of the features observed In the mudstones of the Javelina and Black Peaks Formations are compatible with their interpretation as buried soils (paleosols), however the results of the investigation are not conclusive.Item The effects of changing water availability on the photosynthetic response of plants in the sotol-grasslands of Big Bend National Park, Texas(Texas Tech University, 2003-08) Walker, Erin MThe Hadley Climate Model 11 predicts that Big Bend National Park will receive a 25% increase in both summer and winter rainfall over the next 100 years and that seasonal rainfall patterns will shift from frequent, small storm events to fewer, large storm events. The physiological responses of sotol {Dasylirion leiophyllum) and sideoats grama (Bouteloua curtipendula) to future predicted rainfall patterns were examined over the summer of 2002 through the winter of 2003 in the sotol-grasslands of the Pine Canyon Watershed in Big Bend National Park. Stomatal conductance and photosynthesis were measured for plants that received a 25% increase in seasonal precipitation in either the summer, winter, both the summer and winter, or that received no increase in seasonal rainfall. Stomatal conductance and photosynthesis were also measured for plants that received small, frequent rainfall pulses, rainfall pulses of moderate size and frequency, and large, infrequent rainfall pulses. The 25% increase in seasonal rainfall had no effect on stomatal conductance and photosynthesis for either D. leiophyllum or B. curtipendula, but manipulating rainfall pulses size and frequency did affect the physiological response of the two species. The increase in stomatal conductance and photosynthesis for D. leiophyllum when it received larger, less frequent rainfall pulses, and the favorable response of 5. curtipendula to rainfall pulses of moderate size and frequency suggests that the response of both species is dependent on their rooting habit. Because of its shallow roots, B. curtipendula relied on numerous small pulses to maintain soil water availability in the upper-most soil layers, whereas D. leiophyllum required larger pulses that percolate into its deeper root zone. These results suggest that both species will have a favorable response to the future rainfall patterns predicted by the Hadley Climate Model II.Item The hadrosaurian dinosaurs (ornithiscia: hadrosauria) of Big Bend National Park, Brewster County, Texas, with implications for late Cretaceous paleozoogeography(Texas Tech University, 2001-05) Wagner, Jonathan R.Hadrosaur (Dinosauria: Omithischia) fossils are the most abundant large terrestrial vertebrate fossils in Big Bend National Park. They are most commonly recovered from the Campanian Aguja Formation; predominantly in the upper shale member, rarely in the lower shale member. Hadrosaur fossils are rare in the overlying Late Maastrichtian Javelina Formation, and have also been recovered from the neighboring San Carlos and El Picacho formations of Trans-Pecos Texas. Systematically useful hadrosaur material is commonly found in transported or stream-winnowed tidalcreek deposits, as well as overbank microvertebrate lag deposits. Recovered material most commonly consists of maxillae and postcrania. Examination of new and previously described material from the region allows a greater degree of taxonomic resolution than was previously possible for the hadrosaurs of Big Bend National Park. The Early Campanian lower shale member of the Aguja Formation has produced a partial skull and skeleton, the most complete hadrosaur to date from the Park. The specimen represents a new species of Kritosaurus. This new animal is characterized by an unusual conformation of the rostral mandible, possibly an indication of trophic specialization. Previous reports of Kritosaurus cf. K. navajovius and an indeterminate lambeosaurine are confirmed by new cranial material. The former species is currently not distinguishable from Kritosaurus navajovius from the San Juan Basin, while the latter is distinct from all other known hadrosaurs. Contrary to previous reports of cf. Edmontosaurus from the Javelina Formation, the only diagnostic material from the Javelina clearly pertains to Kritosaurus cf. K navajovius.