Purgatoire River Research Articles

A calibration method for projecting future extremes via a linear mapping of parameters

AbstractIn order to study potential impacts arising from climate change, future projections of numerical model output often must be calibrated to be comparable to observations. Rather than calibrating the data values themselves, we propose a novel statistical calibration method for extremes that assumes there exists a linear relationship between parameters associated with model output and parameters associated with observations. This approach allows us to capture uncertainty in both parameter estimates and the linear calibration, which we achieve via bootstrap. To focus on extreme behavior, we assume both model output and observations have distributions composed of a mixture model combining a Weibull distribution with a generalized Pareto distribution for the tail. A simulation study shows good coverage rates. We apply the method to project future daily-averaged river runoff at the Purgatoire River in southeastern Colorado.

Quantifying the impact of climate extremes on salt mobilization and loading in non-developed, high-desert landscapes using SWAT

Excess salt loading from watershed landscapes into river systems acts as a chemical stressor in water bodies and can have significant impacts on downstream water quality. High salinity threatens sustainable crop production globally and is especially prevalent in semi-arid and arid regions. However, relatively little research has been conducted to evaluate salt movement and loadings in natural, high-desert catchments in the face of climate change and extreme climate events. In this study, we use the watershed model SWAT and a newly developed salinity module to simulate the mass transport of 8 major salt ions, SO42−, Cl−, CO32−, HCO3−, Ca2+, Na+, Mg2+, and K+, in the soil-aquifer-stream system of the Purgatoire River Watershed (PRW) (Colorado, USA, 8935 km2) via major hydrologic pathways (surface runoff, percolation, recharge, soil lateral flow, groundwater upflux, groundwater discharge) and quantify changes in predicted salt loads with possible future increasing storm intensity. The PRW is susceptible to high salt transport due to high topographic slopes, dry climatic conditions, and sparse vegetation, and loads to the Arkansas River, a major source of irrigation water in the Arkansas River Basin. From study results we conclude that 99% of salt in the Purgatoire River originates from subsurface water pathways (soil lateral flow, groundwater flow), composed primarily of SO42−, Ca2+, and HCO3−. If intensity of large storms increases by 5% and 35%, the total salt mass exported from the watershed increases by 12% and 73%, respectively, indicating large influxes of legacy salt from the soil-aquifer system. For baseline and storm intensity scenarios, the PRW contributes significant salt loads to agricultural regions via the Arkansas River, highlighting the need for basin-wide salt management strategies to include upland desert regions. We expect these results, and associated consequences for salt management, to be similar for other upland desert catchments worldwide.

Use of Topographic Map Evidence to Locate a New Cenozoic Glacial History Paradigm’s Deep “Hole” Rim in Northeast New Mexico and Southern Colorado, USA

A recently proposed Cenozoic geology and glacial history paradigm requires a thick North American continental ice sheet to have been located within an ice sheet created and occupied deep “hole” and predicts large south-oriented meltwater floods flowed across the deep “hole’s” southern rim before rim uplift progressively diverted floodwaters toward the Mississippi River valley, which in time became the only deep “hole” southern exit (the accepted paradigm does not recognize such an ice sheet created deep “hole”). Possible locations for the new paradigm deep “hole” rim in Great Plains regions east of the Sangre de Cristo Mountains are considered with the one being the Purgatoire-Canadian River drainage divide in the Raton Mesas area along the Colorado-New Mexico border and a second being the Canadian-Pecos River (Arkansas River-Gulf of Mexico) drainage divide in San Miguel County (NM). Detailed topographic maps indicate streams of what could have been south-oriented melt water once crossed the two studied drainage divides with headward erosion of the northeast-oriented Purgatoire River drainage basin diverting south-oriented water toward the east-oriented Arkansas River (and Mississippi River valley) while headward erosion of east-oriented Canadian River tributary valleys beheaded south-oriented flow to the south-southeast oriented Pecos River (flowing to the Rio Grande River–which then flows to the Gulf of Mexico). While the Purgatoire-Canadian River drainage divide has some deep “hole” rim characteristics, those characteristics disappear in an eastward direction and the Canadian River, like the Purgatoire River, is an Arkansas River tributary. East-oriented Canadian River headwaters and tributary valley headward erosion diverted south-oriented flow from the Rio Grande River to the Mississippi River valley (via the Canadian and Arkansas Rivers), which means the new paradigm’s deep “hole” rim southern margin should be located along or near the Arkansas River-Gulf of Mexico drainage divide.

New sphenodontian (Reptilia: Lepidosauria) from a novel Late Triassic paleobiota in western North America sheds light on the earliest radiation of herbivorous lepidosaurs

AbstractHerbivory is a common ecological function among extant lepidosaurs, but little is known about the origin of this feeding strategy within Lepidosauria. Here we describe a sphenodontian (Lepidosauria) from the Late Triassic of western North America,Trullidens purgatoriin. gen. n. sp., that reveals new aspects of the earliest radiation of herbivorous lepidosaurs. This taxon is represented by an isolated lower jaw with robust structure bearing transversely widened dentition and extensive wear facets, suggesting a masticatory apparatus specialized for herbivory. An unusual ‘incisor-like’ tooth is present at the anterior end of the jaw; a unique feature among lepidosaurs, this tooth is convergent with the incisors of extant rodents and lagomorphs. Phylogenetic analyses support the placement of this taxon within opisthodontian sphenodontians, a group sharing derived cranio-dental morphologies specialized for herbivory. The new taxon was recovered in a recently discovered and unnamed series of Upper Triassic strata in southeastern Colorado, USA, exposed in Canyons incised by the Purgatoire River and its tributaries. These strata comprise a dominantly red-bed sequence of conglomerates, sandstones, and siltstones deposited in a fluvio-lacustrine setting, preserving a Late Triassic biota of invertebrate and vertebrate ichnofossils, plant macrofossils, bony fish, temnospondyl amphibians, and reptiles. We use aetosaur osteoderms as biostratigraphic links to the nearby Chinle Formation of Arizona, USA, establishing a middle Norian age for these strata. The presence of an opisthodontian from western equatorial Pangaea in the Norian Stage reveals a near-global radiation of this clade across the Pangaean supercontinent during the Late Triassic.UUID:http://zoobank.org/A737c03f-863a-488e-a860-5cc914548774.

Redefining the Upper Jurassic Morrison Formation in Garden Park National Natural Landmark and vicinity, eastern Colorado: Geology of the Intermountain West

The Garden Park National Natural Landmark (GPNNL) is north of Cañon City, Colorado, and encompasses all of the major historical dinosaur quarries of the Upper Jurassic Morrison Formation in this area. The formation there can be divided into the lower redefined Ralston Creek Member and an upper unnamed member. The Morrison Formation is bracketed below by the J-5 unconformity and above by the K-1 unconformity. The Ralston Creek Member is composed of up to 55 m of arkosic conglomerate, sandstone, siltstone, and gypsum conformably underlying the unnamed member. Fossil fishes previously used to infer a Middle Jurassic age are non-diagnostic. A diplodocid skeleton 4 m above the J-5 unconformity from the west-adjacent Shaws Park, and a radiometric date of 152.99 + 0.10 Ma from the Purgatoire River area demonstrate that the Ralston Creek rightly belongs in the Morrison Formation and correlates with the Tidwell and Salt Wash Members on the Colorado Plateau. The Ralston Creek was deposited in a broad playa complex analogous to those of central Australia and here called the Ralston Creek boinka. Groundwater flux played an important role in gypsum deposition in gypsisols and playa lakes. The overlying unnamed member in the GPNNL can be subdivided on the west side of Fourmile Creek into a lower part composed largely of mudstone with many thin, discontinuous channel sandstone beds, and a thicker upper part containing more persistent tabular sandstone beds; this subdivision does not occur east of Fourmile Creek. Several thin limestone beds occur in the Ralston Creek Member and in the lower part of the unnamed upper member. The limestone contains fresh water ostracods and aquatic mollusks indicating a lacustrine origin. However, these fauna are apparently stunted and the ostracod valves closed indicating periodic hypersaline conditions. All detrital rocks in the Morrison Formation at Garden Park are composed of varying amounts of quartz, potassic feldspar, and the clay minerals illite, smectite, and kaolinite. Mapping of the clay minerals in the unnamed member reflect various paleosols throughout the mudstone interval, including protosols and argillisols. At the top of the formation, a sandstone previously assigned to the Morrison is reassigned to the overlying Cretaceous Lytle Formation based on similar weathering characteristics, mineral content, and fabric. Thus, the K-1 unconformity between the Morrison and overlying Lytle rests on the uppermost occurrence of the Morrison Formation mudstone-sandstone-limestone complex and beneath the blocky, cliff-forming Lytle Formation.

Redefining the Upper Jurassic Morrison Formation in Garden Park National Natural Landmark and vicinity, eastern Colorado: Geology of the Intermountain West

The Garden Park National Natural Landmark (GPNNL) is north of Cañon City, Colorado, and encompasses all of the major historical dinosaur quarries of the Upper Jurassic Morrison Formation in this area. The formation there can be divided into the lower redefined Ralston Creek Member and an upper unnamed member. The Morrison Formation is bracketed below by the J-5 unconformity and above by the K-1 unconformity. The Ralston Creek Member is composed of up to 55 m of arkosic conglomerate, sandstone, siltstone, and gypsum conformably underlying the unnamed member. Fossil fishes previously used to infer a Middle Jurassic age are non-diagnostic. A diplodocid skeleton 4 m above the J-5 unconformity from the west-adjacent Shaws Park, and a radiometric date of 152.99 + 0.10 Ma from the Purgatoire River area demonstrate that the Ralston Creek rightly belongs in the Morrison Formation and correlates with the Tidwell and Salt Wash Members on the Colorado Plateau. The Ralston Creek was deposited in a broad playa complex analogous to those of central Australia and here called the Ralston Creek boinka. Groundwater flux played an important role in gypsum deposition in gypsisols and playa lakes. The overlying unnamed member in the GPNNL can be subdivided on the west side of Fourmile Creek into a lower part composed largely of mudstone with many thin, discontinuous channel sandstone beds, and a thicker upper part containing more persistent tabular sandstone beds; this subdivision does not occur east of Fourmile Creek. Several thin limestone beds occur in the Ralston Creek Member and in the lower part of the unnamed upper member. The limestone contains fresh water ostracods and aquatic mollusks indicating a lacustrine origin. However, these fauna are apparently stunted and the ostracod valves closed indicating periodic hypersaline conditions. All detrital rocks in the Morrison Formation at Garden Park are composed of varying amounts of quartz, potassic feldspar, and the clay minerals illite, smectite, and kaolinite. Mapping of the clay minerals in the unnamed member reflect various paleosols throughout the mudstone interval, including protosols and argillisols. At the top of the formation, a sandstone previously assigned to the Morrison is reassigned to the overlying Cretaceous Lytle Formation based on similar weathering characteristics, mineral content, and fabric. Thus, the K-1 unconformity between the Morrison and overlying Lytle rests on the uppermost occurrence of the Morrison Formation mudstone-sandstone-limestone complex and beneath the blocky, cliff-forming Lytle Formation.

Recent northward range expansion of the parthenogenetic lizardAspidoscelis tesselatusin Colorado and the distributional enigma posed by pattern-classes C and D at the northern range periphery

The range of the parthenogenetic lizard Aspidoscelis tesselatus extends from eastern Chihuahua, Mexico, to southeastern Colorado, USA. In Colorado, pattern-class D, source of the neotype of the species, is syntopic with the more widely distributed pattern-class C only in Ninemile Valley of the Purgatoire River, beyond which, in all directions, these pattern classes are allopatric. We identify a recent northward range expansion of pattern-class C to the same northern latitude attained by pattern-class D, thereby establishing a latitudinal baseline for the species. The two northern arrays of pattern-class C, reported herein, occupied open habitats of sparsely distributed shrubs on rocky slopes, whereas the northernmost arrays of pattern-class D were using juniper woodland. Although this allopatric arrangement suggests ecological segregation of pattern classes, we provide an example of pattern-class C in juniper woodland only ca. 11 km south of the new records, which suggests that other factors could be involved.

A Dynamic Flow Regime Supports an Intact Great Plains Stream Fish Assemblage

AbstractIntact native fish assemblages—those with all or most historical taxa present and a strong numerical dominance of native species—are rare in streams and other aquatic systems worldwide. Our sampling during four intervals from 1983 to 2007 showed that the Purgatoire River, a Great Plains stream in eastern Colorado, supported an assemblage that was 99.6% native taxa, and all but one rare species persisted through time. An additional rare Arkansas River native fish colonized the Purgatoire River and was widespread in 2006–2007, and only three nonnative taxa were detected. The perennial Purgatoire River supported all native fishes in the basin, while tributaries supported mainly native fishes that were tolerant of intermittent, harsh habitat. In the Purgatoire River, frequency and abundance of dominant species varied spatially during 2006–2007. Persistence of native fishes was unchanged over time in the Piñon Canyon reach of the river even though abundance varied substantially. Despite the presence of upstream Trinidad Reservoir, which reduced flood peak magnitude and frequency and increased base flows, the flow regime of the river remained flashy, with high, turbid, and unpredictable flood flows. Peak flows resulted from thunderstorms in tributaries of the Purgatoire River downstream from the reservoir or from snowmelt runoff and usually occurred in August or July but also were observed in May and June. We attribute persistence of the native fish assemblage to sustained base flows and, more importantly, to the continued (albeit lower) magnitude and frequency of peak flows and otherwise harsh habitat, which limit invasion by nonnative fishes from upstream and downstream reservoirs. Persistence of the intact native fish assemblage in the Purgatoire River requires maintenance of the dynamic flow regime and prevention of invasions by nonnative fishes, including riverine‐adapted centrarchids like Smallmouth Bass Micropterus dolomieu. Conservation of the Purgatoire River basin should be a priority for ecologists and managers alike given its value as a study system and as habitat for rare fishes.Received July 18, 2016; accepted March 20, 2017 Published online July 11, 2017

An occurrence of coked bitumen, Raton Formation, Purgatoire River Valley, Colorado, U.S.A.

Numerous examples of coke produced by igneous intrusion into coal have been reported in the Spanish Peaks region of south central Colorado. However, in a recent study of an intruded section of the Raton Formation (Upper Cretaceous-Paleocene) along the Purgatoire River near Medina Plaza, CO, coked bitumen has been observed. This material occurs in “fingers” (hexagonally jointed bodies) in a shaley xenolith within a lamprophyre sill and in carbonaceous Type III shale directly below the sill. The coke fingers are characterized by a remarkable flow mosaic texture, high vitrinite/coke reflectance (average random reflectance between 8% and 9%, but with maximum readings around 14–15%), high anisotropy, abundant devolatilization vacuoles, and an absence of inertinite inclusions. Within the underlying shales, the coked bitumen occurs as pore, void, and fracture linings and fillings. Geochemically, the coke in the fingers has low S1 and S2 values (<0.2 and <3mg HC/g, respectively), and low HI and OI values (<6mg HC/g TOC and <3mg CO2/g TOC, respectively). Within the fingers, there is evidence for multiple stages of accumulation, including coarse-grained circular or ribbon coke frequently containing pores edged by vapor-deposited carbon (pyrolytic carbon), layers of pyrolytic carbon, clusters of spherulitic pyrolytic carbon, and layers of highly porous coke. This coked bitumen is quite different from coked coal from the same locality. The coked coal has a medium-grained circular mosaic texture that is consistent with the high volatile bituminous rank of unaltered coal in the area. The coal-derived coke has similar devolatilization vacuoles but also has numerous inclusions of inertinite macerals such as fusinite and secretinite. A previously reported coal “dike” that had flowed through a sill in the same area also showed circular mosaic texture.These observations suggest that the coke found in this study was not formed by the direct coking of coal, but from a mobile phase (bitumen or pitch) that was subsequently coked by the intrusion. This bitumen was either derived from the abundant coal within the section above the sill, or from the organic matter contained within the Type III carbonaceous shales, or both. Unaltered Type III shale sampled at this site has a HI of ~350mg HC/g TOC suggesting some, albeit limited, capacity to generate petroleum. We suggest that bitumen was generated prior to or during the time of intrusion and was subsequently coked by the high temperatures of the emplaced sill. As the bitumen pooled adjacent to the sill, rapid heating led to the development of mesophase, resulting in a highly anisotropic ribbon mosaic texture on cooling, and vaporization of gases that subsequently condensed along pores, vacuoles, and fractures as pyrolytic carbon and spherulitic pyrolytic carbon. Bitumen within the underlying silty shales was also coked, but to a lesser degree. The texture of this coked bitumen looks very much like commercially produced petroleum coke. This coked bitumen differs from other reports of coked bitumen in its mode of occurrence (coke fingers in a xenolith), ribbon mosaic structure, and extremely high anisotropy and reflectance.

Characteristics of Roosts of Male Pallid Bats (Antrozous pallidus) In Southeastern Colorado

Abstract Male pallid bats (Antrozous pallidus) from the Purgatoire River Valley of northern Las Animas County, Colorado, were fitted with telemeters and followed to 53 day roosts. A majority of roosts were in cliffs (89%), with fewer in free-standing rocks at the base of cliffs. Temperatures at roosts were moderate (27°C) but warmer than ambient temperatures. Roosts in cliffs were slightly warmer than ambient temperatures, while roosts in rocks usually were 5°C greater than ambient temperatures. Typically, bats roosted in crevices that faced east or southeast with much solar exposure. Roosts in cliffs were in long, narrow cracks that extended into the face of the rock. The high temperatures recorded at roosts of male pallid bat may be advantageous for regulating body temperature, avoiding costly torpor bouts, or preparing for reproduction.

Pattern-Class D of Parthenogenetic Aspidoscelis tesselata (Sauria: Teiidae) in Las Animas County, Colorado

Abstract The diploid, parthenogenetic, whiptail lizard Aspidoscelis tesselata is represented by two distinctive variants of color pattern in southeastern Colorado. Pattern-class C has been recorded from several sites in the canyonlands of Otero, Las Animas, and Baca counties and D has been recorded from four sites north of the Purgatoire River near Higbee, Otero County. We report a specimen of A. tesselata D collected in 2008 south of the Purgatoire River in Las Animas County, which represents a significant range extension for this distinctive parthenogen.

WESTWARD EXPANSION OF THE EASTERN FOX SQUIRREL (SCIURUS NIGER) IN NORTHEASTERN NEW MEXICO AND SOUTHEASTERN COLORADO

Abstract The eastern fox squirrel (Sciurus niger) has continued to move westward along riparian corridors in the southwestern United States. This species is now established along the Arkansas River and its major tributaries in southeastern Colorado. In addition, a population of S. niger exists in northern New Mexico, and this population might be the result of natural expansion from populations along the Purgatoire River in southeastern Colorado.

Hybrid Cnemidophorus (Sauria: Teiidae) in Ninemile Valley of the Purgatoire River, Colorado

Canonical variate analysis (CVA) of color pattern and scutellation characters in lizards collected in Ninemile Valley of the Purgatoire River at Higbee, Otero Co., Colorado graphically depicted two forms of parthenogenetic Cnemidophorus tesselatus (diploid color pattern class C and triploid color pattern class B), gonochoristic C. sexlineatus, and hybrid C. tesselatus x C. sexlineatus as four morphologically distinctive groups. A newly obtained male specimen with a C. tesselatus-like color pattern entered as an unknown was classified to the hybrid group in the CVA. It represented the fourth tetraploid hybrid C. tesselatus B(3n) x C. sexlineatus collected in the valley. A female specimen was also classified to the hybrid group by the CVA. A triploid karyotype (3n = 69) and color pattern identified this female as a putative C. tesselatus C(2n) x C. sexlineatus hybrid. Whereas male hybrids are presumably sterile and biological novelties at most, the possibility remains that a female hybrid could be the founder of a new parthenogenetic lineage. Zweifel (1965) informally described six color pattern classes of parthenogenetic lizards (A, B, C, D, E, F) in the Cnemidophorus tesselatus complex (family Teiidae) of which four (A-D) were reported from Colorado. Wright and Lowe (1967a) found that pattern classes A and B were triploid hybrid derivatives and pattern classes CF were diploid hybrid derivatives. Analyses of morphology (Walker et al., 1990) and karyology (Cordes, 1991) identified three of Zweifel's pattern classes of C. tesselatus in sympatry in Ninemile Valley of the Purgatoire River at Higbee, Otero Co., Colorado rather than two as indicated by Zweifel (1965), Densmore et al. (1989), and Wright (1993). These included diploid C. tesselatus C and D and triploid B, not triploid pattern class C as indicated by Parker and Selander (1976), Densmore et al. (1989), Wright (1993), and Leuck (1993). We found that the Ninemile Valley triploid population was morphologically indistinguishable from the pattern class B population described by Zweifel (1965) from Pueblo Co., Colorado. In samples collected in the valley since 1960 by various workers, diploid C. tesselatus outnumbered triploid C. tesselatus by a combined ratio of over 7:1. Moderate numbers of the gonochoristic species C. sexlineatus, the paternal parent of triploid C. tesselatus B (Wright and Lowe, 1967a; Parker and Selander, 1976), were also found in many parts of the area sampled. Four hybrid male C. tesselatus x C. sexlineatus were included in these collections. Three of these were described, and their probable parental forms identified as triploid C. tesselatus B x C. sexlineatus, by Walker et al. (1990). In the present study we describe the most recently collected hybrid male Cnemidophorus, infer its putative parentage on the basis of critical morphological characters, and evaluate the possibility of a hybrid origin for a female specimen displaying an ambiguous combination of classification characters. MATERIALS AND METHODS-Characters of scutellation that were quantitatively analyzed included: number of granules around midbody (GAB), number of granules from occiput to rump (OR), sum of left and right femoral pores (FP), number of subdigital lamellae on the longest toe of the left pes (SDL), sum of left and right circumorbital scales (COS), sum of This content downloaded from 207.46.13.57 on Mon, 08 Aug 2016 05:24:23 UTC All use subject to http://about.jstor.org/terms 236 The Southwestern Naturalist vol. 39, no. 3

Variable Fish Communities and the Index of Biotic Integrity in a Western Great Plains River

We applied the index of biotic integrity (IBI) to the portion of the Arkansas River basin within the Southwestern Tablelands ecoregion, located on the Great Plains of southeastern Colorado. Only nine IBI metrics were appropriate for this region, largely because of the depauperate and tolerant ichthyofauna. The modified index was then used to assess effects of U.S. Army mechanized infantry training on biotic integrity of the Purgatoire River at 12 sites adjacent to the Pifion Canyon Maneuvers Site, a remote and relatively undisturbed canyon reach on a seventh-order Arkansas River tributary. Decrease in abundance of adult red shiners Cyprinella lutrensis, a tolerant omnivorous species, over a 6-year period (1983–1989) caused marked increases in the IBI at 9 of 12 sites despite lack of obvious changes in environmental quality after training began in 1985. Neither sampling variation nor the magnitude and timing of floods were sufficient to explain the large decrease in red shiner abundance. Other attributes of the biota, such as presence of long-lived fishes and lack of introduced species, provided no evidence for detrimental change. The majority of potential IBI metrics were hampered by the low fish species richness, the preponderance of trophic and habitat generalists, or other attributes of the depauperate ichthyofauna. Moreover, human perturbations that cause change in fish communities of midwestern U.S. streams are suspected in many cases to mimic natural disturbances in this system, so they may have relatively little effect. Conversely, some perturbations considered benign in more mesic environments are likely to cause dramatic changes. We therefore propose that our understanding of the structure, function, and natural variation of fish communities in western Great Plains streams must increase substantially before we can define fully appropriate measures of biotic integrity for these lotic systems.

Fishes, Macroinvertebrates, and Aquatic Habitats of the Purgatoire River in Pinon Canyon, Colorado

We describe physical habitat and aquatic biota of a relatively undisturbed canyon reach of the Purgatoire River and its tributaries in southeastern Colorado. Flow regimes are highly variable due to unpredictable, brief, intense summer floods. River habitat consists of long, deep, silty pools with few large boulders separated by short cobble riffles, whereas tributaries contain isolated pools maintained by groundwater. Water chemistry and temperatures were within ranges tolerable by plains stream fishes at all sites. Benthic macroinvertebrate assemblages included representatives of four regional faunas. At lotic sites, a few taxa of two detritus-collecting functional groups predominated. The fish fauna is depauperate, consisting of only 11 native species which we divided into river, perennial stream, and generalist faunal associations. However, most fishes have generalized habitat, trophic, and reproductive requirements, which seem to adapt them to survive the harsh environmental conditions in this plains stream. Although the four species that made up 95% of individuals generally persisted at river sites over the 5to 7-year period sampled, the abundance of red shiners declined markedly from 1983 to 1987 despite favorable flow regimes. Little is known of the ecology and physical characteristics of streams of the western Great Plains (Matthews, 1988). However, fish and macroinvertebrate assemblages in such systems can be expected to differ from those in more mesic regions due to extremes in physical characteristics such as flow, turbidity, and temperature. Relatively pristine habitats in streams of the western plains are scarce due to a profusion of human activities, such as channelization, damming, dewatering, mining, overgrazing, use of agricultural chemicals, release of municipal and industrial wastes, and the introduction of nonnative species (Cross and Moss, 1987). Although the Purgatoire River is not immune to these perturbations, the reach we discuss here is one of few comparatively undisturbed remnants in the region and, therefore, offers an opportunity to study habitat and aquatic biota in a relatively natural stream of the western plains. The purpose of this paper is to describe the flow regime, physical habitat, and water chemistry of the Purgatoire River and its tributaries in Pifion Canyon and to document the species composition, distribution, and ecological characteristics of assemblages of benthic macroinvertebrates and fishes of these waters. Few reports of aquatic biota exist for this general area (Cope and Yarrow, 1875; Jordan and Evermann, 1891; D. Vana-Miller, in litt.), and none for the specific reach. We show that this reach harbors depauperate assemblages of entirely native aquatic biota which have generalized ecological requirements that adapt them for persistence in plains

Hybridization between All-Female Cnemidophorus tesselatus and Gonochoristic Cnemidophorus sexlineatus

Both triploid (TES-B(3n)) and diploid (TES-C(2n) and TES-D(2n)) lineages of all-female, normally parthenogenetic Cnemidophorus tesselatus are sympatric with gonochoristic C sexlineatus viri- dis in Ninemile Valley of the Purgatoire River at Higbee, Otero County, Colorado. An adult, a subadult, and a juvenile hybrid male C. tesselatus x C. sexlineatus were collected in 1973,1988, and 1989, respectively, in microhabitats where all of the possible parental forms were found. Scutellation, color pattern, and electrophoretic data identified TES-B(3n) as the maternal parent of the adult hybrid, and the presence of four bands at the albumin locus confirmed that it is tetraploid. The subadult and juvenile males also appear to represent tetraploid hybrid TES-B(3n) x C. sexlineatus based upon color pattern and univariate and multivariate analyses of scutellation data. Female TES-B(3n) achieve sexual maturity at a significantly smaller size than either TES-C(2n) or TES-D(2n) at Higbee; this makes insemination of female TES-B(3n) by adult male C sexlineatus more likely, and also favors the hypothesis of TES-B(3n) parentage for the two hybrids. All evidence of continuing hybridization between any of these all-female forms and C. sexlineatus is significant since it provides a basis for the inference that hybrid females with the potential of founding new parthenogenetic lineages of Cnemidophorus may also be produced.

North America's largest dinosaur trackway site: Implications for Morrison Formation paleoecology

Little-known exposures of the Upper Jurassic Morrison Formation from the Purgatoire Valley of southeastern Colorado have yielded the world's largest continuously mapped assemblage of dinosaur trackways. Body fossils include plant, invertebrate, and vertebrate remains indicative of predominantly fresh-water conditions. The tracks occur in a lacustrine sequence characterized by (1) shallow-water shales; (2) micritic shoreface limestones with ooids, intraclasts, ripple marks, mud cracks; and (3) minor quartzose sandstone with salt-crystal casts. Analysis of these sedimentary facies suggests that in southeastern Colorado, lakes were larger and longer lived than in other Morrison paleoenvironments. Trackway orientations and footprint-depth contours pinpoint the location of the paleoshoreline at successive levels in the section. Detailed mapping of 1,300 footprints in bed 2 has revealed more than 100 trackways which testify to the activity of both quadrupedal and bipedal dinosaurs. The respective ratio based on trackway counts is ∼40/60. The quadrupedal tracks are attributed to sauropods, and represent the first ever discovered in North America. They also exhibit the first known manus claw impressions and are in need of formal description. More than 90% of the bipedal tridactyl prints lack claw impressions and are tentatively therefore referred to the Ornithopoda, cf. Gypsichnites possibly a Camptosaurus . The small proportion with distinct claw impressions may represent Allosaurus . Resulting estimates of species diversity (∼5) and predator-prey ratio (1:30) are in general agreement with the estimates of other authors based on skeletal remains, and they suggest that the Purgatoire River tracks may accurately reflect the composition of the dinosaur fauna. Distinctive groupings of parallel, non-overlapping trackways suggest gregarious behavior among sauropods and tridactylous forms.

Coal dikes that intrude lamprophyre sills; purgatoire river valley, Colorado

Fluidization of coal by heat from adjacent lamprophyric sills, injection by lithostatic pressure into fractures in partially cooled sills, metamorphism of dike subsequent to injection

A Petrologic Study of a Thermally Altered Coal from the Purgatoire River Valley of Colorado

A column of coal from a seam thermally altered by an underlying lamprophyric sill has been studied petrographically, chemically, and mineralogically. Megascopically there are four major lithotypes present within the limits of the seam. They are: carbonaceous shale, natural coke, altered coal, and a layer of quartz grains. Megascopic evidence indicative of thermal alteration is the highly contorted bedding, natural coke with evidence of flowage, and prismatic fracturing within the highly altered coal zones. Micrinoids and fusinoids are common, with the cell cavities of the fusinoids commonly filled with calcite. Vitrinoids are all altered to a dark-brown color in thin section. Fungal derived bodies are common in the upper part of the seam and appear to be the most thermally resistant petrographic entities. No evidence of spore or cuticular material remains. Mosaic structure and vesiculation are additional common microscopic evidences for the thermal alteration. Sulfur distribution apparently has no relation to the presence of the intrusion. Ash values are highest at the top and bottom of the seam and are related to shale-rich zones. Volatile matter (d.a.f.) is high at the seam margins and increases as the distance from the intrusion decreases. This is attributed to one, or both, of two factors. Either the volatiles were released and readsorbed or they were never released. Only quartz, kaolinite, siderite, calcite, and Fe 2 (SO 4 ) 3 were identified by X-ray examination. No evidence of the presence of cristobalite, mullite, or pyprophyllite was detected. Mean maximum reflectance values range from 1.00 percent to 3.00 percent and increase toward the intrusion. Evidence based on mineralogy, chemistry, reflectance, melting point, and electron spin resonance indicates that a temperature gradient did exist across the seam from greater than 375° C at the top to less than 600° C at the base, and also that the temperature of the underlying shale at the contact with the sill was not more than 600° C.

Probable Triassic Rocks Along Eastern Front of Sangre de Cristo Mountains, South-Central Colorado

Sedimentary rocks of Triassic age generally have been thought to be missing from outcrops in the Sangre de Cristo Mountains of Colorado where at most places the Entrada sandstone of Jurassic age rests unconformably on rocks that have been assigned to the Sangre de Cristo formation of Pennsylvanian and Permian age. Two units of probable Triassic age have been separated from the top of the Sangre de Cristo formation; one is here described and named the Johnson Gap formation. The other is correlated with the Lykins formation of central Colorado and in this report is referred to as the Lykins(?) formation. The Johnson Gap formation crops out for 8 mi. or more N. of the Colorado-New Mexico boundary, and is correlated with a part of the Dockum group of Triassic age of northern New Mexico. The Lykins(?) formation crops out in the area of Huerfano Park and locally along the eastern front of the Sangre de Cristo Mountains as far S. as the North Fork of the Purgatoire River. Fossil wood found near the top of the unit has been determined as Triassic(?) in age. The Johnson Gap formation and the Lykins(?) formation differ lithologically and probably are not correlative. The Johnson Gap consists mainly of gray silty conglomeratic limestone interbedded with gray and light red silty and siliceous limestone, red siliceous siltstone, greenish gray and brown plastic shale, and gray fine-grained quartzose sandstone. The Lykins(?) is made up of brownish red, purplish red, and buff sandstone, siltstone, and shale, and a few thin light gray limestone beds. It is probably older than the Johnson Gap formation in that the Lykins(?) formation seems to grade into the underlying Sangre de Cristo formation, whereas the Johnson Gap formation overlies the Sangre de Cristo unconformably. The striking lithologic similarity of the rocks of the Lykins(?) formation along the eastern front of the Sangre de Cristo Mountains to those of the most southerly exposures of the Lykins formation 20 mi. ENE. of Canon City, Colorado, suggests that the rocks once were probably continuous throughout S.-central Colorado, but were locally removed by erosion following a post-Triassic uplift in the general area of the Wet Mountains.