Biodemography of ectothermic tetrapods provides insights into the evolution and plasticity of mortality patterns
No abstract available.
California, Illinois↗
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Population dynamics of sea ducks: using models to understand the causes, consequences, evolution, and management of variation in life history characteristics
In this chapter, I explore population dynamics of sea ducks by developing population models. In determining which life history characteristics had the greatest influence on future population dynamics, adult female survival consistently had the highest sensitivity and elasticity and this result was robust across a wide range of life history parameter values. Conversely, retrospective models consistently found that the majority of annual variation in lambda was associate with variation in productivity. Stochastic models that are base on process variation and incorporate correlations among life history parameters are the most useful for visualizing the probability of achieving a desired management outcome. Effective management targets both the mean and the variance parameters and takes advantage of correlations among life history parameters. Example models demonstrate that sea duck species can achieve equal fitness using a variety of survival and productivity combinations. Sea duck populations will tend to have long time largest in terms of responding to management actions. Understanding the role of density-dependent population regulation is critical for effective sea duck management and conservation.
Book chapter↗
Linking human impacts within an estuary to ebb-tidal delta evolution
San Francisco Bay, California, USA is among the most anthropogenically altered estuaries in the entire United States, but the impact on sediment transport to the coastal ocean has not been quantified. Analysis of four historic bathymetric surveys has revealed large changes to the morphology of the San Francisco Bar, an ebb-tidal delta at the mouth of the San Francisco Bay. From 1873 to 2005 the bar eroded an average of 80 cm, which equates to a total volume loss of 100 + 65 x 10 6 m 3 of sediment. Comparison of the surveys indicates the entire ebb delta has contracted radially while its crest has moved landward an average of 1 km. Compilation of historic records reveals that 130 x 106 m 3 of sediment has been permanently removed from the San Francisco Bay and adjacent coastal ocean. Constriction of the bar is hypothesized to be from a decrease in sediment supply from San Francisco Bay, a reduction in the tidal prism of the estuary, and/or a reduction in the input of hydraulic mining debris. Changes to the morphology of the San Francisco Bar have likely altered wave refraction and focusing patterns on adjacent beaches and may be a factor in persistent beach erosion occurring in the area.
California↗
Using dissolved gases to observe the evolution of groundwater age in a mountain watershed over a period of thirteen years
Baseflows in snowmelt-dominated mountain streams are critical for sustaining ecosystems and water resources during periods of greatest demand. Future climate predictions for mountainous areas throughout much of the western U.S. include increasing temperatures, declining snowpacks, and earlier snowmelt periods. The degree to and rate at which these changes will affect baseflows in mountain streams remains unknown, largely because baseflows are groundwater-fed and the relationship between climate and groundwater recharge/discharge rates in mountain watersheds is uncertain. We use groundwater age determinations from multiple dissolved gas tracers (CFCs, SF6, and 3H/3He) to track changes in groundwater age over a period of thirteen years in the Sagehen Creek watershed, Sierra Nevada Mountains, CA. Data were collected from springs and wells in 2009 and 2010 and combined with those obtained in prior studies from 1997 to 2003. Apparent ages range from 0 to >60 years. Comparison between variations in age and variations in snow water equivalent (SWE) and mean annual air temperature reveals the degree of correlation between these climate variables and recharge rate. Further, comparison of apparent ages from individual springs obtained at different times and using different tracers helps constrain the age distribution in the sampled waters. The age data are generally more consistent with an exponential age distribution than with piston-flow. However, many samples, even those with relatively old mean ages, must have a disproportionately large very young fraction that responds directly to annual SWE variations. These findings have important implications for how future baseflows may respond to decreasing SWE.
California↗
Grain-size evolution in suspended sediment and deposits from the 2004 and 2008 controlled-flood experiments in Marble and Grand Canyons, Arizona
Since the closure of Glen Canyon Dam in 1963, the hydrology, sediment supply, and distribution and size of modern alluvial deposits in the Colorado River through Grand Canyon have changed substantially (e.g., Howard and Dolan, 1981; Johnson and Carothers, 1987; Webb et al., 1999; Rubin et al., 2002; Topping et al., 2000, 2003; Wright et al., 2005; Hazel et al., 2006). The dam has reduced the fluvial sediment supply at the upstream boundary of Grand Canyon National Park by about 95 percent. Regulation of river discharge by dam operations has important implications for the storage and redistribution of sediment in the Colorado River corridor. In the absence of natural floods, sediment is not deposited at elevations that regularly received sediment before dam closure. There has been a systemwide decrease in the size and number of subaerially exposed fluvial sand deposits since the 1960s, punctuated by episodic aggradation during the exceptional high-flow intervals in the early 1980s and by sediment input from occasional tributary floods (Beus and others, 1985; Schmidt and Graf, 1990; Kearsley et al., 1994; Schmidt et al., 2004; Wright et al., 2005; Hazel et al., 2006). Fluvial sandbars are an important component of riparian ecology that, among other functions, enclose eddy backwaters that form native-fish habitat, provide a source for eolian sand that protects some archaeological sites, and are used as campsites by thousands of river-runners annually (Rubin et al., 1990; Kearsley et al., 1994; Neal et al., 2000; Wright et al., 2005; Draut and Rubin, 2008).
Arizona↗
Architecture and evolution of an Early Permian carbonate complex on a tectonically active island in east-central California
The newly named Upland Valley Limestone represents a carbonate complex that developed on and adjacent to a tectonically active island in east-central California during a brief interval of Early Permian (late Artinskian) time. This lithologically unique, relatively thin limestone unit lies within a thick sequence of predominantly siliciclastic rocks and is characterized by its high concentration of crinoidal debris, pronounced lateral changes in thickness and lithofacies, and a largely endemic fusulinid fauna. Most outcrops represent a carbonate platform and debris derived from it and shed downslope, but another group of outcrops represents one or possibly more isolated carbonate buildups that developed offshore from the platform. Tectonic activity in the area occurred before, probably during, and after deposition of this short-lived carbonate complex.
California↗
Halogen contents of igneous minerals as indicators of magmatic evolution of rocks associated with the Ray porphyry copper deposit, Arizona
The contents of Cl, F, and H 2 O+ (calculated) in some hydrous igneous minerals in intrusive rocks of Laramide age (70-60 m.y.) near Ray, Ariz., appear to be related to the age and the chemistry of the whole-rock samples. Apatite and biotite in younger, more silicic rocks contain more F but less Cl and H 2 O+ than apatite and biotite in older, more mafic rock; the same relations hold for F and H 2 O+ in sphene. Correlations of the abundance of Cl, F, and H 2 O+ in hornblende with rock chemistry and age are not as strong as for apatite, biotite, and sphene; igneous (?) epidote does not contain Cl and F in amounts detectable by electron microprobe analysis. The contents of Cl, F, and H 2 O+ in whole-rock samples decrease with increasing differentiation index and decreasing age. Data for a single pluton of variable composition mirror the results for a suite of different plutons and dikes. The data are satisfactorily although not exclusively explained by postulating that the melts each contained progressively less Cl, F, and H 2 O and that the hydrons minerals consumed most of the Cl, F, and H 2 O in the magmas. The data may also be explained by postulating that (1) the stocks evolved Cl-bearing water during their ascent and crystallization, or that (2) Cl and H 2 O were concentrated during differentiation of the stocks but the minerals failed to record their buildup. Both alternative explanations find problems with and require special conditions to satisfy field, chemical, and experimental data. If many of the special conditions are not met, a nearby batholithic parent to the stocks is not a favorable source of the mineralized fluids at Ray. Propylitic alteration of biotite results in Cl-poor chlorites and may have provided some Cl to hydrothermal fluids; biotite may have also supplied some F to propylitizing fluids through alteration.
Arizona↗
Late Neogene deformation of the Chocolate Mountains Anticlinorium: Implications for deposition of the Bouse Formation and early evolution of the Lower Colorado River
Deformation related to late Neogene dextral shear can explain a shift from an estuarine to lacustrine depositional environment in the southern Bouse Formation north of Yuma, Arizona. We infer that late Neogene deformation in the Chocolate Mountain Anticlinorium (CMA) created a barrier that blocked an estuary inlet, and that pre-existing and possibly active structures subsequently controlled the local course of the lower Colorado River. Structural patterns summarized below suggest that the CMA absorbed transpressional strain caused by left-stepping segments of dextral faults of the San Andreas fault system and/or the eastern California shear zone and Gulf of California shear zone. For this hypothesis to be correct, about 200-250 m of post-6 Ma, pre- ~5.3 Ma uplift along the CMA crest would be required to cut off a marine inlet. The 220-km-long CMA, cored by the early Paleogene Orocopia Schist subduction complex, extends from the Orocopia Mountains (Calif.) southeastward through the Chocolate Mountains (parallel to the southern San Andreas fault). Where Highway 78 crosses the Chocolate Mountains (Fig. 1), the CMA turns eastward through the Black Mountain-Picacho area (Calif.) and Trigo Mountains (Ariz.) into southwest Arizona. It separates southernmost Bouse Formation outcrops of the Blythe basin from subsurface Bouse outcrops to the south in the Yuma area. South of Blythe basin the CMA is transected by the lower Colorado River along a circuitous path. Here we focus on the geology of an area between the central Chocolate Mountains and the Yuma Proving Grounds in Arizona. Specific landmarks include the southeast Chocolate Mountains, Midway Mountains, Peter Kane Mountain, Black Mountain, Picacho Peak, and Gavilan Hills. For simplicity, we refer to this as the eastern Chocolate Mountains.
Conference Paper↗
Evolution of Seismic Geyser, Yellowstone National Park
The most significant event that has affected the geyser basins of Yellowstone National Park since its discovery was the Hebgen Lake earthquake, which occurred at 11:37 PM on August 17, 1959, with a Richter magnitude of 7.1. The epicenter of this earthquake was just west of the park, about 48 km northwest of the Upper Geyser Basin. No earthquake of comparable intensity had jarred the geyser basins in historic times. More hydrothermal changes occurred in response to this disturbance than during the previous 90 years of the park's history. During the first few days after the earthquake, a reconnaissance was made of most of the thermal features in the Firehole River geyser basins (fig. 1). Early results showed that at least 289 springs had erupted as geysers, and, of these, 160 were springs with no previous record of eruption (Marler, 1964). Some previously obscure springs had erupted very powerfully, and large pieces of sinter were strewn about their craters.
Wyoming↗
Water quality and chemical evolution of ground water within the north coast limestone aquifers of Puerto Rico
Waters within the north coastal limestone aquifers are suitable for public supply, industrial and agricultural uses. For the artesian aquifer and the updip parts of the water table aquifer, calcium and bicarbonate are the dominant ionic species with total dissolved solids and chloride concentrations below 500 and 250 mg/L, respectively. In coastal areas of the water table aquifer, where a freshwater-saltwater mixing zone occurs, the calcium bicarbonate facie grade to a sodium-chloride facie. Within this zone, concentrations of total dissolved solids and chloride are greater than 250 and 500 mg/L respectively, affecting the suitability of the water for some uses. Geochemical models were constructed to determine the physical and chemical reasons for the prevailing water quality patterns of the north coast limestone aquifers . Models indicate that calcite and carbon dioxide dissolution, precipitation or degassing are the primary processes. The mixing of recharge water or saltwater with aquifer waters is an important feature within the water table aquifer. The models provide further evidence that support the circulation of groundwater within the north coast limestone.
Conference Paper↗
Sockeye salmon evolution, ecology, and management
This collection of articles and photographs gives managers a good idea of recent research into what the sockeye salmon is and does, covering such topics as the vulnerability and value of sockeye salmon ecotypes, their homing ability, using new technologies to monitor reproduction, DNA and a founder event in the Lake Clark sockeye salmon, marine-derived nutrients, the exploitation of large prey, dynamic lake spawning migrations by females, variability of sockeye salmon residence, expression profiling using cDNA microarray technology, learning from stable isotropic records of native otolith hatcheries, the amount of data needed to manage sockeye salmon and estimating salmon "escapement."
Scitech Book News↗
Latest Miocene-earliest Pliocene evolution of the ancestral Rio Grande at the Española-San Luis Basin boundary, northern New Mexico
We use stratigraphic relations, paleoflow data, and 40 Ar/ 39 Ar dating to interpret net aggradation, punctuated by at least two minor incisional events, along part of the upper ancestral Rio Grande fluvial system between 5.5 and 4.5 Ma (in northern New Mexico). The studied fluvial deposits, which we informally call the Sandlin unit of the Santa Fe Group, overlie a structural high between the San Luis and Española Basins. The Sandlin unit was deposited by two merging, west- to southwest-flowing, ancestral Rio Grande tributaries respectively sourced in the central Taos Mountains and southern Taos Mountains-northeastern Picuris Mountains. The river confluence progressively shifted southwestward (downstream) with time, and the integrated river (ancestral Rio Grande) flowed southwards into the Española Basin to merge with the ancestral Rio Chama. Just prior to the end of the Miocene, this fluvial system was incised in the southern part of the study area (resulting in an approximately 4–7 km wide paleovalley), and had sufficient competency to transport cobbles and boulders. Sometime between emplacement of two basalt flows dated at 5.54± 0.38 Ma and 4.82±0.20 Ma (groundmass 40 Ar/ 39 Ar ages), this fluvial system deposited 10–12 m of sandier sediment (lower Sandlin subunit) preserved in the northern part of this paleovalley. The fluvial system widened between 4.82±0.20 and 4.50±0.07 Ma, depositing coarse sand and fine gravel up to 14 km north of the present-day Rio Grande. This 10–25 m-thick sediment package (upper Sandlin unit) buried earlier south- to southeast-trending paleovalleys (500–800 m wide) inferred from aeromagnetic data. Two brief incisional events are recognized. The first was caused by the 4.82±0.20 Ma basalt flow impounding south-flowing paleodrainages, and the second occurred shortly after emplacement of a 4.69±0.09 Ma basalt flow in the northern study area. Drivers responsible for Sandlin unit aggradation may include climate-modulated hydrologic factors (i.e., variable sediment supply and water discharge) or a reduction of eastward tilt rates of the southern San Luis Basin half graben. If regional in extent, these phenomena could also have promoted fluvial spillover that occurred in the southern Albuquerque Basin at about 6–5 Ma, resulting in southward expansion of the Rio Grande to southern New Mexico.
New Mexico↗
Field guide to Laramide basin evolution and drilling activity in North Park and Middle Park, Colorado
Overview of the geologic history of the North Park–Middle Park area and its past and recent drilling activity. Field trip stops highlight basin formation and the consequences of geologic configuration on oil and gas plays and development. The starting point is the west flank of the Denver Basin to compare and contrast the latest Cretaceous through Eocene basin fill on both flanks of the Front Range, before exploring sediments of the same age in the North Park – Middle Park intermontane basin.
Colorado↗
Evolution of the Lower Tertiary Elko Lake Basin, a potential hydrocarbon source rock in Northeast Nevada
No abstract available.
Book chapter↗
Genetic diversity patterns and evolution of an aquatic rhabdovirus
No abstract available.
Conference Paper↗
Genetic variation and evolution of satellite viruses and satellite RNAs
No abstract available
Book chapter↗
Surficial deposits, weathering processes, and evolution of an inner Coastal Plain landscape, Augusta, Georgia
No abstract available.
Georgia↗
Geologic framework, evolution, and sediment resources for restoration of the Louisiana Coastal Zone
The Louisiana Coastal Zone along the north-central Gulf of Mexico represents one of America's most important coastal ecosystems in terms of natural resources, human infrastructure, and cultural heritage. This zone also has the highest rates of coastal erosion and wetland loss in the nation because of a complex combination of natural processes and anthropogenic activities during the past century. In response to the dramatic land loss, regional-scale restoration plans are being developed through a partnership of federal and state agencies. One objective is to maintain the barrier island and tidal inlet systems, thereby reducing the impact of storm surge and interior wetland loss. Proposed shore line restoration work relies primarily upon the use of large volumes of sand-rich sediment for shoreline stabilization and the implementation of the shoreline projects. Although sand-rich sediment is required for the Louisiana restoration projects, it is of limited availability within the generally clay to silt-rich, shallow strata of the Louisiana Coastal Zone. Locating volumetrically significant quantities of sand-rich sediment presents a challenge and requires detailed field investigations using direct sampling and geophysical sensing methods. Consequently, there is a fundamental need to thoroughly understand and map the distribution and textural character {e.g., sandiness) of sediment resources within the Coastal Zone for the most cost-effective design and completion of restoration projects.
Gulf of Mexico↗