Geology topics
Research about San Diego County, California
Source-linked reports with geographic coverage including San Diego County, California.
Habitat characteristics and nest success of snowy plovers associated with California least tern colonies
Nest success of Snowy Plovers ( Charadrius alexandrinus ) was estimated at six sites in San Diego County, California, to determine the effects of habitat characteristics and social factors on predation risk. Egg predation was expected to be lower for plovers nesting among Least Terns ( Sterna antillarum ) because of benefits associated with nesting under the “protective umbrella” of a colonial species. Snowy Plovers nested adjacent to objects and in areas with more vegetation cover than random sites in beach and fill habitats and in areas with more debris cover in beach and salt pan habitats. Estimated nest success from 1994–1997 was 50%, and most predation was attributed to corvids, primarily Common Ravens ( Corvus corax ). Social factors, including distance to nearest Least Tern and Snowy Plover nests, predicted nest success whereas habitat characteristics did not. Nest success was greatest for plovers nesting closest to an active tern nest and nesting at intermediate distances to conspecifics. Nest success also varied among years and sites, with two sites consistently less successful over the four years. Nests within tern colonies received some mitigation of egg predation. Plover nests initiated prior to the arrival of Least Terns were less likely to hatch eggs than later nests; nevertheless, Snowy Plovers in southern California initiated nesting well before Least Terns.
Contaminants in eggs of western snowy plovers and California least terns: Is there a link to population decline?
No abstract available.
Hydraulic properties of a fractured-rock aquifer, Lee Valley, San Diego County, California
No abstract available.
Nesting habitat of Belding’s Savannah sparrows in coastal salt marshes
Although the Belding’s Savannah sparrow ( Passerculus sandwichensis beldingl ) is listed as endangered in California, little is known about the factors that affect its abundance and distribution. Numbers of breeding pairs, nesting territory sizes, and vegetation characteristics were measured at fourteen study plots in two southern California coastal wetlands, Tijuana Estuary and Los Peñasquitos Lagoon. Sparrows nested in middle salt marsh habitat in areas of dense pickleweed ( Salicornia virginica ) or saltgrass ( Distichlis spicata ). No nesting territories were found in transitional upland or low marsh habitat. Territory sizes were highly variable and significantly larger at Tijuana Estuary. Territory size may be related to nest site availability and water levels at time of establishment. More research is needed on the effects of habitat quality on reproductive success and territory size.
Water resources of Soledad, Poway, and Moosa basins, San Diego County, California
Reclaimed water is being considered as as supplemental water supply in the Soledad, Poway, and Moosa basins, San Diego County. This report describes the geology, soils, hydrology, and cultural factors in each of the basins as they relate to use of reclaimed water. Imported water is currently the major water-supply source in the basins. Groundwater supplies are used to a limited extent for both agricultural and domestic needs. Surface water flows are intermittent and, therefore, have not been developed for use in the basins. All three of the basins have the potential for use of reclaimed water, but only the Moosa basin is currently implementing a plan for such use. Concentrations of dissolved solids, chloride, and sulfate in both ground and surface water commonly exceed local basin objectives. As of 1985, plans for use of reclaimed water are oriented toward improving the quality of the groundwater.
Marine terrace deformation, San Diego County, California
The NW—SE trending southern California coastline between the Palos Verdes Peninsula and San Diego roughly parallels the southern part and off-shore extension of the dominantly right-lateral, strike-slip, Newport—Inglewood fault zone. Emergent marine terraces between Newport Bay and San Diego record general uplift and gentle warping on the northeast side of the fault zone throughout Pleistocene time. Marine terraces on Soledad Mt. and Point Loma record local differential uplift (maximum 0.17 m/ka) during middle to late Pleistocene time on the southwest side of the fault (Rose Canyon fault) near San Diego. The broad Linda Vista Mesa (elev. 70–120 m) in the central part of coastal San Diego County, previously thought to be a single, relatively undeformed marine terrace of Plio—Pleistocene age, is a series of marine terraces and associated beach ridges most likely formed during sea-level highstands throughout Pleistocene time. The elevations of the terraces in this sequence gradually increase northwestward to the vicinity of San Onofre, indicating minor differential uplift along the central and northern San Diego coast during Pleistocene time. The highest, oldest terraces in the sequence are obliterated by erosional dissection to the northwest where uplift is greatest. Broad, closely spaced (vertically) terraces with extensive beach ridges were the dominant Pleistocene coastal landforms in central San Diego County where the coastal slope is less than 1% and uplift is lowest. The beach ridges die out to the northwest as the broad low terraces grade laterally into narrower, higher, and more widely spaced (vertically) terraces on the high bluffs above San Onofre where the coastal slope is 20–30% and uplift is greatest. At San Onofre the terraces slope progressively more steeply toward the ocean with increasing elevation, indicating continuous southwest tilt accompanying uplift from middle to late Pleistocene time. This southwest tilt is also recorded in the asymmetrical valleys of major local streams where strath terraces occur only on the northeast side of NW—SE-trending valley segments. The deformational pattern (progressively greater uplift to the northwest with slight southwest tilt) recorded in the marine and strath terraces of central and northern coastal San Diego County conforms well with the historic pattern derived by others from geodetic data. It is not known how much of the Santa Ana structural block (between the Newport—Inglewood and the Elsinore fault zones) is affected by this deformational pattern.
Energy allocation patterns of a sprouting and nonsprouting species of Arctostaphylos in the California chaparral
The r- and K-selection theory was used to generate testable hypotheses about patterns of energy allocation in two chaparral shrubs of different reproductive strategies. Terminal-branchlet vegetative and reproductive biomass of the nonsprouting Arctostaphylos glauca and the sprouting A. glandulosa were sampled in a 23-year-old and a 90-year-old stand of chaparral to test the predictions that: (1) the terminal vegetative growth (g dry weight/m 2 of areal coverage) would be equal in the two species, in both stands; (2) oven dry weight (g) of reproductive parts/m 2 of areal coverage would be greater in A. glauca than in A. glandulosa in both aged populations; (3) allocation to reproductive parts by the shrubs in the 23-year-old stand would be greater than (or equal to) that of the 90-year-old shrubs. The amount of terminal vegetative growth was equal for both species in the 23-year-old and the 90-year-old stands. There was no statistically significant difference in the weight of fruits produced by the two species in the 23-year-old stand. However, fruit production by A. glauca was significantly greater than by A. glandulosa in the 90-year-old stand. Fruit production was also significantly greater for the older A. glauca shrubs than for those in the 23-year-old stand. The relationships of rainfall pattern and age of shrubs to fruit production are discussed.
Geologic map of Cuyamaca Peak 7 1/2' quadrangle, San Diego County, California
No abstract available.
Geologic map of Agua Caliente Springs quadrangle, San Diego County, California
No abstract available.
Differential seed predation on two species of Arctostaphylos (Ericaceae)
The fire-prone California chaparral contains two sympatric species of shrubs: Arctostaphylos glauca and A. glandulosa . A previous study showed that in a stand where both species had similar amounts of coverage, A. glauca had fewer seeds in the soil. We attempt to answer the questions: 1) Could ground-foraging seed predators produce the lower population of A. glauca seeds in the soil? 2) Do predators select fruits randomly with respect to fruit size? 3) Do the fruits of the two species differ in the proportions of fruit components (i.e. seeds, endocarp, mesocarp, and exocarp) in ways that could be important to seed predators? Predation was measured on artificial caches of fruits, for 17 weeks. Selection by predators was examined by comparing weights of fruits recovered from soil samples with newlymatured fruits on the shrubs. Fruits components were characterized by dividing fruits into 3 fractions and weighing. More fruits of A. glauca were removed from the caches. Fruits of both species recovered from the soil were lighter than those on the shrubs. The weights of seeds, stony and fleshy fruit layers were all larger in A. glauca . Within fruits of A. glandulosa , the weights of the three components, various combinations, and ratios were all significantly correlated, while in A. glauca no other component, combination of components, or ratio examined was significantly correlated with the weights of the seeds.
Hydrologic- and salt-balance investigations utilizing digital models Lower San Luis Rey River area, San Diego County, California
The Joint Administration Committee of the Santa Margarita and San Luis Rey Watershed Planning Agencies was designated as the agency to conduct studies leading to the development of a comprehensive water-quality management plan for the two watersheds. Hydrologic and salt balances for the Pauma, Pala, Bonsall, and Mission ground-water basins in the San Luis Rey River valley needed to develop the plan were difficult to compute because of the lack of data. Hydrologic models constructed and verified for 1958-72 for Pauma and Pala basins and for 1946-72 for Bonsall and Mission basins were beneficial in developing the hydrologic balances. Inflow and outflow to the basins used in model verification were consistent with known physical and hydrologic characteristics of the basins.
Geology and nickel mineralization of the Julian-Cuyamaca area, San Diego County, California
The Julian-Cuyamaca area is in the San Diego Mountains, one of the Peninsular Ranges of southern California. It lies in San Diego County, about 3 miles south of Julian, and approximately 60 miles northeast of San Diego. The area was mapped, and its nickel mineralization studied, from March to June, 1944; the work was part of the U. S. Geological Survey's program of strategic mineral investigations.
Geology and ground waters of the western part of San Diego County, California
No abstract available.
Notes on the geology of Carrizo Mountain and vicinity, San Diego County, Cal.
Through the courtesy of Dr. J. C. Merriam, of the University of California, and Dr. Stephen Bowers, of Los Angeles, small collections of fossil corals and mollusks from the vicinity of Carrizo Mountain, San Diego County, Cal., were sent to Dr. T. Wayland Vaughan and Dr. Ralph Arnold, of the U.S. Geological Survey, during the autumn of 1903. The material in these collections proved to be of exceptional interest to the paleontologists, and in order that a larger amount might be obtained for study and more definite information secured about the geology of the region, Dr. Bowers and the writer visited the field during the latter part of January, 1904.