Depth profiles in a tropical, volcanic critical zone observatory: Basse-Terre, Guadeloupe
No abstract available.
Basse-Terre, Lesser Antilles↗
SEARCH · Geology Reports
Results for “White Paper”
Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Late Cenozoic geology and lacustrine history of Searles Valley, Inyo and San Bernardino Counties, California
Searles Valley is an arid, closed basin lying 70 km east of the south end of the Sierra Nevada, California. It is bounded on the east and northeast by the Slate Range, on the west by the Argus Range and Spangler Hills, and on the south by the Lava Mountains; Searles (dry) Lake occupies the north-central part of the valley. During those parts of late Pliocene and Pleistocene time when precipitation and runoff from the east side of the Sierra Nevada into the Owens River were much greater than at present, a chain of as many as five large lakes was created, of which Searles Lake was third. The stratigraphic record left in Searles Valley when that lake expanded, contracted, or desiccated, is fully revealed by cores from beneath the surface of Searles (dry) Lake and partly recorded by sediments cropping out around the edge of the valley. The subsurface record is described elsewhere. This volume includes six geologic maps (scales: 1:50,000 and 1:10,000) and a text that describes the outcrop record, most of which represents sedimentation since 150 ka. Although this outcrop record is discontinuous, it provides evidence indicating the lake's water depths during each expansion, which the subsurface record does not. Maximum-depth lakes rose to the 2,280-ft (695 m) contour, the level of the spillway that led overflowing waters to Panamint Valley; that spillway is about 660 ft (200 m) above the present dry-lake surface. Several rock units of Tertiary and early Quaternary ages crop out in Searles Valley. Siltstone and sandstone of Tertiary age, mostly lacustrine in nature and locally deformed to near-vertical dips, are exposed in the southern part of the valley, as is the younger(?) upper Miocene Bedrock Spring Formation. Unnamed, mostly mafic volcanic rocks of probable Miocene or Pliocene age are exposed along the north and south edges of the basin. Slightly deformed lacustrine sandstones are mapped in the central-southwestern and southern parts of the study area. The Christmas Canyon Formation and deposits mapped as older gravel and older tufa are extensively exposed over much of the basin floor. The older gravel unit and the gravel facies of the Christmas Canyon Formation are boulder alluvial gravels; parts of these units are probably correlative. The lacustrine facies of the Christmas Canyon Formation includes the Lava Creek ash, which is dated at 0.64 Ma; the older tufa deposits may be equivalent in age to those sediments. Most of this study concerns sediments of the newly described Searles Lake Formation, whose deposition spanned the period between about 150 ka and 2 ka. Most of this formation is lacustrine in origin, but it includes interbedded alluvium. To extract as much geologic detail as possible, criteria were developed that permitted (1) intrabasin correlation of some thin outcrop units representative of only a few thousand years (or less), (2) identification of unconformities produced by subaerial erosion, (3) identification of unconformities produced by sublacustrine erosion, and (4) correlation of outcrop units with subsurface units. The Searles Lake Formation is divided into seven main units, many of which are subdivided on the five larger scale geologic maps. Units A (oldest), B, C, and D are dominantly lacustrine in origin. The Pleistocene-Holocene boundary is placed at the top of unit C. In areas that were a kilometer or more from shore at the time of deposition, deposits of units A,B, and C consist of fine, highly calcareous sand, silt, or clay; nearer to shore they consist of well-sorted coarse sand and gravel. Unit A has been locally subdivided into as many as four subunits, unit B into six subunits, and unit C into six subunits. The finer facies of units A, B, and C contain such high percentages of Caco3 that they are best described as marl. Sediments of unit C, and to a lesser extent those of unit B, are laminated with light- to white-colored layers of aragonite, calcite, or dolomite(?) that may repre
California↗
Hydrologic conditions near Glendo, Platte County, Wyoming
The Glendo area of Platte and Carbon Counties, Wyo., about 250 square miles in extent, is in the Great Plains physiographic province. It is bordered on the west by the Laramie Range and on the east by the Hartville uplift. The North Platte River and Horseshoe and Middle Bear Creeks are the principal streams that drain the area. Gentle to steep hills, which lie between 4,450 and 6,360 feet above sea level, characterize the topography. Approximately 7,600 acres of land is cultivated in the Horseshoe Creek valley and 1,000 or more acres in the Cassa Flats of the North Platte River and Middle Bear Creek valleys. The average annual precipitation of 13.15 inches and the streamflow diverted for irrigation from Horseshoe Creek and the North Platte River are usually inadequate to sustain crops during the entire growing season. Sedimentary rocks, which underlie about 99 percent of the Glendo area, range in age from Cambrian(?) to Recent and in thickness from about 3,000 to 4,700 feet. Beds of Paleozoic and Mesozoic age dip steeply away from the Laramie Range and the Hartville uplift to form a large syncline, which is interrupted by the Elkhorn anticline in the central part of the area. Beds of Tertiary and Quaternary age that were deposited over the older structural features and later were partly removed by erosion have dips of less than 6 ? . The 'Converse sand' of local usage at the top of the Hartville Formation of Mississippian(7), Pennsylvanian, and Permian age, the White River Formation of Oligocene age, and the flood-plain deposits of Recent .age are the most important aquifers in the Glendo area. The Hartville Formation consists predominantly of hard limestone and dolomite and of lesser amounts of sandstone and shale ; its thickness ranges from 850 to 1,050 feet throughout most of the area. The 'Converse sand' is an artesian aquifer consisting of fine- to medium-grained porous sandstone having an average thickness of about 80 feet. Recharge to the Hartville Formation is mainly from seepage of surface water from Glendo Reservoir and Spring Creek; ground water is discharged from the formation to the overlying White River Formation and the alluvium in the North Platte River valley near Cassa and to four wells in the Horseshoe Creek valley. Flowing wells yielding from a few gallons per minute to 175 gpm (gallons per minute) or more from the 'Converse sand' can probably be located in an area from ? mile to 1? miles wide and about 4? miles long in the lower Horseshoe Creek valley. The depth to the 'Converse sand' in this area depends upon the topographic relief and distance from the outcrop and ranges from 250 to about 1,000 feet. The discharge induced by pumping a well in the aquifer in the 'Converse sand' would probably amount to about 2 gpm per foot of drawdown. Values of 2,000, 2,100, and 10,300 gpd (gallons per day) per ft for the coefficient of transmissibility of the 'Converse sand' were obtained from aquifer tests at three wells. The chemical analyses of samples from the Hartville Formation ('Converse. sand' included) indicate that the water in the formation is of fairly good quality and adequate for domestic, stock, and irrigation uses, although the fluoride content is low and the water is hard. The White River Formation is composed of as much as 575 feet of fractured siltstone and claystone, and the flood-plain deposits include up to 65 feet of silt, sand, and gravel. Precipitation is the main type of recharge to the rocks of Tertiary age. Recharge to the alluvium in the valleys of Horseshoe Creek and the North Platte River occurs mainly by seepage of ground water from. underlying beds, by infiltration of irrigation water, and by infiltration of streamflow as bank storage. Ground water is discharged naturally from the area by seepage to streams, by underflow, and by evapotranspiration and artificially by wells. In 1961, the total discharge from 38 wells in the White River and Arikaree Formations and 2
Water Supply Paper↗
Miocene Total Petroleum System -- Southeast Stable Shelf Assessment Unit of the San Joaquin Basin Province: Chapter 13 in Petroleum systems and geologic assessment of oil and gas in the San Joaquin Basin Province, California
The confirmed stratigraphic and structural-stratigraphic Southeast Stable Shelf Assessment Unit (AU) of the Miocene Total Petroleum System (San Joaquin Basin Province) comprises all hydrocarbon accumulations within the geographic limits of the AU. Traps typically display low dip angles, gentle folds, and normal faults. Reservoirs, which range in age from fractured Mesozoic basement rocks to Holocene nonmarine rocks, are mainly Oligocene to Miocene sandstones from the uppermost slope and adjacent shelf of the San Joaquin Basin, shallow marine shelf sandstones mainly of Miocene age, and nonmarine sandstones and conglomerates mostly of Pliocene- Pleistocene age. Faults have relatively small vertical displacements. Map boundaries of the assessment unit are shown in figures 13.1 and 13.2; this assessment unit replaces the Southeast Stable Shelf play 1002 considered by the U.S. Geological Survey (USGS) in its 1995 National Assessment (Beyer, 1996). Stratigraphically, the AU extends from the uppermost crystalline basement to the topographic surface (fig. 13.3). The AU is bounded on the west by the approximate location of the shelfslope break of the San Joaquin Basin in late Miocene time, thus excluding reservoirs in the deep-water Stevens sand of Eckis (1940). The eastern boundary of the AU is the edge of onlap of Neogene sedimentary sequences on crystalline basement rocks of the Sierra Nevada. The northern AU boundary is placed at the approximate northern extent of oils in shelf-facies reservoirs known to be sourced by the Miocene Total Petroleum System. This northern boundary explicitly excludes the Deer Creek and Jasmin fields, which were included in the corresponding earlier (1995) USGS play (Beyer, 1996), but which are now known to contain oil generated from Eocene source rocks. The White Wolf Fault bounds the AU on the south.
California↗
Miocene Total Petroleum System -- Lower Bakersfield Arch Assessment Unit of the San Joaquin Basin Province: Chapter 14 in Petroleum systems and geologic assessment of oil and gas in the San Joaquin Basin Province, California
The Lower Bakersfield Arch Assessment Unit (AU) of the Miocene Total Petroleum System (San Joaquin Basin Province) is primarily defined by the distribution of hydrocarbons generated from biosiliceous shale of the Monterey Formation and by the distribution of basinal-facies sandstones of the Stevens sand of Eckis (1940; hereafter referred to as Stevens sand). Traps are principally stratigraphic and structural/stratigraphic, with most discovered accumulations occurring in deep-sea channel, fan, and braided submarine channel deposits of the late Miocene Stevens sand. Smaller and fewer accumulations are found in older sandstones such as the Vedder and Jewett Sands of Oligocene to Miocene age. Compared to the west side of the basin, the AU is largely unstructured, except for localized down-to-the-basin normal faults. Map boundaries of the assessment unit are shown in figures 14.1 and 14.2; this assessment unit supersedes the Lower Bakersfield Arch play 1003 considered by the U.S. Geological Survey (USGS) in the 1995 National Assessment (Beyer, 1996). Stratigraphically, the AU extends from the uppermost crystalline basement to the topographic surface (fig. 14.3). The AU is bounded on the east and north by the limit of basinal- facies sandstones of the Stevens sand; this eastern boundary corresponds to the approximate location of the shelf-slope break of the San Joaquin Basin in late Miocene time. The western boundary of the AU is the approximate eastern limit of structural deformation on the basin’s west side. The White Wolf Fault bounds the AU on the south.
California↗
The petrology of dispersed organic matter in sedimentary rocks: Review and update
Organic petrology developed from coal petrology, and, in the 1960s, it began to be applied to the study of dispersed organic matter (DOM) in sedimentary rocks other than coal. Over the last few decades, the petrology of DOM has been used to characterize organic matter in sedimentary basins with an emphasis on fossil fuel resource exploration. Today, due to the global research shift on topics related to climate, organic petrology has expanded into new application areas, such as geothermal exploration, biological carbon storage (biochar), disposal, and management of radioactive waste. From the publication of the International Handbook of Coal Petrology (mid-20th century) to the present day, a large number of standards, books, and articles have been published as a result of the work of organic petrographers and petrologists around the world and efforts of the International Committee for Coal and Organic Petrology (ICCP) and The Society for Organic Petrology (TSOP) to promote the study of organic petrology. The current fundamentals and standards of organic petrology provide the international scientific community with well-informed guidance and recommendations to promote in-depth research. However, this information is currently widely scattered, leading to discrepancies in methodology and terminology. Therefore, this paper aims to present a comprehensive review of the main analytical standard test methods and techniques currently used in the petrology of DOM under reflected white light and UV and blue-light excitation, and to provide an efficient and well-defined reference guide. Furthermore, considering the important role of the ICCP in the development of organic petrology since the 1950s, a brief review of the ongoing activities of ICCP dealing with DOM is also presented.
International Journal of Coal Geology↗
Revised Cretaceous and Tertiary stratigraphic nomenclature in the Colville Basin, Northern Alaska
A revised stratigraphic nomenclature is proposed for Cretaceous and Tertiary geologic units of the central and western North Slope of Alaska. This revised nomenclature is a simplified and broadly applicable scheme suitable for a suite of digital geologic quadrangle maps being prepared jointly by the U.S. Geological Survey and the Alaska Department of Natural Resources, Division of Geological and Geophysical Surveys and Division of Oil and Gas. This revised nomenclature scheme is a simplification of a complex stratigraphic terminology that developed piecemeal during five decades of geologic investigations of the North Slope. It is based on helicopter-supported geologic field investigations incorporating information from high-resolution aerial photography, satellite imagery, paleontology, reflection seismic records, and sequence stratigraphic concepts. This revised nomenclature proposes the abandonment of the Colville Group; demotion of the Nanushuk Group to formation status; abandonment of six formations (Kukpowruk, Tuktu, Grandstand, Corwin, Chandler, and Ninuluk); revision of four formations (Sagavanirktok, Prince Creek, Schrader Bluff, and Seabee); elevation of the Tuluvak Tongue of the Prince Creek Formation to formation status; revision of two members (Franklin Bluffs Member and Sagwon Member of the Sagavanirktok Formation); abandonment of eight members or tongues (Kogosukruk, Rogers Creek, Barrow Trail, Sentinel Hill, Ayiyak, Shale Wall, Niakogon, and Killik); and definition of one new member (White Hills Member of the Sagavanirktok Formation).
Professional Paper↗
Application of frequency- and time-domain electromagnetic surveys to characterize hydrostratigraphy and landfill construction at the Amargosa Desert Research Site, Beatty, Nevada
In 2014 and 2015, the U.S. Geological Survey (USGS), conducted frequency-domain electromagnetic (FDEM) surveys at the USGS Amargosa Desert Research Site (ADRS), approximately 17 kilometers (km) south of Beatty, Nevada. The FDEM surveys were conducted within and adjacent to a closed low-level radioactive waste disposal site located at the ADRS. FDEM surveys were conducted on a grid of north-south and east-west profiles to assess the locations and boundaries of historically recorded waste-disposal trenches. In 2015, the USGS conducted time-domain (TDEM) soundings along a profile adjacent to the disposal site (landfill) in cooperation with the U.S. Environmental Protection Agency (USEPA), to assess the thickness and characteristics of the underlying deep unsaturated zone, and the hydrostratigraphy of the underlying saturated zone. FDEM survey results indicate the general location and extent of the waste-disposal trenches and reveal potential differences in material properties and the type and concentration of waste in several areas of the landfill. The TDEM surveys provide information on the underlying hydrostratigraphy and characteristics of the unsaturated zone that inform the site conceptual model and support an improved understanding of the hydrostratigraphic framework. Additional work is needed to interpret the TDEM results in the context of the local and regional structural geology.
Nevada↗
Ecosystem dynamics of the Northern Rocky Mountains, USA
Explore the source record for details and available documents.
Conference Paper↗
Atlantic white cedar plantings in St. Tammany Parish, Louisiana, and the Bogue Chitto National Wildlife Refuge, Mississippi
Populations of Atlantic white cedar (Chamaecyparis thyoides (L.) B.S.P.) growing at the extreme western range of the species are in danger of being lost, and information on the ecology of these populations is limited. Seeds and seedlings ("wildlings") were collected near Vancleave, MS. The wildlings were transplanted to bay-head sites on Bogue Chitto National Wildlife Refuge where canopy gaps had been created in early 1989. Seeds were germinated, grown in a greenhouse, and transplanted a year later to three locations within a slash pine plantation: a bedded and fertilized site, the margin of a cypress pond, and a wet gap, in St. Tammany Parish, Lousiana. These plantings were established to study survival and growth in different habitat types, to compare seedlings grown from seed versus transplanted wildlings, and to attempt to generate some interest in planting Atlantic white-cedar in the extreme western portion of its natural range. Overall seedling survival averaged 94 percent after five growing seasons, although significant differences were detected among sites. Mean height per site in 1994 was significantly greater at the bedded and fertilized site (233 centimeters), and lowest at the slash pine site (91 centimeters). Growth at the cypress pond site was intermediate (158 centimeters). Wildlings at the bay-head sites had lower survival rates (75 and 64 percent), but average heights for the two sites were similar to those of the seedlings (265 and 165 centimeters). These results show that plantings involving either local seed or wildlings are viable choices for regenerating Atlantic white-cedar in southern Mississippi and eastern Louisiana.
Louisiana; Mississippi↗
A massive kill of white perch (Roccus americanus) involving a Pasteurella-like bacterium
No abstract available at this time.
Conference Paper↗
Fitting statistical distributions to sea duck count data: implications for survey design and abundance estimation
Determining appropriate statistical distributions for modeling animal count data is important for accurate estimation of abundance, distribution, and trends. In the case of sea ducks along the U.S. Atlantic coast, managers want to estimate local and regional abundance to detect and track population declines, to define areas of high and low use, and to predict the impact of future habitat change on populations. In this paper, we used a modified marked point process to model survey data that recorded flock sizes of Common eiders, Long-tailed ducks, and Black, Surf, and White-winged scoters. The data come from an experimental aerial survey, conducted by the United States Fish & Wildlife Service (USFWS) Division of Migratory Bird Management, during which east-west transects were flown along the Atlantic Coast from Maine to Florida during the winters of 2009–2011. To model the number of flocks per transect (the points), we compared the fit of four statistical distributions (zero-inflated Poisson, zero-inflated geometric, zero-inflated negative binomial and negative binomial) to data on the number of species-specific sea duck flocks that were recorded for each transect flown. To model the flock sizes (the marks), we compared the fit of flock size data for each species to seven statistical distributions: positive Poisson, positive negative binomial, positive geometric, logarithmic, discretized lognormal, zeta and Yule–Simon. Akaike’s Information Criterion and Vuong’s closeness tests indicated that the negative binomial and discretized lognormal were the best distributions for all species for the points and marks, respectively. These findings have important implications for estimating sea duck abundances as the discretized lognormal is a more skewed distribution than the Poisson and negative binomial, which are frequently used to model avian counts; the lognormal is also less heavy-tailed than the power law distributions (e.g., zeta and Yule–Simon), which are becoming increasingly popular for group size modeling. Choosing appropriate statistical distributions for modeling flock size data is fundamental to accurately estimating population summaries, determining required survey effort, and assessing and propagating uncertainty through decision-making processes.
Statistical Methodology↗
Benefits of genetic data for the design of Brook Trout translocation efforts
With wild trout populations in decline, many conservation practitioners are evaluating the feasibility of incorporating reintroduction and genetic rescue into management frameworks. As interest in these conservation tools continues to grow, so too has the need for rigorous science to evaluate translocation success and improve the efficacy of future efforts. From this, it has become increasingly apparent that approaches which consider both demographics and genetics are most likely to result in successful translocations. In particular, while demographic data are often a central component of project designs, they are insufficient for diagnosing genetic threats such as low diversity, maladaptation, and introgression that characterize many wild trout populations. Consideration for these genetic characteristics is important for long-term project success and to reduce the unintended spread of domestic lineages across the landscape. Using a case study of reintroduction of Brook Trout Salvelinus fontinalis into a North Carolina stream, we show how a combined demographic and genetic approach can be used throughout all stages of project design. In particular, we highlight how genetic data were informative for identifying source populations that had the greatest potential to establish a population with the genetic diversity needed for future adaptation. We also discuss how genetic monitoring of the reintroduced population provided insights into reproductive success and genetic diversity that could be indicative of long-term population persistence. While monitoring is ongoing, this combined genetic and demographic approach provides a promising framework for helping meet reintroduction goals and provides more opportunities for adaptive management following translocation.
Conference Paper↗
Chemical weathering of a marine terrace chronosequence, Santa Cruz, California: Deciphering reaction rates from mineral depth profiles
A soil chronosequence developed on marine terraces along coastal California, exhibits deeper and more intensively weathered mineral profiles with increasing age (65 to 226 kyrs). Feldspar concentrations generally increase linearly with terrace depth. The slope or weathering gradient is defined by the ratio of the weathering rate and the velocity at which the profile penetrates into the regolith.A spread sheet calculator further refines profile geometries, demonstrating that the non-linear regions at low residual feldspar concentrations are dominated by exponential changes in mineral surface to volume and at high residual feldspar concentrations by the approach to thermodynamic saturation.These parameters, in addition to the kinetic rate constant, are of secondary importance to the fluid flux qh which controls the weathering velocity and solute fluxes from the profile. © 2007 Taylor & Francis Group, London.
California↗
Organochlorine residues and eggshell thinning in anhingas and waders
Residues of organochlorine compounds occur commonly in environmental samples and have been associated with adverse effects in numerous avian species (Cooke 1973; L. F. Stickel 1973; W. H. Stickel 1975; Ohlendorf et al. 1977; H. M. Ohlendorf, R. W. Risebrough, and K. Vermeer, unpublished manuscript). The affected species are usually terminal consumers, generally those feeding on aquatic organisms (primarily fish) or birds. Brown Pelicans ( Pelecanus occidentalis ), Double-crested Cormorants (Phalacrocorax auritus) , and certain herons are among the species that have exhibited shell thinning in some regions (see Ohlendorf et al. 1977 for review). In 1972, we began a study to determine: (1) geographic differences in the occurrence of environmental pollutants in Anhingas ( Anhinga anhinga ) and waders in the eastern United States; (2) differences in environmental pollutant levels among those species nesting at the same localities; and (3) whether eggshell thickness had changed since the widespread use of organochlorine pesticides began in the mid-1940's. The wader species included in our study were: Great Blue Heron ( Ardea herodias ), Green Heron ( Butorides virescens ), Little Blue Heron ( Florida caerulea ), Cattle Egret ( Bubulcus ibis ), Reddish Egret ( Dichromanassa rufescens ), Great Egret ( Casmerodius albus ), Snowy Egret ( Egretta thula ), Louisiana Heron ( Hydranassa tricolor ), Black-crowned Night Heron ( Nycticorax nycticorax ), Yellow-crowned Night Heron ( Nyctanassa violacea ), Least Bittern ( Ixobrychus exilis ), American Bittern ( Botaurus lentiginosus ), Wood Stork ( Mycteria americana ), Glossy Ibis ( Plegadis falcinellus ), White Ibis ( Eudocimus albus ), and Roseate Spoonbill ( Ajaia ajaja ).
Conference Paper↗
Silver-bearing black calcite in western mining districts
The name black calcite has been applied from time to time to a dark gray to black variety of calcite or aragonite in metalliferous ore deposits in the Western States. Most of the material shows curved, roughly rhombic cleavage. The color is due to dispersed minute grains of one or more oxides of manganese, so dispersed that they rarely show any relation to cleavage surfaces or outward crystal forms.Recent study shows that the black calcite from numerous metalliferous deposits in the Western States contains small amounts of several metals, especially zinc, lead, and silver; in places, the crude black calcite contains as much as one percent silver and the black residue remaining after solution of the calcite as much as 1,500 ounces of silver to the ton. Black calcite is recognized in some deposits of Late Cretaceous to early Tertiary age where the host is Paleozoic carbonate rocks; thus far, this variety contains the larger amounts of silver. It is also present in some vein deposits where the host is generally volcanic rocks of middle Tertiary age; these are known in many districts in the southwest and even though the lead and zinc content is noteworthy, the silver content rarely exceeds one ounce to the ton (8).By studying polished sections of black calcite from the Aurora mine, White Pine County, Nevada, three silver-bearing manganate minerals have been recognized; (1) an argentian chalcophanite containing 7.5 percent silver (Ag 2 O), to which, in a following paper, the name aurorite is given; (2) argentian todorokite containing 3.9 percent silver (Ag 2 O), and (3) hydrous silver-bearing lead manganese oxide, containing 1.18 percent silver (Ag 2 O).
Nevada↗
Tectonically controlled fan delta and submarine fan sedimentation of late Miocene age, southern Temblor Range, California
The Santa Margarita Formation in the southern Temblor Range, composed of conglomerate and subordinate sandstone, evolved as a large complex of fan deltas and submarine fans in late Miocene time. An 80 to 90-m.y.-old granitic basement of the Salinian block and an accompanying 23.5-m.y.-old volcanic field now located in the northern Gabilan Range and the Pinnacles area, respectively, were the primary source terranes. In general, the fan deltas crop out along the west side of the southern Temblor Range, whereas the proximal parts of the submarine fans crop out along the east side of the range. The fan deltas consist of subaerial topset beds and low-angle basinward-dipping subaqueous foreset beds. Strata interpreted to be topset beds are composed largely of conglomerate with thick to very thick horizontal beds and matrix-supported clasts. Most of the thick to very thick conglomerate beds are internally massive and disorganized. Strata interpreted as foreset beds are composed of thick-bedded, large-scale, low-angle, cross-stratified conglomerate and sandstone units which commonly are internally massive. Abundant molluskan macrofossils such as Ostrea and Pecten are present in the subaqueous foreset beds; many have been displaced downslope from their original site of deposition. Conglomerate- and sandstone-filled submarine canyons, through which coarse-grained detritus was transported to the adjacent submarine fans, locally have cut into the foreset beds of the fan deltas. These submarine canyon deposits are generally better stratified than adjacent foreset-bed deposits, and they consist of thick horizontal beds, internally massive or normally graded, arranged in fining- and thinning-upward sequences. Isolated and composite conglomerate- and sandstone-filled channels, which crop out on the east flank of the southern Temblor Range, are interpreted as proximal submarine-fan channel deposits. These channel-form conglomerate and sandstone deposits are characterized by thick, horizontal beds which are internally massive or normally graded containing division T a , and locally T b , of the Bouma sequence. Sparse calcareous foraminifers collected from diatomaceous interbeds suggest that these fan channels were deposited in upper bathyal water depths. Subaerial and regenerated subaqueous debris flows probably formed the bulk of the Santa Margarita fan delta and submarine fan system. Santa Margarita debris flows ranged from the mudflow variety to the cataclysmic debris-avalanche variety. The cogenetic Republic and Williams sandstones of local usage, located on the east side of the southern Temblor Range, are slightly older and finer grained than the Santa Margarita Formation. These units, containing well-graded sandstones, fining- and thinning-upward and coarsening- and thickening-upward sandstone sequences, thick-bedded tabular and channel-shaped sandstones, a mixture of shallow- and deep-water foraminifers, and a fan-shaped geometry in the subsurface, are interpreted as submarine fan deposits. Sedimentation associated with the Santa Margarita Formation was intimately related to the growing southern Temblor Range anticlinorium and the right-laterally shifting Salinian block along the San Andreas fault. Examples of control exerted on Santa Margarita sedimentation by the southern Temblor Range anticlinorium include the preferential accumulation of sediments along the flanks of the anticlinorium, thickening of strata on the downthrown side of the Recruit Pass fault and on flanks of selected anticlines, intraformational unconformities, and possible partial blockage of the eastward-prograding fan deltas by the Recruit Pass fault. East of the growing southern Temblor Range anticlinorium, the distal ends of the Santa Margarita submarine fans were deflected northwestward by the growing Buena Vista Hills anticline. Several examples of well-defined diachronous sedimentation, where conglomerates and sandstones of the Santa Margarita Formation occupy progressively higher stratigraphic levels in a northwest direction subparallel to the trace of the San Andreas fault, strongly imply that the Salinian basement terrane was shifting in a right-lateral sense during Santa Margarita sedimentation. Regional factors of importance in focusing conglomerate sedimentation on the southern Temblor Range locale for a 2- to 3-m.y. period in the late Mohnian were right-lateral oblique slip on the San Andreas fault, formation of the "big bend" in the San Andreas fault by left-lateral slip along the Garlock and White Wolf faults, and the partial overlap of the Salinian and Franciscan assemblage basement rocks.
California↗