The Rio Dell Formation: a Plio-Pleistocene basin slope deposit in Northern California     

DAVID J. W. PIPER  WILLIAM R. NORMARK  JAMES C. INGLE  JR 《Sedimentology》1976,23(3):309-328

The Rio Dell Formation (Pleistocene and Pliocene), exposed south of Eureka, California, is a prograded sequence of basinal turbidites overlain by basin slope and shelf deposits. The slope deposits studied in the Centerville Beach section accumulated in a steadily shallowing environment delineated by analysis of palaeobathymetrically significant benthonic foraminiferal biofacies in turn suggesting deposition at depths of 1000–100 m. Lower slope deposits interfinger with basinal turbidites derived from the Eel River delta to the north. Slumped blocks of silty mudstone, and associated silt and mud beds, are common. The middle slope deposits are mudstones; coarser sediments bypassed this zone. Mudstones and muddy siltstones alternate on the upper slope. Shallow depressions, probably slump scars, that have been rapidly filled by upper slope sediment are common. The transition to shelf deposits is marked by an increase in sediment grain size, in the degree of oxidation, and in the abundance of megafossils. High percentages of benthonic foraminifera displaced from shelf depths indicate that resedimentation processes are most important on the upper slope.  相似文献   

TEXTURAL DIFFERENTIATION ON THE SHORE FACE DURING EROSIONAL RETREAT OF AN UNCONSOLIDATED COAST, CAPE HENRY TO CAPE HATTERAS, WESTERN NORTH ATLANTIC SHELF     

DONALD J. P. SWIFT  ROBERT B. SANFORD  CHARLES E. DILL JR  NICHOLAS F. AVIGNONE 《Sedimentology》1971,16(3-4):221-250

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Oxygen and Carbon Isotope Studies of Contact Metamorphism of Carbonate Rocks     

SHIEH  Y. N.; TAYLOR  H. P.  JR. 《Journal of Petrology》1969,10(2):307-331

O¹⁸/O¹⁶ and C¹²/C¹³ ratios have been determined for carbonaterocks and coexisting minerals from two contact metamorphic aureolesat Birch Creek, California and Marble Canyon, Texas. The peliticmetasediments and granitic intrusions of the Birth Creek localitywere also analyzed for their O¹⁸/¹⁶ and D/H ratios. Oxygen andcarbon isotope fractionations in coexisting dolomite and calciteare interrelated but show no obvious correlation with sampledistance from the intrusive contact. Small-scale oxygen isotopicexchange effects between rock units are observed within a fewfeet of the intrusive-country rock contacts and the marble-schistcontacts at Birch Creek. Oxygen isotopic temperatures obtainedfrom quartz—biotite fractionations in the biotite schistsof Birch Creek show a systematic decrease with increasing distanceaway from the intrusive contact; the isotopic contact temperatureis calculated to be 535–45°C. Low O¹⁸/¹⁶ and C¹³/¹²ratiosof the contact metamorphic marbles generally correlate wellwith presence of calc-silicate minerals, indicating that theCO₂ liberated during metamorphic decarbonation reactions isenriched in both O¹⁸and C¹² relative to the carbonates. Materialbalance calculations indicate that the liberated CO₂ is about5 per mille richer in O¹⁸ and about 6 per mille richer in C¹³than coexisting calcite.  相似文献   

Size Selective Predation by the Asteroid Pisaster ochraceus on the Bivalve Mytilus calif ornianus: A Cost-Benefit Analysis     

James B.  Mcclintock Truman J.  Robnett JR. 《Marine Ecology》1986,7(4):321-332

Abstract. When simultaneously presented with equal numbers of four sizes of clumped Mytilus californianus (20, 35, 55 and 85 mm shell length), Pisaster ochraceus (arm length of 70-110mm R) showed a preference for the medium sizes (35 and 55mm length). Prey-size preference was positively correlated with predator size. Mean prey-digestion times (insertion of the stomach, opening of the valves and digestive period) decreased significantly following fiiing of an artificial gape between the valves of mussels. When presented with different sizes of clumped filed mussels, starfish still chose medium mussels, indicating that stomach insertion, valve opening, and digestion rate may not be important constraints determining size selective predation. Measurements of the force required to dislodge mussels from the substratum and conspecifics showed an increasing exponential relationship with mussel size. Size selective feeding may be an energy maximizing and time minimizing strategy, where energy gained from choosing larger mussels is balanced against disproportionately increased costs in energy and time of removing large mussels from the substratum.  相似文献   

Turbulent transport and heating in the auroral plasma of the topside ionosphere     

J.A. Ionson  R.S.B. Ong  E.G. Fontheim 《Planetary and Space Science》1979,27(2):203-210

Using plasma parameters from a typical stormtime ionospheric energy balance model, we have investigated the effects of plasma turbulence on the auroral magnetoplasma. The turbulence is assumed to be comprised of electrostatic ion cyclotron waves. These waves have been driven to a nonthermal level by a geomagnetic field-aligned, current-driven instability. The evolution of this instability is shown to proceed in two stages and indicates an anomalous increase in field-aligned electrical resistivity and cross-field ion thermal conductivity as well as a decrease in electron thermal conductivity along the geomagnetic field. In addition, this turbulence heats ions perpendicular to the geomagnetic field and hence leads to a significant ion temperature anisotropy.  相似文献   

Environmental and socioeconomic dynamics of the Indian Ocean tsunami in Penang,Malaysia     

Benjamin Horton  Michael Bird  Thomas Birkland  Susan Cowie  Ong Jin Eong  Andrea Hawkes  Gong Wooi Khoon  Lisa Law  Colin Macgregor  Aileen Tan Shau‐Hwai  Teh Tiong Sa  Zulfigar Yasin 《Singapore journal of tropical geography》2008,29(3):307-324

This paper addresses some of the environmental and socioeconomic dimensions of the 2004 Indian Ocean tsunami on Penang, Malaysia. We aim to offer wide access to unique and perishable data, while at the same time providing insight to ongoing debates about hazards, vulnerability and social capital. Our social survey examines some of the dynamics that shaped the tsunami impact, response and recovery process. While in terms of lives lost Penang may not conform to arguments surrounding vulnerable environments, the recovery process is more marked by social disparities in terms of the ability to access resources. Our physical survey records local topography, flow depth and flow direction, and charts the differential impact of the tsunami. Yet measuring hazards is not a straightforward process, and relies on reflexive methodologies and eyewitness accounts.  相似文献   

Scales of exception: Experiments with knowledge and sheer life in tropical Southeast Asia   总被引：1，自引：0，他引：1  

Aihwa Ong 《Singapore journal of tropical geography》2008,29(2):117-129

New political spaces, I suggest, are generated by varied strategies that govern populations in and through multiple scales of exception. I identify biopolitical assemblages as a space of inquiry into the situated play of exceptions that territorializes different kinds of value. Scales of exception are produced when a neoliberal logic of economic growth articulates biopolitical problems of population security. Neoliberal and biopolitical decisions not only focus on accumulating values in space, but also anticipate the value of currently devalued spaces. By invoking exceptions, states alternately favour neoliberal or biopolitical values, thus investing spaces with different kinds of value. The interplay of biopolitical and neoliberal logics and the resulting configuration of scales of exception are well illustrated in Southeast Asia in an age of pandemics. In Singapore, a technomedical hub assembles networks for capturing knowledge capital and property rights, configuring an ecology of expertise. This is a site of scientific prowess in a region increasingly viewed as a space of 'third world' exception to global health norms. In Indonesia, health crises have prompted a logic of ethical sensibility to basic human survival whereby political leaders invoke bio-sovereignty, configuring a national scale of ethical exception that challenges the global power of biocapital and the World Health Organization over the supply of vaccines. In contrast to approaches that foreground spaces of capital accumulation, I attend to diverse logics that differently valorize scales of exception, thus giving visibility to situated mechanisms that animate and mutate political cartography.  相似文献   

Random wave-induced onshore scour characteristics around submerged breakwaters using a stochastic method     

Dag Myrhaug  Muk Chen Ong 《Ocean Engineering》2010,37(13):1233-1238

This paper provides a stochastic method by which the two-dimensional onshore scour characteristics along the base of submerged breakwaters exposed to normally incident random waves on both sloping and horizontal sandy seabed can be derived. Here the formulas for the regular wave-induced scour characteristics provided by Young and Testik (2009) are used. These formulas are combined with describing the waves as a stationary Gaussian narrow-band random process to derive the random wave-induced onshore scour characteristics; the maximum scour depth, the scour length, and the distance of the maximum scour depth location from the onshore breakwater face. An example of calculation is also provided.  相似文献   

MID-WINTER STEMFLOW DRAINAGE FROM BIGTOOTH ASPEN (POPULUS GRANDIDENTATA MICHX.) IN CENTRAL MASSACHUSETTS     

STANLEY R. HERWITZ  DELPHIS F. LEVIA JR. 《水文研究》1997,11(2):169-175

Under winter conditions, stemflow drainage in forested ecosystems is often assumed to be a negligible component of the hydrological cycle. This paper reports on mid-winter stemflow drainage from the broadleaved deciduous tree species Populus grandidentata. Stemflow volumes from this species at air temperatures of < 0°C were found to be comparable to rainfall-generated stemflow during summer. Over the three-month period January–March 1993, stemflow ranged from 5.4 to 9.9% of the incident gross precipitation. Expressed as depth equivalents per unit trunk basal area, these stemflow inputs ranged from 1.8 to 4.9 m. These concentrated mid-winter inputs of liquid water to the bases of canopy trees were attributable to: (1) snow interception by the leafless woody frame of each tree; (2) snow retention by glazed ice precipitation associated with the snowfall event; (3) increased temperature at the bark/snow interface caused by the low albedo of the bark tissue; and (4) convergence of snowmelt drainage from steeply inclined upthrust primary branches. The hydrological and ecological significance of liquid water inputs to the forest floor under sub-zero conditions are discussed. © 1997 by John Wiley & Sons Ltd.  相似文献   

Burial and scour of short cylinders under combined random waves and currents including effects of second order wave asymmetry     

Dag Myrhaug  Muk Chen Ong 《Coastal Engineering》2009

This paper provides an approach by which the burial and scour of short cylinders under combined second order random waves and currents can be derived. Here the formulas for burial and scour for regular waves plus currents presented by Catano-Lopera and Garcia [Catano-Lopera, Y.A. and Garcia, M.H. (2006). Burial of short cylinders induced by scour under combined waves and currents. ASCE J. Waterway, Port, Coastal and Ocean Eng. 132(6), 439–449., Catano-Lopera, Y.A. and Garcia, M.H. (2007). Geometry of scour hole around, and the influence of the angle of attack on the burial of finite cylinders under combined flows. Ocean Eng. 34(5, 6), 856–869.] are used together with Stokes second order wave theory by assuming the basic harmonic wave motion to be a stationary Gaussian narrow-band random process. An example of calculation is also presented.  相似文献