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Properties of suspended sediment over the HEBBLE area on the Nova Scotian Rise
OLR (1986)33 (3)
D. Submarine Geology and Geophysics
of clay mineral diagenesis and itself varies systematically with burial depth and temperature. Dept. of Geol., Beaumont Bldg., Univ. of Sheffield, Brookhill, Sheffield $3 7HF, UK. 86:1556 DeMaster, D.J., B.A. McKee, C.A. Nittrouer, D.C. Brewster and P.E. Biscaye, 1985. Rates of sediment reworking at the HEBBLE site [Nova Scotian continental rise] based on measurements of Th-234, Cs--137 and Pb-210. Mar. Geol., 66(1-4): 133-148.
Th-234 data from HEBBLE cores indicate that particles at the sediment-water interface are mixed to depths of 1-5 cm on a 100-day time scale. Cs-137 and Pb-210 data indicate that on time scales of 30-100 yrs surface sediments are reworked to depths ranging 1 to 12 cm. In some HEBBLE sediments there is good agreement between the Th-234 and the Pb-210 mixing coefficients; in others, however, Th-234 data indicate that the Pb-210 profile has not reached steady state. Implications for modelling are noted. Dept. of Mar., Earth and Atmos. Sci., North Carolina State Univ., Raleigh, NC 27695-8208, USA. 86:1557 Hagan, P.S. and D.S. Cohen, 1985. Stratified layer formation in particle suspensions. Physica, The Hague, 17D(1):54-62.
Initially homogeneous suspensions of colloidal particles often develop 'staircase' layers of nearly constant concentration, separated by sharp boundaries, with the concentration of each successive layer increasing with depth. Siano has demonstrated experimentally that diffusion against the concentration gradient occurs. Thus, these patterns appear to be the result of spinodal decomposition. These patterns cannot be explained by the classical spinodal decomposition theory of Cahn and Hilliard, but they can be explained if the linear gradientenergy term of Tiller, Pound, and Hirth is added to the free energy. The physical origin of this extra term may be the Rayleigh-Taylor instability. Exxon Corp. Sci. Lab., Rte. 22 East, Aunandale, NJ 08801, USA. 86:1558 Hanes, D.M. and A.J. Bowen, 1985. A grunuiar-fluid model for steady intense bed-load transport. J. geophys. Res., 90(C5):9149-9158.
Flow is modeled as two fluid regions with continuous stress, velocity, and granular concentration; a simple kinematic model is developed to predict the grain transport in the saltation zone and to provide the upper boundary conditions for the granular-fluid region. Velocity in the latter is approximately
225
proportional to the applied shear stress raised to the 3/2 power under the assumption of a linearly varying volume concentration. The grain flux and energy dissipation are proportional to the applied shear stress raised to the 5/2 power. Compared with observations and previous models, the present formulation predicts significantly greater transport at extremely high stresses. RSMAS, Univ. of Miami, FL 33149, USA. 86:1559 McCave, I.N., 1985. Properties of suspended sedi. ment over the HEBBLE area on the Nova S¢otlan Rise. Mar. Geol., 66(1-4):169-188.
Twenty samples from 20, 40, 250 and 1000 m above bottom were analysed by Coulter Counter giving a size range of 1.59-256/an. Aggregates were common in most samples, particularly with associated mucus. Blobs and strings of mucus were common with and without particles. Apparent density of particles (a) increases with overall concentration, but Co) decreases with increasing concentration when only larger particles are included. This probably reflects (a) aggregation during ageing of a suspension and (b) presence of more mucus in larger coarse-mode populations. Dept. of Earth Sci., Univ. of Cambridge, Downing St., Cambridge CB2 3EQ, UK. 86:1560 McCave, I.N. and C.D. Hollister, 1985. Sedimentatiun under deep-sea current systems: preHEBBLE ideas. Mar. Geol., 66(1-4):13-24.
Studies of the interaction of deep ocean current systems with the seabed are briefly traced from their beginnings in the mid-1950s. Subsequent lines of study in physical oceanography, suspended sediment measurement, echo-character mapping, microphysiography, sedimentology and developments of instrumentation are noted up to 1978 when the High Energy Benthic Boundary Layer Experiment started. Dept. of Earth Sci., Univ. of Cambridge, Downing St., Cambridge CB2 3EQ, UK. 86:1561 McLean, S.R., 1985. Theoretical m o ~ l l i n ~ of deep ocean sediment tr~sport. Mar. Geol., 6604):243-265. The physics of the general processes involved in the resuspension, transport, and deposition of sediments is examined using a 'quasi-one-dimensional' modelling approach which is then applied to threedimensional site specific models. The interrelationships of boundary shear stress, the Ekman layer, sediment entrainment, stratification, turbulence, cohesion, material size, etc. are explored and
D. Submarine Geology and Geophysics
of clay mineral diagenesis and itself varies systematically with burial depth and temperature. Dept. of Geol., Beaumont Bldg., Univ. of Sheffield, Brookhill, Sheffield $3 7HF, UK. 86:1556 DeMaster, D.J., B.A. McKee, C.A. Nittrouer, D.C. Brewster and P.E. Biscaye, 1985. Rates of sediment reworking at the HEBBLE site [Nova Scotian continental rise] based on measurements of Th-234, Cs--137 and Pb-210. Mar. Geol., 66(1-4): 133-148.
Th-234 data from HEBBLE cores indicate that particles at the sediment-water interface are mixed to depths of 1-5 cm on a 100-day time scale. Cs-137 and Pb-210 data indicate that on time scales of 30-100 yrs surface sediments are reworked to depths ranging 1 to 12 cm. In some HEBBLE sediments there is good agreement between the Th-234 and the Pb-210 mixing coefficients; in others, however, Th-234 data indicate that the Pb-210 profile has not reached steady state. Implications for modelling are noted. Dept. of Mar., Earth and Atmos. Sci., North Carolina State Univ., Raleigh, NC 27695-8208, USA. 86:1557 Hagan, P.S. and D.S. Cohen, 1985. Stratified layer formation in particle suspensions. Physica, The Hague, 17D(1):54-62.
Initially homogeneous suspensions of colloidal particles often develop 'staircase' layers of nearly constant concentration, separated by sharp boundaries, with the concentration of each successive layer increasing with depth. Siano has demonstrated experimentally that diffusion against the concentration gradient occurs. Thus, these patterns appear to be the result of spinodal decomposition. These patterns cannot be explained by the classical spinodal decomposition theory of Cahn and Hilliard, but they can be explained if the linear gradientenergy term of Tiller, Pound, and Hirth is added to the free energy. The physical origin of this extra term may be the Rayleigh-Taylor instability. Exxon Corp. Sci. Lab., Rte. 22 East, Aunandale, NJ 08801, USA. 86:1558 Hanes, D.M. and A.J. Bowen, 1985. A grunuiar-fluid model for steady intense bed-load transport. J. geophys. Res., 90(C5):9149-9158.
Flow is modeled as two fluid regions with continuous stress, velocity, and granular concentration; a simple kinematic model is developed to predict the grain transport in the saltation zone and to provide the upper boundary conditions for the granular-fluid region. Velocity in the latter is approximately
225
proportional to the applied shear stress raised to the 3/2 power under the assumption of a linearly varying volume concentration. The grain flux and energy dissipation are proportional to the applied shear stress raised to the 5/2 power. Compared with observations and previous models, the present formulation predicts significantly greater transport at extremely high stresses. RSMAS, Univ. of Miami, FL 33149, USA. 86:1559 McCave, I.N., 1985. Properties of suspended sedi. ment over the HEBBLE area on the Nova S¢otlan Rise. Mar. Geol., 66(1-4):169-188.
Twenty samples from 20, 40, 250 and 1000 m above bottom were analysed by Coulter Counter giving a size range of 1.59-256/an. Aggregates were common in most samples, particularly with associated mucus. Blobs and strings of mucus were common with and without particles. Apparent density of particles (a) increases with overall concentration, but Co) decreases with increasing concentration when only larger particles are included. This probably reflects (a) aggregation during ageing of a suspension and (b) presence of more mucus in larger coarse-mode populations. Dept. of Earth Sci., Univ. of Cambridge, Downing St., Cambridge CB2 3EQ, UK. 86:1560 McCave, I.N. and C.D. Hollister, 1985. Sedimentatiun under deep-sea current systems: preHEBBLE ideas. Mar. Geol., 66(1-4):13-24.
Studies of the interaction of deep ocean current systems with the seabed are briefly traced from their beginnings in the mid-1950s. Subsequent lines of study in physical oceanography, suspended sediment measurement, echo-character mapping, microphysiography, sedimentology and developments of instrumentation are noted up to 1978 when the High Energy Benthic Boundary Layer Experiment started. Dept. of Earth Sci., Univ. of Cambridge, Downing St., Cambridge CB2 3EQ, UK. 86:1561 McLean, S.R., 1985. Theoretical m o ~ l l i n ~ of deep ocean sediment tr~sport. Mar. Geol., 6604):243-265. The physics of the general processes involved in the resuspension, transport, and deposition of sediments is examined using a 'quasi-one-dimensional' modelling approach which is then applied to threedimensional site specific models. The interrelationships of boundary shear stress, the Ekman layer, sediment entrainment, stratification, turbulence, cohesion, material size, etc. are explored and