Suspended sediment transport and deposition of cyclically interlaminated sediment in a temperate glacial fjord, Alaska, U.S.A.

Abstract Cyclically interlaminated sediment is a distinctive lithofacies within the sediment package of temperate glacial fjords. The tidewater terminus of McBride Glacier is at the head of a small fjord that receives abundant suspended sediment and is a site of rapid accumulation of cyclically interlaminated sediment. Buoyant sediment-laden meltwater rises from a subglacial stream at the base of the glacier and mixes with fjord water to produce a thick, brackish overflow. Peak suspended sediment concentrations occur beneath the surface of the overflow at 3 to 10 m depth. Particle release from the overflow is controlled by semi-diurnal tidal fluctuations. The major vertical flux of suspended sediment is initiated at low tide because of low horizontal current velocities and reduced vertical eddy velocities. Sorting occurs as the particles settle; sand and coarse silt settle as single grains and finer flocculated particles settle as turbid layers at a rate between 2.5 m/h and 10.9 m/h. Each low water produces a couplet of a coarser grained lamina that is sorted as coarser single grains settle, and a finer grained lamina of flocculated particles in turbid layers. Individual couplet thicknesses and particle size decrease with distance from the discharge source. Semi-diurnal tides produce two couplets each day. Interstratified with these tidal rhythmites are coarser and poorly sorted laminae deposited by sediment gravity flows and coarse laminae contributed by peak daily discharge.

[1]  B. Molnia.  Subarctic Glacial-Marine Sedimentation: A Model , 1983 .

[2]  C. M. Hoskin,et al.  Suspended sediment dynamics in Blue Fjord, western Prince William Sound, Alaska☆ , 1978 .

[3]  K. Kranck.  Settling Behavior of Cohesive Sediment , 1986 .

[4]  C. M. Hoskin,et al.  Sediment Transport and Accumulation in a Fjord Basin, Glacier Bay, Alaska , 1972, The Journal of Geology.

[5]  Cheryl Ann Butman,et al.  Sediment trap biases in turbulent flows: Results from a laboratory flume study , 1986 .

[6]  B. Hargrave,et al.  Assessment of sediment trap collection efficiency , 1979 .

[7]  A. Post,et al.  Columbia Glacier, Alaska; recent ice loss and its relationship to seasonal terminal embayments, thinning, and glacier flow , 1979 .

[8]  S. Blomqvist.  Sediment trapping-A subaquatic in situ experiment1 , 1981 .

[9]  E. Domack.  Rhythmically bedded glaciomarine sediments on Whidbey Island, Washington , 1984 .

[10]  R. Gilbert.  Sedimentary processes of Canadian arctic fjords , 1983 .

[11]  J. Syvitski,et al.  Fjords: Processes and Products , 1986 .

[12]  K. Stolzenbach,et al.  Predictions of sediment trap biases in turbulent flows: A theoretical analysis based on observations from the literature , 1986 .

[13]  G. Kocurek.  The Petrology of the Sedimentary Rocks , 1938, Nature.

[14]  C. Officer.  Physical dynamics of estuarine suspended sediments , 1981 .

[15]  R. Powell,et al.  Glacimarine sedimentary processes, facies and morphology of the south-southeast Alaska shelf and fjords , 1989 .

[16]  J. Syvitski,et al.  The prodelta environment of a fjord: suspended particle dynamics , 1985 .

[17]  R. Powell.  A Model for Sedimentation by Tidewater Glaciers , 1981, Annals of Glaciology.

[18]  R. Powell,et al.  Glacimarine processes at grounding-line fans and their growth to ice-contact deltas , 1990, Geological Society, London, Special Publications.

[19]  N. Eyles,et al.  Glacial facies models , 1988 .

[20]  N. Eyles,et al.  Models of glaciomarine sedimentation and their application to the interpretation of ancient glacial sequences , 1985 .

[21]  P. Carlson,et al.  Interlaminated ice-proximal glacimarine sediments in Muir Inlet, Alaska , 1984 .

[22]  A. Elverhøi,et al.  Glaciomarine sedimentation in a modern fjord environment, Spitsbergen , 1983 .

[23]  K. Görlich.  Glacimarine sedimentation of muds in Hornsund Fjord, Spitsbergen , 1986 .

[24]  J. Syvitski.  On the deposition of sediment within glacier-influenced fjords: Oceanographic controls , 1989 .

[25]  R. Powell.  Glacial-Marine Sedimentation Processes and Lithofacies of Temperate Tidewater Glaciers, Glacier Bay, Alaska , 1983 .

[26]  D. Reed.  Tidal Currents and Glacial Discharge, Laguna San Rafael, Southern Chile , 1988 .

[27]  N. Smith,et al.  Rainstorm-induced event sedimentation at the tidewater front of a temperate glacier , 1988 .