Kc. Seramur et al., EVALUATION OF CONDITIONS ALONG THE GROUNDING LINE OF TEMPERATE MARINEGLACIERS - AN EXAMPLE FROM MUIR INLET, GLACIER BAY, ALASKA, Marine geology, 140(3-4), 1997, pp. 307-327
In the marine environment, stability of the glacier terminus and the l
ocation of subglacial streams are the dominant controls on the distrib
ution of grounding-line deposits within morainal banks. A morainal ban
k complex in Muir Inlet, Glacier Bay, SE Alaska, is used to develop a
model of terminus stability and location of subglacial streams along t
he grounding line of temperate marine glaciers. This model can be used
to interpret former grounding-line conditions in other glacimarine se
ttings from the facies architecture within morainal bank deposits. The
Muir Inlet morainal bank complex was deposited between 1860 A.D. and
1899 A.D., and historical observations provide a record of terminus po
sitional glacial retreat rates and sedimentary sources. These data are
used to reconstruct the depositional environment and to develop a cor
relation between sedimentary facies and conditions along the grounding
line. Four seismic facies identified on the high-resolution seismic-r
eflection profiles are used to interpret sedimentary facies within the
morainal bank complex. Terminus stability is interpreted from the dis
tribution of sedimentary facies within three distinct submarine geomor
phic features, a grounding-line fan, stratified ridges, and a field of
push ridges. The grounding-line fan was deposited along a stable term
inus and is represented on seismic-reflection profiles by two distinct
seismic facies, a proximal and a distal fan facies. The proximal fan
facies was deposited at the efflux of subglacial streams and indicates
the location of former glacifluvial discharges into the sea. Stratifi
ed ridges formed as a result of the influence of a quasi-stable termin
us on the distribution of sedimentary facies along the grounding line.
A field of push ridges formed along the grounding line of an unstable
terminus that completely reworked the grounding-line deposits through
glacitectonic deformation. Between 1860 A.D. and 1899 A.D. (39 years)
, 8.96 x 10(8) m(3) of sediment were deposited within the Muir Inlet m
orainal bank complex at an average annual sediment accumulation rate o
f 2.3 x 10(7) m(3)/a. This rate represents the annual sediment product
ion capacity of the glacier when the Muir Inlet drainage basin is fill
ed with glacial ice. (C) 1997 Elsevier Science B.V.