Palaeogeography, Palaeoclimatology, Palaeoecology, 76 (1989): 153 168
Printed in The Netherlands
Elsevier Science Publishers B.V.. Amsterdam
Denudationrates in the Arctic estimatedfrom lake
Svalbard
sedimentson Spitsbergen,
JOHN INGE SVENDSEN1.JAN MANGERUDl and GIFFORD H. MILLER2
\Uniuersity of Bergen, Department of Geology, Sec. B, Allegt.4l, N'5007 Bergen (Norway)
2Uniuersity of Colorado, INSTAAR, Boulder, CO 80309-0450(U.S.A.)
(Received March 20, 1989; revised and accepted July 19, 1989)
Abstract
Svendsen, J. I., Mangerud, J. and Milier, G. H., 1989. Denudation rates in the Arctic estimated from lake sediments on
Spitsbergen, Svalbard. Palaeogeogr., Palaeoclimatol., Palaeoecol., 76: 153 168.
A mean Holocene denudation rate of 15 mm/1000 yr is calculated for the high arctic valley Linn6dalen, western
Svatbard, based on estimates of the total volume of lacustrine sediments deposited in Lake Linn6vatnet. Thirty-six
sub-bottom sediment profiles and 16 sediment cores have been used to map the postgiacial sediments stored in the lake.
These reveal a lower marine unit overlain by lacustrine sediments. The base and top of the marine sediments were
radiocarbon dated to around 12,300 and 9600 yr B.P. respectively. From isopach maps of the lacustrine unit and the
2
total sediment thickness we calculated 0.9 x 10 km3 of Holocene lacustrine sediments and 20.1 x 10-2 km3 of marine
yr
is calculated from the volume of the lacustrine sediments; this
rate
of
15
mm/1000
sediments. A denudation
demonstrates that fluvial erosion does not contribute significantly to the lowering of the landscape in the present
climate. In contrast, glacial erosion rates in nearby areas on Svalbard are much higher, indicating that glacial erosion
by warm-based valley glaciers is the most important geomorphic process in the present climate. Three km ofTertiary
sediments are postulated to have been removed from central parts ofSvalbard. Our denudation rates suggest that this
could not have occurred in the present interglacial type of climate. We suggest that most of that was removed either in
a warmer climate or by glaciers.
Introduction
Few quantitative studies document denudation rates in high arctic areas. Previous studies
are mainly based on records of fluvial sediment
lransport which do not take into account long
term variations in sediment discharge. In this
study the denudation rate is estimated from
well dated lake sediments which have accumulated throughout the Holocene. As the lake
basin is an efficient sediment trap, the calculated sediment volume provides a basis for a
more precise estimate of the long-term denudation rate. The data from acoustic profiling and
sediment coring of the floor of Lake Linn6vatnet, western Svalbard were used to calculate
sediment volume and total sediment influx into
0031-0182/89/$03.50
the basin. Considering the quality of the data
we collected we consider this to be the most
precise estimate of the denudation rate in high
arctic areas.
This study provides a base for evaluating
which processes were important in the development of the present landscape of Svalbard.
Understanding these processes is important for
evaluating the impact of man on the present
landscape.
Setting
The lake
Lake Linn6vatnet (78'03'N; 13'50'E, Figs.1
and 2) is 4.7km long and 1.3km wide, and is
ac-r1989 Elsevier Science Publishers B.V.
1o4
J. I. SVI]NDSEN ET AL
l sf j o r de n
SVALBARD
L'
,..l
15"
(
B o u n d a r y f o rt h e
catchment area
t
o
o
claciers
_-)
0
Equidisl.50m
n::
ti
*.].'
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.Q;. SVALBARV
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-io"
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,],-*.,
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_-
,lf
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:;Y"-
:' ^o{
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..-,'a i
Fig.1. Map of the study area with key maps of Svalbard and the Norwegian
drainase basin is marked.
nearly 40 m deep in the central part (Fig.3A).
The surface is 12 m a.s.l. and is controlled by a
rock threshold at the northern end of the lake.
At the southern end of the lake, two shallower
(10 15 m deep) sub-basins are separated by a
bathymetric high (Fig.3A). The eastern subbasin receives sediments from the main river, a
meltwater stream from glaciers to the south.
The western sub-basin is largely shielded from
this source by the bathymetric ridge and the
counterclockwise sense of circulation which
transports sediments along the eastern side of
Greenland Sea. The catchment area of the
the lake. The western sub-basin receives most
of its sediment from a secondary meltwater
stream fed by a small cirque, which is currently
almost ice-free, but was glacierized in the
Little Ice Age.
Linn6vatnet is a cold monomictic lake which
is isochemical and isothermal, maintaining a
temperature below 4''C throughout the year
(Boyum and Kjensmo, 1978).The cold climate
generates an ice cover (1.5 -2 m thick) which
persists from late September until July/early
Aueust.
DENUDATION RATES FROM LAKE SEDIMENTS ON SPITSBERGI]N
Fig'2' oblique aerial photo of Lake Linn6vatnet
Research Institute).
and surroundings
Topography
The valley Linn6dalen is bounded by steep
mountain slopes on both sides (Figs.1 and 2).
The highest peak is Griegfjellet (77gm a.s.l.).
The catchment area is 86 km2, 60/" of which is
glacierized (Fig.1). The largest glacier is Linn6_
breen, a 4 km long valley glacier which occu_
pies the head of the valley. Over the past few
decades the glaciers have retreated. This is
evident by comparing the extent ofthe glaciers
at present with the extent indicated on a
topographic map constructed from air photos
taken ih 1936-1988. The maximum extension of
the glaciers during the Holocene is marked by
prominent ice-cored end moraines formed
during the Little Ice Age. Older Neoglacial
moraines, indicate earlier more restricted ad_
vances (Werner, 1988). The older moraines
viewed towards the south (photo:
Norwegian
polar
occur as discontinuous ridges which have
deflectedthe younger advances.
The primary stream, Linn6elva, provid.es
most of the water and sediment to the lake.
This meltwater stream occupiesa single chan_
nel for most of its course and is partly cut into
bedrock. It is therefore assumed that the
present drainage pattern ha'sbeen more or less
similar throughout the Holocene.
Bedrock and superficial sediments
The western part of the drainage area lies
upon the Hecla Hoek Complex, consisting of
metamorphosedquartzites and mica_schistsof
Cambrian and Ordovician age (Flood et al.,
1971)(Fig.a).The rest of the'drainage area lies
on Carboniferous and permian sedimentary
rocks dipping toward the east. The bottom of
156
Fig.3A. Bathymetric map of Lake Linn6vatnet. Coring sites and the sub-bottom profiIes A-B
indicated.
B. Isopach map of the lacustrine sediments.
C. Isopach map of the total sediment thickness.
J. I. SVENDSENET AL.
and B C shown on Fig.b are
DENUDATION RATES FROM LAKE SEDIMENTS ON SPITSBERGEN
LEGEND
M e s o z o i cs h a l e s / s i l t s t o n e s l c h e r t s
G l a ci er s
B o u n d a r y o f l h e c a l c h m e n ta r e a
Linne
breen
c
Fig 4' Simplified bedrock map of the study area (modified from Flood
et al., 1971 and Hjelle et al., 19g6).
the valley is underlain by conglomerates, quartzites and sandstones. Limestone, dolomite and
chert crop out at the eastern side of the valley.
The greater part of the drainage area, except
for the steep valley sides, is covered by a thin and
patchy veneer of superficial sediments including
talus accumulations, till, marine, littoral and
fluvial sediments. However, between Linn6vat_
net and Isfjorden more than 20 m of euaternary
sediments are exposed (Lonne, 1986).Along the
northern and eastern side ofthe lake, Holocene
marine beaches cover most of the land surface
below 60 m a.s.l. (Sandahl, 1986).
Sea leuel history
According to Mangerud et al. (19gT) the
valley was glaciated during the Late Weichselian; deglaciation occurred around 12,300yr
B.P. (Svendsen and Mangerud, 19gg). The
postglacial marine limit is between 6b and Tg m
a.s.l. (Sandahl, 1986; Sandahl et al., 19g7),and
from 12,300 to 9600yr B.P. the valley was a
fjord. During this period there was r:apid uplift,
and by 8000yr B.P. relative sea level had fallen
to 10 m a.s.l. (Sandahl, 1986; Landvik et al.,
1987). The basin was isolated from the sea
forming a lake around 9600 !r B.p. by a beach
terrace at 30 m a.s.l. The outlet river subse_
quently eroded the threshold to the present
level of 12 m a.s.l. The downcutting through
the easily eroded marine gravel and mud was
probably as fast as the uplift, so that the lake
obtained its present shape and level shortlv
before 8000 yr B.P.
Climate and uegetation
The area has an arctic climate, with a mean
annual temperature of - 4.8.C and a mean
158
Methods
piston. The other device is a modification of
Wright's (1967)square rod sampler with a wire
to the piston. The former is more robust and
was used for the deepest corings whereas the
latter is lighter and was preferred for sampling
the lacustrine unit.
The sediment cores were taken in 10 15 m of
water at the southern end of the lake (Fig.3A).
A total of 16 cores up to 12 m in length were
obtained from the lake of which four (no. 1, 5,
14 and 24) penetrated to the bedrock or till. A
preliminary description of the stratigraphy
was provided by Svendsen et al. (1987).
Sub-bottom acoustic profi ling
Dating
The lake floor and its sediment sequencewas
mapped with a 3.5 kHz Raytheon penetrating
echosounding system (RTT-1000,{) during the
summer of 1984 (Mangerud et al., 1985). The
acoustic profiling was carried out by boat; a
total of 36 profiles were recorded with a
combined length of 60 km.
A total of 15 radiocarbon dates are available
from the lake sediments of which 6 are from
directly below the marine/lacustrine boundary
(Table I), and the remainder from the lower part
of the marine unit (Svendsen and Mangerud,
1989). All of the dates were carried out on
marine molluscs. The shell dates are all corrected for a marine reservoir age of 440 years,
which is the correction for Norway; the correction for Svalbard might be slightly higher
(Mangerud and Gulliksen, 1974; Olsson, 1980).
annual precipitation of 400 mm lAkerman,
1980). July is the warmest month with an
average of +4.7"C and March is the coldest
with an average of - I2.2' C. The winter season
is dominated by northeasterly winds, whereas
during the summer southerly and westerly
winds predominate. The area is generally
snow-covered from late September to late May
or early June. The vegetation cover in the
entire valley is patchy, and consists of only
herbs and mosses.
Coring
The lake floor was cored through the ice
during the 1986 spring. Cores were taken with
a piston coring device, yielding individual core
sections up to 2.0 m long with diameters of 110
and 63 mm. The cores were stored in their PVC
core tubes above 0'C. One coring device is a
modified Geonor A/S (Grinidammen 10, Oslo)
samoler with inner rods connected to the
Results
Stratigraphy
The stratigraphy derived from sub-bottom
profiling is consistent throughout the lake
TABI,E I
Radiocarbon dates of molluscs from the top of the marine sediments in the
cores from Lake Linn6vatnet
[,ab. no
Core no.
Core
dePth
(cm,
Depth below
lac./marine
boundary (cm)
rnC Age
(Reservoir corrected
by 440 yr)
T-7365
T-7366
T.7367
AA-3189
AA-3186
GX-13859
14
03
03
09
24
02
616
398
381 396
315
490
236
72
1.7
0 i 5
30
9690+ 130
9660+ 250
9840+ 170
9960+ 110
9860+ 90
+ 190
10,420
26
1<O
DENUDATION RATES FROM LAKE SEDIMENTS ON SPITSBERCEN
silt and clay (Fig.6). The boundary between the
lacustrine and marine formations is very
pronounced and is easily recognized in the
cores. The marine formation is mostly massive,
whereas the lacustrine is strongly laminated in
basin, with two distinct units above the
acoustic basement, a lower massive unit overlain by a subhorizontally layered unit (Fig.5).
The coring showed that the lower unit is
marine, and the upper a laminated lacustrine
Core
no.14
A
A
Westernbasin
Easternbasin
B
0
0
o
E
o
o.s
1.Okm
Fig.5. Two echo-sounding profiIes (3.5 kHz) across the lake. Profile A B is from the southern end of the lake and C D is a
cross section of the main basin (Fig.3A). Note the thick lacustrine sequence in bhe eastern basin compared to the western
basin and also the thickness of the marine sequence in the main basin.
J, I. SVENDSENET AL
a
G R A I NS I Z E
DISTRIBUTION
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Sand tayer
Fig.6. Description of lithostratigraphy
Table I.
from core no. 14. The age of isoration is based on 6 radiocarbon
dates presented in
the lower part directly above the boundary
(Fig.7). The acoustic basement is distinct and is
interpreted as bedrock and/or till. Several
radiocarbon dates of molluscs from the base of
the marine sediment indicate deglaciation
occurred about 12,300yr B.p. or shortlv before
(Svendsen and Mangerud, 19g9). Sheil dates
from the top of the marine unit show that the
lake was isolated from the sea around 9600yr
B.P. (Table I), at which time continuous lacustrine sedimentation began.
Sediment distribution, uolumes,und, influx
rates
Isopach maps for the Holocene lacustrine
sediment (Fig.3B) and the total thickness of
marine and lacustrine sediments were con_
structed from sub-bottom profiling (Fig.3C).
The contour lines were calibrated and adiusted
according to the results from the corirre.
The outline of the present lake is Jerived
from a detailed topographic map at a scale of
161
DENUDATION RATES FROM LAKE SEDIMENTS ON SPITSBERGEN
Core
depth (cm)
Core
depth (cm)
s90
A'
135
rq)
@
@
o
140
o
@
o
60s
145
o
610
150
615
A
B
Fig.?. Photographs of core no. 14.
A. The marine lacustrine boundary.
B. A section of the upper lacustrine
sediments.
1:9300constructed by Akerman (1980).He has,
however, indicated an erroneous scale. We
recalculated the scale by measuring the length
of the lake on the official map Isfjord. We have
used that scale for all area calculations.
In contrast to the marine sediment, a large
share of the lacustrine sediment is found
within the eastern sub-basin, outside the
present delta-front (Fig.3B). The sediment
thickness decreasesdownlake and reflects the
bottom topography. The preferential accumu-
lation of sediment along the eastern margin of
the lake is explained by the summer lake
circulation controlled by the Coriolis force.
The maximum thickness is approximately 12 m
close to the delta front, gradually decreasing
away from the front. The sediment thickness in
the western sub-basin is much less and the
distribution
shows no connection with the
main inflow stream.
The sediments volumes were calculated from
the isopach maps by measuring the area inside
each contour line with a planimeter, and
multiplying this by the contour interval (lm
on the original maps). A straight line approximation has been used for interpolating between each increment of depth. The measured
volume of sediment and the corresponding
average sedimentation rates are presented in
Table II. The average sedimentation rates for
the marine and Incustrine intervals for the
entire lake are 1.6 and 0.2mmlyt respectively.
Unfortunately, due to lack of suitable organic
material we have not yet obtained reliable
sedates from the lacustrine
radiocarbon
quence and have not been able to differentiate
the sedimentation ratqs during the Holocene.
The largest uncertainty in calculating the
the sedisediment volumes is interpretating
ment thickness from the sub-bottom profiles.
However, the coring showed an insignificant
difference between expected and measured
sediment depths and the interpretive error is
considered to be less than 0.3 m for each
contour interval. This means an error of about
TABLE II
Sediment volumes and sedimentation rates calculated from isopach maps
Area
(km')
4.7
Sediment volumesr
(106 m3)
Mean sediment
thickness2
(m)
Lacustrine
Marine
Lacustrine
8.8
20.1
1.9
Marine
Mean sediment
rates3
(mm/yr)
Lacustrine3
Marinea
0.2
lCalculated from isopach maps. These are total volumes, including
2Calculated as sed. volume/area.
3Period of lacustrine sedimentation is 9600 yr.
aPeriod of marine sedimentation is 2700 yr.
the pore water.
162
J, I. SVENDSEN ET AI,,
10/o for the volume of the lacustrine unit. The
uncertainty is larger for the volume of the
marine unit as the acoustic basement on some
of the profiles is indistinct. Another small
source of error is the sediment density and
plotting of the profiling grid. We estimate that
the total error in calculating the sediment
volumes is around L0"/o,and certainlv less than
Volume of lake sediments (106 m3)
25"4.
Porosity (o/o)
Dating uncertainties
The 9600yr B.P. age for the isolation of the
lake is based on averaging 6 dates taking into
account the depth below the marine/lacustrine
sediment boundary and the assumed sedimentation rate (Table I). The age 12,800yr B.p. for
the bottom of the marine unit was determined
from two accelerator radiocarbon dates, carried out on shell in living position (Svendsen
and Mangerud, 1989). From the sub-bottom
profiles we are also fairly sure that the cores
penetrate to the basement. The close agree_
ment between the individual dates indicates
that the dating uncertainty is negligible.
Me(tn denudation rate
Because we have not been able to date the
different levels in the lacustrine sequence, we
have only estimated the mean Holocene (the
last 9600 years) denudation in the catchment
area. Denudation is here defined as the average
ground lowering and is estimated by convert_
ing the volume of lacustrine sediments into a
corresponding volume of bedrock (Table III),
and dividing by the area of the catchment. A
minimum mean denudation rate, 0.0127mm/yr
or 13 mm/1000 yr, is obtained by dividing this
figure by the period of erosion (9600yr). As
discussed below we consider the real denudation rate to be slightly higher (1b mm/1000yr)
due to the loss of sediments at the outlet and
dissolution of rock material in the lake.
The amount of clastic material passing
through the lake was not measured. However,
the form and size of the lake basin indicates
that it is an efficient sediment trap and that the
TABLE III
Physical denudation rate in the catchment area, calculated from the volume of lacustrine sediments stored in
Lake Linn6vatnet
Catchment area
1 p_z:1106 m2)
36.1
8.8
50
Equivalent of bedrock stored as lake sed. (106 m3)
4.4
Sediment dissolved in lake (106 m3)
(maxrmum estimate)
0.s
Sediment lost at outlet (106 m3)
0.2
Volume of eroded bedrock (106 m3)
D-l
Period of erosion (10r yr)
9.6
Physical denudation
rate (mm/103 yr)
amount of sediments which escaped from the
lake is minimal and most certainly less than
5%.
Another source of error is the amount of
rock material dissolved in the lake. The ratio
of calcite to dolomite in the sediment rrans_
ported by fluvial system draining into the Lake
Linn6vatnet is about 1, whereas in the sedi_
ments from the lake the ratio is less than 0.1.
The water chemistry (Boyum and Kjensmo,
1978)shows that the lake is close to saturation
in calcium. We conclude that essentially all
of the calcite particles transported to the lake
is dissolved. This would increase the total
volume of lacustrine sediments by at most 10/o.
The specific gravity of the lake sediments
(1.8 gicm3), which was deteimined from the
weight and volume of the cores, showed little
variation for sediment from the eastern and
western sub-basins, and for the marine and
lacustrine sediments. We have used this value
for the entire lake. However, it should be
mentioned that we have no data from the
central part of the basin where most of the
sediments (57%) are stored. Boyum and
Kjensmo (1980)found that the water content of
the lacustrine sediment from a core taken from
the main basin was around 40l". This indicates
DENUDATION RATES FROM LAKE SEDIMENTS ON SPITSBI]RGEN
that the specific gravity in this part of the lake
is 1.6 g/cm3. Applying that value for the
lacustrine sediments in the central basin
would reduce the total volume of eroded
bedrock bv MD/'. Reducing the specific gravity
of the rock material from the used 2'6 2.5
would increase the denudation rate bv 7"/".
Considering the apparently small amount of
sediments which escaped from the lake, we
conclude that the real physical denudation
rate is only slightly higher than was calculated
from the volume of lacustrine sediments
(13 mm/1000 yr), tentatively 15 mm/1000yr. An
evaluation of all source of errors demonstrates
that the total eruor for the calculated denudation rate is less than +25o/o which is
considered nearly negligible for the main
conclusions.
Discussion
Weathering and erosional processes
The denudation rate calculated here is
exclusively based on estimates of the sediment
volume stored in the lake. Thus, we were not
able to differentiate between weathered or
eroded bedrock, and material eroded from preexisting unconsolidated deposits. Probably the
mean lowering of the bedrock surface was
slightly less than the total volume we obtained.
Littoral erosion
The decrease in the sedimentation rate by a
factor of 7 (Table II) from the marine to the
lacustrine phase is mainly a result of the
reduced contribution of sediments from littoral
processes. The obvious reason for this is
minimal wave action and no tides in the lake,
and that the basin was isolated from longshore
drift. Another factor might be that fewer
unconsolidated sediments were exposed to
wave action during the lake phase.
Glacial erosion
A large share of the current sediment budget
is attributed to glacial erosion, mainly derived
from the sub-polar valley glacier Linn6breen
163
(Figs.1 and 2). Prominent moraines (mostly ice
cored) and outwash fans in front of the glaciers
show that considerable quantities of glacial
sediments are stored in the proglacial zone.
Most of the lacustrine sediment in and beyond
the delta front is siltsize and smaller, suggesting that most of the coarse bed load fraction
produced by the glaciers is deposited upstream.
Repp (1979) demonstrated that the bed load
transport in front of Broggerbreen 100 km
north of this area, amounts to 30/. of the total.
Similar measurements in front of Norwegian
glaciers that are eroding in crystalline rocks
have given values from 30 to 50o/" (Ostrem,
1975). For a small Younger Dryas cirque
glacier in western Norway, Larsen and Mangerud (1981)suggestedthat approximately 80/o
of the glacially eroded material was deposited
in the end moraine and the rest in a small
proglacial lake. They estimated that the bed
load was 47o/" of the sediment transported by
the river. On the basis of field observations and
the referred studies we assume about 50"4 of
the sediment transported by glaciers have been
deposited in the lake.
Elverhoi et al. (1980) calculated an annual
erosion rate of 1 mm for a larger valley glacier
ending in Kongsfjorden, 100 km to the north.
Even though the erosion rates of the smaller
and slower glaciers around Linn6vatnet are
considerably less than this value, we observed
in the field that a large amount of the
sediments transported by the main river originate from the glaciers. This means that the
average denudation rate in the non-glaciated
part ofthe watershed is considerably below the
mean rate of 15 mm/1000 yr.
The sedimentation rate must have varied
depending on the size of the glaciers. Werner
(1988) argues from sedimentological and geochemical criteria that glacial activity was
much greater in the latest half of the Holocene.
To elaborate this, we need precise dates within
the lacustrine unit.
The U-shaped cross section of the valley and
the lake depression (Fig.1) testifies to considerable glacial erosion during the Late Cenozoic.
The survival of a marine terrace and sediments
164
north of the lake which were overriddden by the
ice sheet during the Late Weichselian maximum
(Mangerud et al., 1987) shows that locally
glacial erosion was negligible during the last
glaciation. On the other hand the sub-bottom
profiles suggest that the glacier removed all
older sediments in the lake basin. This may
indicate that glacial erosion mainly took place
beneath the glacier, and that the sides may have
been cold-based much of the time
Fluuial erosion
The presence of an alluvial fan which terminates at the southern shore of the lake as well
as the downcutting of the river Linn6elva into
bedrock bears witness to some fluvial erosion.
However, except for the active gullies, only
minor evidence of fluvial erosion was found. At
present the volume of sediment transported by
fluvial processes is to a large extent of glacial
origin, but the relative importance of the glacial
and subaerial input has not been quantified.
The fluvial erosion rate was probably higher in
the early Holocene following the emergence of
the lake due to reworking of older marine and
lacustrine sediments.
Deflation
Akerman (1980) demonstrated that wind is
an important geomorphological agent only
during the winter season. He measured the
amount of mineral particles in the snow cover
and found that the amount of niveo-eolian
material varied from 0.05 to 0.45 g/l of melted
snow (Akerman, 1980); the median value for
1974 and 1975 was close to 0.1 g/1. This
corresponds to the volume 52 m3 of bedrock
material on the lake surface, or a sedimentation rate of 0.024mm/yr with the given porosity (50/"). This is about I2o/" of the total
sediment influx. This value is probably
underrated as the median value for the Linn6vatnet is higher according to the distribution
map constructed by Akerman (1980).
Physical weathering
Frost-wedging is the most important physical weathering process, and it gives rise to a
variety of debris accumulations below cliffs
within the study area and provides material for
other geomorphological processes of which
gelifluction and surface runoff are the most
important (Akerman, 1980).Rapp (1960),in his
study of slope processes in the inner parts of
Isfjorden, showed that the importance of rock
falls are quantitatively
significant for the
development of the steep mountain wall relief
on Svalbard. He calculated that the postglacial
widening of rock-fall funnels in the walls
corresponds to an average wall retreat of3 5 m
for the Holocene. For the present rate of wall
retreat he obtained values in the range
0.02-0.2 mm/yr. However, he showed that the
amount of material removed from the talus
cones is negligible other than chemical solution. This implies that the greater part of the
rock material contained in talus slopes will
be stored below the cliffs until the debris
eventually is carried away by glacier ice
during the next glaciation. On the basis of field
observations and the referred studies above we
therefore assume that only a small fraction of
frost-rived material is denosited in the lar<e.
Dissolued loud and chemical weathering
The greater part of chemical weathering
occurs on the dolomitic limestone and gypsum
on the eastern side of the valley (Fig.+). This is
also evident from the presence ofseveral karst
features in the area (Salvigsen and Elgersma,
1985).Akerman (1983) estimated the weathering rate on dolomite outcrops in this area to be
2.5 mmi 1000yr. The real denudation is considerably higher due to faster. solution on wet
(buried) surfaces, along fractures, on particles
in the soil, etc. Helld6n (1974)estimated a total
chemical denudation rate of 11.4-15.5mm/
1000yr on dolomites in this area, and Corbel
(1960) obtained 15.75mm on limestones from
other parts of Svalbard. A crude estimate of the
annual dissolved load based on the concentration of ions in the lake water given by Boyum
and Kjensmo (1978), suggests that the mean
chemical weathering in the drainage area is of
the same order of magnitude as the physical
weathering/erosion.
DENUDATION RATES FROM I,AKE SEDIMENTS
ON SPITSBI.]RGEN
165
Comparison with other areas
The denudation rate obtained from
the
sediments in Lake Linn6vatnet has been
compared with the results from cores taken
in a
nearby lake (Skardtjonn) g km south ofLinn6v_
atnet (Landvik et al., 1982) (Fig.1). The lake
drains through a beach ridge 65 m a.s.l. and
we
consider it an efficient sediment trap.
The
sediment thickness indicates that the denuda_
tion in this catchment area is considerably
lower than 20 mm/1000 yr. This supports
the
values calculated from Linn6vatnet.
Few analogous studies exist from the High
Arctic. In a review by Saunders and young
(1983) typical denudation rates of 10-100
mm/
1000 yr for normal relief and 100 1000
mm/
1000yr for steep relief were quoted, whereas
for a polar/montane climate the wide range
of
10-1000mm/1000 yr was given. Based
on
measurements of present fluvial sediment
transport and the total volume of sediments
stored in alluvial fans, Church and Ryder
(I972) estimated denudation rates in
the range
of 150-300 mm/1000 yr on Baffin Island, Arctic
Canada. These estimates of denudation rates
refer to glacial watersheds as in the Linn6dalen valley. The relatively high values
were
attributed to the reworking of existing
sedi_
ment stores by the proglacial rivers.
We
assume that the large difference in denudation
rates between Linn6dalen and Baffin Island
is
primarily due to less glacial cover in
Linn6_
dalen.
Cenozoic landform euolution
Sollid and Sorbel (1988) and Rudberg (1988)
postulated that subaerial processes
such as
weathering and fluvial erosion played
an
important role in the development of
the
present landforms on Svalbard. This
is supported by the widespread occurrence
of weathered material (Kristiansen and Sollid, 19gZ),
alluvial fans and V-shaped valleys. In addition,
the rock-fall funnels and the large amounts
of rock debris which cover the lower slopes
of
the mountains shows that frost action
is
important for the steep mountain wall
relief
(Rapp, 1960).
In spite ofthe existence ofthese features,
the
low denudation rate (1b mm/1000yr) that
we
obtained for Linn6dalen demonstrates
that
subaerial geomorphic processesdo not
contrib_
ute significantly to the lowering of the
landscape in the present climate. The given rate
for
physical denudation would mean
a lowering of
the land surface by only 15 m in one
million
years. If we assume a similar rate for
chemical
denudation (see discussion above), the
total
ground loss would still be less than
B0 m in one
million years. We assume that the
main
reasons for the exceptional low denudation
rate are short-lived thaw seasons and
low
precipitation. A slow subaerial erosion
rate is
also supported by observations made by
Bibus
et al. (1976) in nonglacierized u."u, of
Spit._
bergen. They maintain that accumulation
is
predominant on floors of bigger valleys
which
are not fed by glaciers and consequently
that
no substantial valley formation occurs.
The youngest rocks in central Svalbard
were
deposited during the Eocene, or possibly
Oligo_
cene (Worsley and Aga, 19g6). The removal
of
Tertiary sediments and the development
of the
present alpine landforms is due to post-Eocene
uplift caused by the rifting between Greenland
and Svalbard, which occurred some 86 m.y.
ago
(Eldholm et al., 1984). Based on
two independent methods, namely volume estimates
from a
seismic survey of post-rift sediments to the
west
ofSpitsbergen and velocity depth curves,
Eiken
and Austegard (198g) estimated that 3
km of
Tertiary rocks have been eroded from
the
central part ofSpitsbergen. Vorren et
al. (19gg)
indicated a slightly lower figure (2 2.b km)
from
similar volume estimates of the sedimenrs
stored in the marginal basins in the southern
Barents Sea. This magnitude of erosion was
also
found by Manum and Throndsen (1g7g),
who
used a completely different approach. Based
on
vitrinic reflections of coal bearing Tertiary
strata they showed that an overburden of
about
1.7 km had been removed in central
Spitsber_
gen. From these strata to the bottom
of the
fjords is another kilometer of eroded rocks.
J. I. SVENIJSENET AL.
lbb
Myhre and Eldholm (1988) have provided
evidence from geophysical data, suggesting a
considerable increase in the deposition of
sediments to the west of Svalbard during the
Pliocene/Pleistocene, and that a considerable
part of the total erosion took place the last
5 6 m.y. This interpretation is also supported
by well data from the southern part of the shelf
area (Eidvin et al., 1989;Riis et al., 1989).They
found that the erosion in the Barents Sea
occurred simultaneously with the large glaciations in the area.
A total erosion of 3 km provides a mean
denudation rate of at least 80 m per million
years subsequent to the initiation of seafloor
spreading around 36 m.y. ago. If 2 km was
eroded during PlioceneiPleistocene (maximum
estimate) then the erosion rate is 400 m per
million years. The Holocene denudation rate of
15 m per million years that we obtained for
Linn6dalen is too low to allow for the development of the relief on Svalbard during that
period (0.5 km in 36 m.y.). There are several
possible explanations for this circumstance: (1)
the majority of erosion took place as subaerial
denudation in a warmer and moister climate,
(2) erosion rates were enhanced by periods of
rapid uplift of the archipelago, (3) Pleistocene
glaciations were more effective erosive or
transportive mechanisms. If the young date for
the increase in erosion rate suggested by
Myhre and Eldholm (1988) and Eidvin et al.
(1989)is correct, much of the erosion must have
taken place in an Arctic climate, although part
of the time it could have been wetter and
warmer than the present climate. Nevertheless, the inescapable conclusion from their
dates and our estimate of the present day
denudation rate, is that a considerable part of
the three km of bedrock was removed by
glaciers during the Pliocene and Pleistocene.
A priori we find such a large amount of glacial
erosion difficult to accept, and we will discuss
that in the following paragraPhs.
Evaluating the effectiveness of glacial erosion relative to other terrestrial processes is
complicated by the lack of rigorous data from
similar bedrock terrain. The closest area for
which the rate of glacial erosion has been
determined is in Kongsfjorden (Elverhoi et al.,
1980), 100 km north of Lake Linn6vatnet.
Although the bedrock covered by glaciers
draining into Kongsfjorden to some extent
differ from that of Linn6dalen and may be more
easily eroded, the difference in denudation rate
is almost 70 times greater in Kongsfjorden
Linn6dalen
in
(1000mm/1000yr)
than
(15 mm/1000 yr). Such a large difference suggests that glacial erosion is at least a more
effective transportation agent, and presumably
erosive agent than are other processes currently active on Svalbard. If we use the value
from Elverhoi et al. (1980) as an example, it
would imply an erosion rate of 1000 m in one
million years, making it feasible that glaciers
played an important role in the general lowering of the entire landscape.
The pronounced alpine landscape of Svalbard
indicates that cirque and valley glaciers, rather
than ice-sheets were mainly responsible for
carving the valleys and other high relief land
forms. The Late Pliocene and Early Pleistocene
were probably the most favorable periods for
glacial erosion in areas above sea level. During
these periods the climatic variations were
smaller in amplitude and presumably the temperatures were higher during the ice ages and
lower during the interglacials, as compared to
the Late Pleistocene period (Jansen et al., 1987).
This would favor the development of erosive
(warm-based) valley and cirque glaciers on
Svalbard. On the other hand, erosion of the
major fjords below sea level requires large ice
sheets, with outlet glaciers at the pressure
melting point at their base and thus able to
erode. Sedimentological records in deep sea
cores indicate that the first major expansion of
ice sheets in the Northern Hemisphere occurred
at about 2.4-2.5 Ma (Shackleton et al., 1984;
Jansen et al., 1987).The greater part ofthe fiord
bathymetry must have been eroded after that.
Conclusions
In this high arctic area the subaerial physical denudation rate is verv low. Even if the
167
DENUDATION RATES FROM LAKE SI]DIMENTS ON SPITSBERGEN
calculated value (15 mm/1000 yr) for Linn6dalen was doubled it would not significantly
affect this conclusion.
Other studies have demonstrated that some
3 km ofTertiary bedrock has been removed from
Central Svalbard. The denudation rate we
obtained for the present environment would
allow removal of only 0.5 km during the given
period. We consider that most of the missing bedrock was removed either in a warmer Pliocene/
Pleistocene climate or by glacial erosion.
The rate of chemical weathering on carbonate and gypsum bedrock is of the same order of
magnitude as the physical subaerial denudation rate. Locally it may exceed the rate of
glacial erosion, but readily soluble rocks are
missing in the central Tertiary basin.
A direct short-term consequence of the given
low denudation rate is that this type of
landscape is more susceptible to all kinds of
ground surface disturbances because it will
"infinite"
time to restore itself' One
take
conclusion which should be drawn from this is
that Man should be aware of the consequences
of disturbing this kind of landscape.
Acknowledgements
This paper resulted from a co-operative
project between the University of Bergen and
the University of Colorado led by Jan Mangerud and Gifford H. Miller. The project was
funded by grants from the Norwegian Research
Council for Science and Humanities (NAVF),
the U.S. National Science Foundation (DPP8413128), Statoil and the Norwegian Polar
Research Institute, which also provided logistic support. The Norwegian Geological Survey
(NGU) provided financial support to the development of the coring advice. Jon Landvik was
responsible for the logistical implementation
of the coring and also participated in the
fieldwork. Arne Rasmussen constructed the
isopach maps. The crew on the Isfjord Radio
Station, together with their chief Arnold
Torum, were most helpful during the fieldwork.
To all of these colleagues and institutions we
offer our sincere thanks.
References
Akermann, J.. 1980. Studies on periglacial geomorphology
in west Spitsbergen. Medd. Lunds Univ. Geogr. Inst. Ser.
Avh., 89, 297 pp.
Akermann, J., 1983. Notes on chemical weathering, Kapp
Linn6, Spitsbergen. In: Proc. 4th Int. Permafrost Conf.,
Washington, 1983, pp. 10 15.
Bibus, E., Nagel, G. and Semmel, A., 1976.Periglaziale relief
formong in zentralen Spitsbergen. Catena, 3:29 44Boyum, A. and Kjensmo, J., 19?8. Physiography of Lake
Linn6vaten, western Spitsbergen. Verh. Int. Ver. Limnol., 20:609 614.
Boyum, A. and Kjensmo, J., 1980. Postglacial sediments in
Lake Linn6vatnet, Western Spitsbergen. Arch. Hydrobiol.,88: 232 249.
Corbel. J.. 1960. Nouvelles recherches sur les karst
arctiques Scandinavies. Z. Geomorphol. Suppl.' 2:74 80.
Church, M. A. and Ryder, J., lgT2.Pataglacial sedimentation: a consideration of fluvial processes. Geol. Surv.
Can. Bull.. 83: 3059 3072.
Eidvin, T., Fjeldskaar, W. and Riis, F., 1989. Ny datering av
Tertier erosjon i Barentshavet. In: Nor. Geol. Foren. 11
Landsmote. Sammendrag av etteranmeldte foredrag,
Bergen, 1989.
Eiken, O. and Austegard, A., 1988. The Tertiary belt of
West-Spitsbergen: Seismic expressions of the offshore
sedimentary basins. Nor. GeoI. Tidsskr.,67: 383 394'
Eldhotm, O., Sundvor, E., Myhre, A. and Faleide' J. I.' 1984.
Cenozoic evolution of the continental margin off Norway and western Svalbard. In: A. M. Spencer (Editor)'
Petroleum Geoiogy of the North European Margin.
Graham and Trotman, London, PP' 3 18.
Elverhoi, A., Liestsl, O. and Nagy, J., 1980. Glacial
erosion, sedimentation and microfauna in the inner part
of Kongsfjorden, Spitzbergen. Nor. Polarinst. Skr., 172:
33 62.
Flood, B., Nagy, J. and Winsnes, T. S., 1971. Geological
map. Svalbard 1: 500,000.Sheet IG Spitsbergen, southern
part. Nor. Polarinst. Skr., 154 A.
Heltd6n, IJ., 1974. Karst. En studie i Artfjdllets karstomrAde samt jamforande korrosjonsanalyser frAn Vdstspetsbergen och Tjeckoslovakien' Medd. Lunds Univ.
Geogr. Inst. Ser. Avh., 72, l92PP.
Hjelle, A., Lauritzen, O., Salvigsen, O. and Winsnes' T. S.,
1986. Geological map. Svalbard 1:100.000. Sheet B10G
Van Mijenfjorden. Nor. Polarins't. Temakart No. 2.
Jansen, E., Bleil, U., Henrich, R., Kringstad' R. and
Slettemark, 8., 198?. Climatic changes in the Norwegian
Sea during the last 2.8 Ma. Polar Res., 5 n.s.: 329 332.
Kristiansen, K. J. and Sollid, J. L., 1987. Svalbard,
jordartskart 1:1000.000.Nasjonalatlas for Norge. Geogr.
Inst. Univ. Oslo.
Landvik, J. Y., Mangerud, J. and Salvigsen, O., 1987. The
late Weichselian and Holocene shoreline displacement
on the west coast of Svalbard. Polar Res.' 5 n.s.: 1 10.
Larsen, E. and Mangerud, J., 1981. Erosion rate of a
Younger Dryas cirque glacier at Krikenes' Western
Norway. Ann. Glaciol., 2: 153 158.
Lsnne. I., 1986. Weichsel stratigrafi,
sedimentologi
og
ETAL.
J. I, SVENDSEN
168
glasitektonikk i snittene langs Linneelva, Ytre Isfjorden, Svalbard. Thesis. Univ. Bergen.
Mangerud, J., Landvik, J. Y., Saivigsen, O. and Miller, G.
H., 1985. Lake Linn6vatnet, Svalbard, a possible 40,000
years continuous record of lacustrine and marine
sedimentation. In: Abstr. 14th Arctic Workshop, Arctic
Land Sea Interactions, Bedford Inst. Oceanogr., Darthm o n t h , 1 9 8 5 ,p p . 8 2 8 5 .
Mangerud, J., Bolstad, M., Elgersma, A., Helliksen, D.,
Landvik, J. Y., Lycke, A.K., Lonne, I., Salvigsen, O.,
S a n d a h l , T . a n d S e j r u p , H . P . , 1 9 8 7 .T h e L a t e W e i c h s e l ian glacial maximum in western Svalbard. Polar Res., 5
n.s.:275 278.
Mangerud, J. and Gulliksen, S., 1974. Apparent radiocarbon age of Recent marine shelis from Norway, Spitsbergen and Arctic Canada. Quat. Res., 5:263 273.
M a n u m , S . B . a n d T h r o n d s e n , T . , 1 9 7 8 .R a n k o f c o a l a n d
dispersed organic matter in its geoiogical bearing in the
Nor. Polarinst. Arbok, 1977:
Spitsbergen Tertiary.
toY 1/I.
Myhre, A. M. and Eldholm, O., 1988.The Western Svalbard
margin (74" 80"N). Mar. Pet. Geol., 5: 134 156.
raC in marine mammals from
Olsson. I. U., 1980. Content of
northern Europe. Radiocarbon, 22:662 675.
Rapp, A., 1960. Talus slopes and mountain walls at
Tempelfjorden, Spitsbergen. Nor. Polarinst. Skr., 119,
69 pp.
Repp, K., 1979. Breerosjon, glasio-hydrologi og material
transport i et hoyarktisk miljo Broggerbreene, Vestspitsbergen. Thesis. Univ. Osio, 136 pp. (Unpublished).
Riis, F., Eidvin, E. and Fjeldskaar, W., 1989. Cenozoic
tectonics and Pliocene deposition, western Barents Sea.
Fifth meeting of the European Union of Geoscrences,
Strasbourg 20 23 March 1989. Terra Abstr., 1: 25.
Rudberg, S., 1988. High arctic landscapes, comparisons and
reflections. Nor. Geogr. Tidsskr., 42:255 264.
Salvigsen, O. and Elgersma, A., 1985. Large scale karst
features and open talliks at Vardeborgsietta, outer
Isfjorden, Svalbard. Polar Res., 3 n.s.: 145 153.
undersokelser i
Sandahl, T., 1986. Kvartargeologiske
omrAdet Lewinodden Kapp Starostin Linn6vatnet Ytre
Isfjorden, Svalbard. Thesis. Univ. Bergen (unpublished).
Sandahl, T., Mangerud, J. and Salvigsen, O., 1987. The
lateglacial marine limit and a sea-level curve from
Linn6dalen. westcoast of Svalbard. In: Abstr. Late
Cenozoic Palaeoenvironment and Geology of the Arctic,
Symp. Spidsbergseter Fjellstue, Norway, Aprii 1987.
Nor. Polar Res. Inst., pp. 16.
Saunders, I. and Young, A., 1983. Rates of surface
processes on slopes, slope retreat and denudation. Earth
S u r f . P r o c e s s e sL a n d f o r m s , 8 : 4 7 3 5 0 1 .
Shackleton, N. J., Backman, J., Zimmerman, H., Kent, D.
V., Hall, M. A., Roberts, D. G., Schnitker,. D., Baldauf, J.
G., Desprairies, A., Homrighausen, R., Huddlestun, P.,
Keene, J. 8., Kaitenback, A. J., Krumsiek, K. A. O.,
Morton, A. C., Murray, J. W. and Westberg-Smith, J.,
1984. Oxygen isotope calibration of the onset of icerafting and history of glaciation of the North Atlantic
region. Nature, 307: 620 623.
So]]id, J. L. and Sorbel, L., 1988. Utbredelsesmonsteret av
lssmateriale og landformer pA Svaibard Noen hovedtrekk. Nor. Geogr. Tidsskr.,42:265 27O.
Svendsen,J. I., Landvik, J. Y., Mangerud, J. and Miller,
G. H., 1987. Postglacial marine and lacustrine sediments
in Lake Linn6vatnet, Svalbard. Polar Res., 5 n.s.:
287 283.
Svendsen, J. I. and Mangerud, J., 1989. Late Weichselian
glacial history, inferred from the marine sediments in
Lake Linn6vatnet, Svalbard (unpublished).
V o r r e n , T . O . , L e b e s b y e ,E . , H e n r i k s e n , E . , K n u t s e n , S . M .
and Richardsen, G., 1988. Cenozoic erosjon og sedimentasjon i det sorlige Barentshav. In: Abstr. 18 Nordiske
Geologiske Vintermode, Kobenhavn, 1988. Dan. Geol.
Unders., pp.424.
Werner, A., 1988.Holocene glaciation and climatic change,
Spitsbergen, Svalbard. Thesis. Dep. Geol. Sci. Univ.
Colorado, 296 pp. (unpublished).
Worsley, D. and Aga, O.J. (Editors), The Geological History
of Svalbard. Den norske stats oljeselskap, Stavanger,
121pp.
Wright, H. E., Jr., 1967. A square-rod piston sampler for
lake sediments.J. Sediment. Petrol., 37:975 976.
Ostrem, G., 1975. Sediment transport in glacial meltwater
streams. In: A. V. Jopling and B. C. MacDonald
(Editors). Glaciofluvial and Glaciolacustrine Sedimentation. Soc. Econ. Paleontol. Mineral. Spec. Publ., 23;
707 722.