Geomorphic Evidence for Late Glacial Ice Dynamics on Southern Baffin Island and in Outer
Hudson Strait, Nunavut, Canada
Author(s): Johan Kleman, David Marchant, Ingmar Borgstrom
Source: Arctic, Antarctic, and Alpine Research, Vol. 33, No. 3 (Aug., 2001), pp. 249-257
Published by: INSTAAR, University of Colorado
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Arctic, Antarctic, and Alpine Research, Vol. 33, No. 3, 2001, pp. 249-257
Evidence
forLateGlacial
IceDynamics
onSouthern
Baffin
Island
Geomorphic
andinOuter
Hudson
Canada
Strait,Nunavut,
Johan Kleman,* David
Marchant, and Ingmar
Borgstrom*
*Departmentof Physical Geography,
StockholmUniversity,S-106 91,
Stockholm,Sweden.
kleman@natgeo.su.se
tDepartmentof EarthSciences,
Boston University,685
CommonwealthAvenue, Boston,
Massachusetts02215, U.S.A.
Abstract
We here describe glacial geomorphology that sheds light on ice-dynamic conditions during the Noble Inlet advance, a glacial event involving northward ice flow
across Hudson Strait and large-magnitude meltwater drainage across Meta Incognita Peninsula at around 8.9 to 8.4 14C kyr BP Through airphoto interpretation
and field inspection of key sites we mapped the glacial geomorphology of interior
Meta Incognita Peninsula, the postulated terminal zone for northward expansion
of ice from Quebec-Labrador during the Noble Inlet advance. A 170-km-long
zone of glaciofluvial canyons, washing zones and boulder deltas was traced from
Shaftesbury Inlet to Henderson Inlet. This zone reflects initial drainage across
Meta Incognita Peninsula at >520 m elevation, followed by ice marginal drainage
at progressively lower levels along the southern slope of the peninsula. The ice
marginal outline required to explain the glaciofluvial zone is compatible with
northward-trending striae previously reported from the southern coast of Meta
Incognita Peninsula. A very large flux of meltwater across Meta Incognita Peninsula probably occurred because eastward supraglacial drainage on ice in Hudson
Strait was temporarily impeded and steered northward by a raised ice surface
level in outer Hudson Strait, induced by an enhanced outflow of ice from Ungava
Bay.
Introduction
The Hudson Strait area is crucial to understandingLaurentide ice sheet dynamics, because topography suggests it was a
major route for ice streams draining interior Laurentideice directly into the ocean. A major ice stream, with a catchment up
to a third of the LaurentideIce Sheet area, is postulated to have
existed in Hudson Strait throughthe deglacial stages of the Late
Wisconsinan (Fischer et al., 1985). This glaciological concept
was complicated by the discovery of a regional patternof northward-trendingstriationsand calcareous till on the southerncoast
of Meta Incognita Peninsula, suggesting a perplexing cross-strait
ice flow instead of along-strait flow (Miller et al., 1988). This
expansion followed an earlier event of northwardexpansion of
ice in the outer Hudson Strait region, the Gold Cove advance
(Stravers et al., 1992), which reached the Hall Peninsula. The
reality of cross-strait flow was called into question by England
and Smith (1993), but defended by Kaufman et al. (1993).
The possibility of Labradorice impinging on the peninsula
was first suggested by Mercer (1956), who pointed at such an
ice configurationas the only possibility to explain the very large
meltwater gorges (York canyons) which cut across the backbone
of the Meta Incognita Peninsula. On the basis of radiocarbondated ice-marginal deltas on the tip of Meta Incognita Peninsula,
dating of marine and glaciomarine sediments in Hudson Strait
cores, and the radiocarbonages of molluscs reworked into till,
Miller et al. (1988), Stravers et al. (1992), and Manley (1995)
suggested that the cross-strait flow, dated at 8.9 to 8.4 kyr (14C)
BP was a readvance (Noble Inlet readvance) of ice from the
Labrador dome across a previously deglaciated Hudson Strait
(Andrews et al., 1995). The timing of glacifluvial drainage
through the York canyons is constrainedto 9.0 to 8.6 kyr BP by
radiocarbondated shells in the York delta (Blake, 1966; Muller
1980; Manley, 1995), immediately outside the canyon mouths.
We here focus on the glacial landforms of interior Meta
Incognita Peninsula, the postulated terminal zone for this advance. We report new mapping of the glacial geomorphology of
the peninsula, especially the patternof ice marginalglaciofluvial
drainage.The specific problem we address is the possible source
of water for the drainage across the Meta Incognita Peninsula
(Laymon, 1988), and the glaciological conditions during this
event.
Methods
The glacial geomorphology of southern Baffin Island was
mapped throughinterpretationof airphotosat a scale of 1:60,000
(Kleman and Jansson, 1996). Figure 1 shows key elements of
the glacial geomorphology of outer Meta Incognita Peninsula.
We scrutinized the inland part of the peninsula for marginal deposits and striae that could possibly be related to a northward
advance of ice from a southerly source area (the Noble Inlet
advance). Fieldwork was focused where we expected a wet-bed
advance would have created northwardstriations 30 km inland
from the coast. We examined several coarse-grainedglaciofluvial
deposits in the main drainage zone, searching for evidence of
postdepositional disturbance. Helicopter reconnaissance was
flown along the main drainage zone, the York canyons, and the
York delta. The highest (105 m) and oldest terrace of the York
delta was searched for dateable material.
andOverall
Physiography
Geomiorphology
Outer Meta Incognita Peninsula (east of Lake Harbour)is
a fault-bounded tectonic block of granites and gneisses. It is
J. KLEMAN ET AL. / 249
FIGURE 1. (a) Location map. (b) Glacial and glaciofluvial landforms of Meta Incognita Peninsula. Thin
lines represent fluting and grooving, and thin arrows show such landforms with orientation determined.
Thick arrows represent glaciofluvial canyons, washing zones, and channels. Dark shading shows glaciofluvial deposits and deltas, mostly composed of cobbles and boulders. Medium shading shows elevations
over 500 m and light shading shows elevations between 200 m and 500 m. (c) The elevations of prominent
glaciofluvial features projected on a simplified profile along Meta Incognita Peninsula. The western group
of glaciofluvial channels and deposits are located below 270 m and the water could therefore not drain
through the York canyons. The group located above 270 m can all have formed by water that drained
through the York canyons.
topographicallyasymmetric, with the main plateau at 660 to 720
m a.s.l. located close to the northeasterncoast. The northeastern
rim is high with numerous inlets, cirques, and short but deep
fjords and glacial troughs (Mercer, 1956). The central and southern part has a typical relief of 100 to 150 m, except for a few
deeper valleys, and slopes gently down from the plateau surface
to the Hudson Strait shore.
The inland area of Meta Incognita Peninsula is a mosaic of
glacially scoured zones with thin or absent till cover, and mature
subaerially weathered landscapes with few signs of glacial erosion. The latter, which typically occur on topographic highs, are
often covered with felsenmeer or sorted polygons. This mosaic,
with intricate boundary patterns, occurs in such low-relief areas
that it is highly unlikely to represent ice-cover/ice-free boundaries. We interpretthe nonglacial landscape component in such
mosaics as relict landscapes, markingthe locations of frozen-bed
zones (Kleman and Hattestrand, 1999). Most rivers draining
250
/ ARCTIC, ANTARCTIC,
AND ALPINE RESEARCH
Meta Incognita Peninsula run approximatelynorth-southin narrow valleys. The southern parts of some major valleys are glacially reshaped, while the northern sections often retain an entirely fluvial character with V-shaped cross-section and intact
spurs, testifying to limited glacial erosion of the inland zone.
No physiographic features in our field area are named on
official maps. To aid the reader in location, we have given informal names to some importantlandforms and lakes.
Results
TILL LINEATIONS AND GROOVED BEDROCK
The patternof till lineations and grooved bedrock on Meta
Incognita Peninsula is shown on Figure lb. On the southern
slope, lineations are essentially perpendicular to topographic
contours and the coastline. The northernplateauedge is intensely
FIGURE 2. The northwestern
York canyon, view looking southeast. The canyon depth in the
middle distance is 300 m, and
canyon width between rims is
around 600 m. The parallel
southeastern York canyon (not
visible on photo) is incised in
the plateau surface immediately
in front of the Terra Nivea ice
cap, which is visible on the skyline.
scoured, but well-defined lineation swarms converge on Leach
and Kneeland bays. No definite age constraintsexist for the lineation pattern, and it may well reflect the cumulative result of
several episodes of peninsula-centered ice caps. North of the
southern coastal zone on Meta Incognita Peninsula, no evidence
of a coherent lineation set related to northward-slopingice was
found. Striation data from the southern coastal zone (Kaufman
et al., 1993; Manley, 1995) show flow directions at approximately 180? angle to the direction that would characterize ice
caps centered on Meta Incognita Peninsula. Hence, there is a
possibility that some of the till lineations and grooves mapped
from airphotos indeed relate to northwardflow.
THE DRAINAGE ZONE
Most major north-south oriented interfluves on the south
slope of Meta Incognita Peninsula carry one or more washing
zones and associated coarse-grained glaciofluvial deposits suggesting interfluve-cutting ice-marginal drainage. In the eastern
part well-developed deltas are common, indicating open glacial
lakes (Straverset al., 1992). However, the glacial lake shorelines
cannot be traced over longer distances, making precise correlation of the various erosional and depositional features problematic. Collectively these glaciofluvial features indicate damming
ice in the south, and define a drainage zone that is nearly continuous from Shaftesbury Inlet to Noble Inlet. The altitudes of
the washing zones and glaciofluvial accumulations in the drainage zone are plotted in Figure Ic. They fall into two groups,
based on whether meltwater could drain through the York canyons or not. The drainage traces in the eastern group are located
high enough for water to have drainedthroughthe Yorkcanyons.
In contrast, the washing zones and boulder lag deposits in the
western group are located below the 270-m level. The meltwater
that formed these traces could not drain through the canyons,
and must instead have found other escape routes to the sea on
the south side of the Meta Incognita Peninsula. Airphoto mapping was conducted over more than 100 km to the west and
northwestfrom of the area shown in Figure lb, but no westward
continuationof the drainage zone was found (Kleman and Jans-
son, 1996). This is in agreement with the striae evidence for
northwardflow (Manley, 1995) which is also restricted to the
area east of Shaftesbury Inlet.
YORK CANYONS
The two major York canyons (Mercer, 1956; Blake 1966)
(Fig. lb, 2) cut right through the topographicbackbone of MIP.
Both canyons are approximately 20 km long and up to 300 m
deep. The whole of the southeastern canyon, and part of the
northwestern canyon, follow major tectonic lineaments. The
proximal and distal parts of both canyons have had valley precursors, as shown by valley-in-valley cross-profiles, but the central parts of both canyons appear to have been incised directly
in the undissected plateau surface. The threshold levels before
downcutting were around 520 m for both canyons. The thresholds are shallow cols interpreted as spillways. Given the evidence for high-level damming of water on the south side of the
peninsula, there is no need to invoke subglacial drainage for the
initiation of the downcutting, although we cannot rule this out
as a possibility. The floors of both canyons are masked by debris,
coalescent talus accumulations, and ponds, making a precise determinationof the bedrock threshold level difficult. On the basis
of a reasonable allowance of 10 to 30 m for debris accumulation
we estimate these threshold levels to have been in the range 270
to 300 m when the drainage occurred.
YORK AND HENDERSON INLET DELTAS
The massive York delta (Fig. 3, 4) was first described by
Mercer (1956) and is located immediately outside the canyon
mouths. It infills a large part of the fjord-like York Sound, and
also infills partly both arms of a significant northwest-southeast
valley which is the continuation of the inner arm of Jackman
Sound. The basic layout is simple, with a main terrace at 50 to
64 m elevation stretching over almost the entire 12 km length
of the delta. During Holocene uplift, the York River has entrenched itself progressively deeper towards its mouth. Two
groups of terraces occur at elevations above 50 to 64 m. The
J. KLEMAN ET AL. / 251
FIGURE 3. The distal part of
the Yorkdeltaphotographedfrom
105-m terrace at the mouth of a
tributaryvalley on the southern
side of the delta. The main terrace at 50- to 64-m elevation extends over the whole lengthof the
delta from the apex to the sea,
suggesting that the delta, and by
inference, also the Yorkcanyons
were largely formed during one
massive drainage event. The
distance to Frobisher Bay in the
background is 9 km.
highest terraces (105 m elevation) are located in opposing bedrock embayments approximately5 km from the apex of the delta. At the innermostpart of the delta a group of terracefragments
at 88 to 95 m elevation are perched along the bedrock walls.
The relation between the 88- to 95-m and 105-m terraces is not
entirely clear. The 88- to 95-m terraces may have formed a continuous surface that was eroded by the water flow during formation of the main 50-64-m level. However, the absence of any
terrace fragment at 105 m elevation at the innermost part of the
delta suggests that this level never extended west of the present
location. The 105-m terrace was searched for dateable material,
but only one shell fragment which yielded a modem radiocarbon
age was found.
A large boulder delta is located 7 km south of Henderson
Inlet, close to the eastern extremity of the TerraNivea ice cap.
The delta surface is similar in appearanceto the York delta, and
so large and coarse-grained that it cannot possibly be related to
the present meltwater drainage from the ice cap. The delta was
fed by meltwateralong two routes, which need not have operated
simultaneously.The westerly meltwater source can be traceduphill along a valley that is now hidden beneath the ice cap. A
markeddepression in the ice surface suggest that the valley continues to the southern side of the present ice cap. Meltwater,
presumably associated with the Henderson Inlet delta, was also
fed aroundthe eastern extremity of the Meta Incognita Peninsula
high plateau, with a washing zone at 420 m elevation leading to
a series of minor glaciofluvial deposits and, finally, the Henderson Inlet delta. We have been unable to resolve the role of drainage in this sector relative to the major drainage zone west of the
York canyons. The location of these meltwater traces suggests
that ice was "wrapping around" easternmost Meta Incognita
Peninsula, in line with the striation evidence and the presence
of ice-contact deposits (Miller et al., 1988; Straverset al., 1992;
Kaufman et al., 1993; Manley, 1995).
FIGURE 4. Map of
Yorkdelta. Light shading
representsthe main 50- to
64 m terrace and incised
parts of the delta. Medium
shading shows terrace
remnantsin western part
of the delta. Contourlines
for surroundinghills redrawnfrom 1:250,000 topographical map. Elevations for the delta surface are photogrametrically determined,with an
estimated uncertainy of
around 5 m.
252 / ARCTIC, ANTARCTIC, AND ALPINE RESEARCH
FIGURE 5. Glaciofluvial
features in the Deluge Lakes
area. A glacial lake northwest of Deluge Lake was incrementally lowered from
495 to around 335 m elevation. Only when the lake
level was between 495 and
approximately390 m could
the water drain throughMercer Canyon in the northeastern part of the map area.
DELUGE LAKEAREA
Field work was conducted in an area of unnamed lakes and
hills (Fig. 5), where abundantwashing zones and coarse-grained
glaciofluvial deposits can be followed over a distance of 9 km.
These features form a coherent zone linking a glaciofluvial gorge
north of Deluge Lake with the 4-km-long Mercer Canyon in the
east. The western (proximal) end of the zone has three entrance
points for the water, decreasing in elevation from west to east.
The highest entrance is at approximately 495 m elevation on a
flat stretch of a southward-facing spur. In a shallow depression
water flowed east and formed a series of coarse-grainedoutwash
deposits before entering the Deluge Lake depression, where similar deposits occur on the northernslope.
The second entrance point to the Deluge Lake drainage
zone is defined by a large glaciofluvial gorge with two intakes
cut directly into the plateau surface at approximately425 m elevation. It is located in a shallow col on a southward-facingspur.
Immediately outside the gorge is a 75-m-high boulder-and-cobble delta (Fig. 6). A shoreline inscribed approximately20 m up
the delta front shows that the level of the ice-dammed lake in
which the delta formed, lowered in at least two steps. The adjacent area to the east shows washed and glaciofluvially eroded
rock thresholds and coarse-grained glaciofluvial accumulations.
A third and minor point of entrance for water draining into the
Deluge Lake depression is defined by a lower channel cut at at
the southern extremity of the aforementionedspur.
Despite intense search and digging throughshallow till covers, glacial striae were only encountered at two localities in the
Deluge Lake area (Fig. 5). Both indicate ice flow towards the
south, compatible with flow of an ice cap centered on Meta
Incognita Peninsula. The shape of roches moutonn6es on a hill
south of Deluge Lake likewise indicated ice molding from the
north. No end moraines or other marginal accumulations that
could mark the marginal position of an ice readvance from the
south were found in the field area or detected in the airphoto
interpretation.The valley floors in the investigated area are generally devoid of glaciofluvial material.The boulder deltas on the
plateau and the upper slopes of the Deluge Lake depression are
_^^^^_
^^^^^^ f
FIGURE 6. The delta north of Deluge Lake has a delta front approximately 75 m high. The grain size in the
delta is cobbles to boulders. A shoreline inscribed at around 335 m elevation marks the lowest glacial lake level
in the western part of the Deluge Lake
depression.
J. KLEMAN ET AL. / 253
FIGURE 7. A summary of the evidence for northward ice flow and related ice-marginal positions on
the southern part of Meta Incognita Peninsula. Thick arrows show major meltwater routes. Striation data
(black arrows) are from Manley (1995). Numbers refer to meltwater traces and marginal positions discussed in text.
all morphologically intact, without evidence of postdepositional
disturbancesby overriding ice.
GEOGRAPHICAL EXTENT OF EVIDENCE FOR
NORTHWARD-SLOPING ICE
Figure 7 summarizes the collective evidence for northwardflowing ice impinging on Meta Incognita Peninsula during final
deglaciation. Northward-trendingstriae (Kaufman et al., 1993;
Manley, 1995) occur in a rather narrow coastal belt, but are in
good agreement with the ice margin outlines inferred from the
marginal drainage landforms. We have correlated the discrete
meltwater traces to reconstructedmeltwater routes, and we have
numbered them in stages. Stages 1 to 3 represent a logical deglaciation sequence, with successive retreat of the ice margin
exposing progressively lower drainage routes towards the York
canyons. Figure 8 visualizes the location of the ice margin during drainage through the York canyons. During stage 4, eastward-flowing water was unable to reach the approximately270
m elevation of the York canyons thresholds, and it must instead
have drained supra- or subglacially towards sea level on the
Hudson Strait side of Meta Incognita Peninsula. We are uncertain regarding the relation of the easternmost traces (stage 5) to
the main drainage zone fartherwest. It is conceivable that water
can have been fed by drainage from local glacial lakes in the
254 / ARCTIC, ANTARCTIC, AND ALPINE RESEARCH
area of the headwaters of the ProtecteurRiver, or alternatively,
that water was fed the main drainage zone. The latter scenario
requires that a long narrow marginal lake existed over the 50
km (south of Terra Nivea) which lack drainage traces. Such a
connection can only have existed before the York canyons were
cut down to their present depth, or alternatively, were blocked
by ice.
Discussion
The mapped drainage zone strongly supports the original
concept (Miller et al., 1988) of northward-flowingice on southeasternmost Meta Incognita Peninsula and across outer Hudson
Strait, but the ice-dynamic conditions during and immediately
before this event are less clear. The focal point of the disparate
pieces of evidence relating to the drainage event across Meta
Incognita Peninsula is the York delta. There is no doubt that
massive drainage through the canyons occurred during the last
deglaciation (Mercer, 1956; Blake, 1966; Muller, 1980). Whether
the canyons were partly cut during older drainage episodes
(Johnson and Lauritzen, 1995) is an open question. The 170-kmlong zone of boulder deltas and washing zones, the coastal northward striae and the shorelines indicating high-level damming of
water on the south side of Meta Incognita Peninsula, as well as
the dating of the York delta, all point to a northwardflow of ice
vt>_s
=:
, _a$$~~~~~~A
across the topographicgrain of the Hudson Straitdepression during the deglaciation.
CHRONOLOGICAL CONSTRAINTS
Manley (1995: Table 4-1) summarizes much of the dating
evidence pertaining to the Noble Inlet advance. The ice-contact
deltas at or near Noble Inlet fall in the range 8455 to 8860 14C
yr BP, while the age range for the York delta is 8620 to 8970
14C yr BP (Manley 1995). Hence, the age of the York delta,
which for its formation required damming ice and a meltwater
source to the south of the backbone of Meta Incognita Peninsula,
is relatively well constrained. There is some indication that the
Noble Inlet deltas are younger, which is consistent with the fact
that they must be related to a lower regional ice surface elevation
than that which existed during initial drainage through the York
canyons. The evidence for ice-free conditions in Hudson Strait
prior to the Noble Inlet event is not unequivocal. Jennings et al.
(1998) report single-shell mollusc dates >8.9 kyr and foraminifera dates in the 8.6 to 8.4 kyr interval from the EasternBasin
in Hudson Strait, and consider complete grounding in Hudson
Strait to have occurred only during the height of the Noble Inlet
advance at ca. 8.8 kyr. Gray et al. (1997), Lauriol and Gray
(1997), and Bruneau and Gray (1997) question the accepted
chronology of the Noble Inlet event. Numerous dates from the
interval 8.9 to 8.4 kyr (Bruneau and Gray, 1997), when the area
is supposed to have been ice covered, the absence of an oxygenisotope signal compatible with the concept of a readvance in
outer Hudson Strait,and the absence in Meta IncognitaPeninsula
tills of expected Quebec-Labrador erratic lithologies, caused
these authors to doubt that a massive surge or readvance occurred across outer Hudson Strait during the time interval 8.9 to
8.4 kyr BP Marine sediment data published by Kerwin (1996)
FIGURE 8. Oblique airphoto
of the southeastern York Canyon and the southern shore of
Meta Incognita Peninsula. The
ice-marginal position is based
on the glaciofluvial drainage
zone west of York canyons. The
lack of inland northward striations, marginal moraine deposits, and any traces of subglacial
northward drainage, suggests
frozen-bed conditions of Meta
Incognita ice during the acrossMeta Incognita Peninsula drainage event.
shows the presence of an isochronous "red bed" layer in Hudson
Strait, interpretedto mark the final drainage of glacial lakes Agassiz and Ojibway.
Barberet al. (1999) provide a revised chronology based on
core data from eastern and western Hudson Strait, calibrated
with a location-dependent reservoir-age correction. They indicate ice-free conditions in eastern Hudson Strait at 8.74 to 8.52
cal. yr BP, and western Hudson Strait at 8.65 to 8.42 cal. yr BP.
The final drainage of glacial lakes Agassiz and Ojibway postdates the opening up of Hudson Strait and occurred at approximately 8.47 cal. yr BP.
In summary,the dating evidence bearing on the Noble Inlet
advance is subject to some controversy. This makes it difficult
to resolve ice-dynamic conditions in Hudson Strait prior to the
drainage event(s) across Meta Incognita Peninsula. The inferred
duration of the Noble Inlet advance (readvance) is of the same
order as the potential errorsinherent in the dating technique. An
importantuncertainity concerns the reservoir age correction in
an area affected by a complex deglacial history and possibly at
times restricted contact with the open ocean. There is a possibility that oceanographicconditions were such that water masses
with different history, and hence reservoir ages, dominated in
different areas. The massive meltwater events, for which no
modem analog exists, may themselves have created such conditions. If this was the case, radiocarbonages may not be comparable and reconstructionsof retreatpatternsconsequently corrupted.
MORPHOLOGICAL CONSTRAINTS
The field evidence and our mapping of the landforms on
Meta Incognita Peninsula suggests that a credible reconstruction
J. KLEMAN ET AL. / 255
FIGURE 9. Interpreted conditions in outer Hudson Strait and
adjacent areas before and during
formation of the meltwater drainage zone on Meta Incognita Peninsula. (a) Supraglacial meltwater drains eastwards until reaching the ice margin or finding englacial or subglacial drainage
routes. (b) Enhanced ice flow
from Ungava Bay region raises
the ice surface in outer Hudson
Strait, forcing meltwater from a
large ablation area to drain over
a col on the deglaciated upland
on Meta Incognita Peninsula,
forming the York canyons.
of late-glacial ice dynamics in the area must be compatible with
the following observations:
RECONSTRUCTED SEQUENCE OF EVENTS
(1) The landform assemblage north of the zone of coastal
striations indicates that the inland parts of the final northwardsloping ice cover on Meta Incognita Peninsula was cold based.
We base this conclusion on the lack of northward-trendingstriae
in the Deluge Lake area, which is an area that was definitely
reached by northward-slopingice, and the absence of any evidence for subglacial drainage (no eskers present, strictly marginal drainage).
(2) A sustained very large flux of meltwater occurred and
was focused at a topographically unlikely place.
(3) The minimum ice surface elevation of northward-sloping ice on Meta Incognita Peninsula during formation of the
York delta was in the 270- to 520-m range. Consequently, ice
must have been grounded throughout the eastern basin in Hudson Strait (Jennings et al., 1998) during this event.
(4) There is no geomorphic evidence for deglacial northward flow west of Shaftesbury Inlet (Fig. 1). Meltwater landforms in this area suggest southward-sloping ice and a simple
patternof inland retreatof the ice margin (Kleman and Jansson,
1996; Manley, 1996).
The landforms in the drainage zone show a stepwise arrangement of successively lower drainage routes towards the
York canyons, and the whole zone forms a classic deglacial sequence. The coastal northward-trendingstriationsare fully compatible with an ice-margin outline suggested by our mapping the
drainage zone.
We favor a scenario where, prior to the drainage event
across the Meta Incognita Peninsula, the ice surface in Hudson
Strait was gently sloping to the east, possibly an ice stream in
an inactive state, centered over the deep west-east-trending eastern basin in Hudson Strait (Fig. 9a). The meltwater from a very
large ablation area was by the concavity of the ice surface focused and forced to flow east. Why was meltwater flux subsequently steered towards and across Meta Incognita Peninsula?
In our opinion the only reasonable mechanism is increased outflow of ice from Ungava Bay (Fig. 9b), in the mannersuggested
by Gray et al. (1997), raising the ice surface in Hudson Strait
and displacing supraglacial drainage to the north. An enclosed
supraglacial drainage basin may thus have formed in central
Hudson Strait, receiving meltwaterfrom a very large ice surface
area covering south-centralBaffin Island, western Hudson Strait
and northernUngava Peninsula. The basin would be infilled by
influx of ice from three sides, and hence, can only have been a
transientfeature.
We postulate the across-Meta Incognita Peninsula drainage
event to have been caused by an enhanced flow out of Ungava
Bay, most likely resulting in ice frontal advance at the mouth of
Hudson Strait, and a raised ice surface in outer Hudson Strait,
but with little effect on ice surface configuration farther west.
After this event, the calving ice margin probably quickly migrated westward in Hudson Strait, leading to the establishment
of marine conditions in the strait by 8400 14C yr BP. The extent
of downdraw of the ice surface in Ungava Bay and flow pattern
and conditions south of the Ungava Bay are difficult to determine. Modeling by Pfeffer et al. (1997) calls for basal sliding
associated with a large ice catchment to the south of Ungava
Bay, in line with conclusions by Veilette et al. (1999), but in
conflict with evidence for frozen-bed conditions of that area during final deglaciation (Kleman et al., 1994, Clark, 1999), and
the lack of erratics from the Labradortrough that such a flow
patternwould be expected to have produced (Gray et al., 1997).
The amount of geomorphological work achieved by the water cutting the York canyons is staggering. It is several orders of
magnitude larger than what was achieved by catastrophicdrainage of major glacial lakes in the Fennoscandian mountains
(Borgstrom, 1989) or the final drainage from the >350-km-long
Glacial Lake Naskaupi, which received meltwater from a wide
sector of the Quebec-Labradorice sheet remnant (Kleman, unpublished map data). Even if several episodes of canyon-cutting
occurred, and there is yet no specific evidence for this, the fluxes
during the last (or only) event must have been very large. This
is indicated by the more than 10-km extent of the main 60-m
delta level, and the coarseness (gravel to boulders) of the sediments in the proximal and middle parts of the delta. The source
of the water (2 above) is enigmatic. The highest washing zone
is at 495 m, and the initiation of York canyons was most likely
associated with damming up to 520 m. At those elevations, ablation per unit area must have been modest on the ice sheet,
calling for a very large ablation area feeding the drainage zone.
The lack of any traces of very large glacial lakes over 495 to
520 m elevation, and indeed the lack of suitable basins for such
lakes, indicates an entirely supraglacialorigin for the water that
cut the York canyons.
256 / ARCTIC, ANTARCTIC, AND ALPINE RESEARCH
Conclusions
The eastward-trendingmarginal drainage zone on southern
Meta Incognita Peninsula forms a conventional deglacial sequence, where drainage occurred at successively lower levels as
the ice margin retreated.The outline of the zone, and the damming of water north of it, require northward-sloping ice and
northward-directedice flow on southern Meta Incognita Peninsula. No northward-directedstriations or evidence of subglacial
drainage were found inland near the marginal drainage zone,
suggesting that the ice cover north of the coastal zone was coldbased.
A very large flux of meltwater across Meta Incognita Peninsula may have occurred because eastward supraglacial drainage on ice in Hudson Straitwas temporarilyimpeded and steered
northwardby a raised ice surface level in outer Hudson Strait.
This rise of the ice surface is interpretedto have been caused
by enhanced outflow of ice from Ungava Bay pushing into lowgradient eastward-slopingice in Hudson Strait.
Acknowledgments
This study was funded by grants from The Swedish Natural
Science Research Council to J. Kleman. We thank Dr. Sidney
Hemming for help during the fieldwork and Moses Naomi for
guarding against polar bears. J. Stravers, J. T. Andrews, and J.
Gray are thanked for constructive comments on the manuscript.
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J. KLEMAN ET AL. / 257