Evidence for restricted ice extent during the last glacial maximum in the
Koryak Mountains of Chukotka, far eastern Russia
Lyn Gualtieri*
Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
Olga Glushkova
Northeast Interdisciplinary Research Institute, Far Eastern Branch, Russian Academy
of Sciences, 16 Portovaya Street, Magadan 685000, Russia
Julie Brigham-Grette Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
ABSTRACT
Field evidence in the Koryak Mountains–
Lake Mainitz region of far eastern Russia
supports three Pleistocene glacial advances.
The early Wisconsinan and pre-Wisconsinan
glaciations are represented by broad lobate
moraines extending as much as 30 km north
of the Koryak Mountains. Field evidence
demonstrates that the terminal, lateral, and
medial moraines, as well as meltwater channels, dead ice topography, kettles, and outwash plains mark the extent of ice during the
last glacial maximum (LGM), during which
glaciers reached no more than 20 km beyond
their present limits. Those emanating from
the southern Koryak Mountains may have
reached the Bering Sea. Numerical and relative dating techniques support these results
and test the theoretical models of the LGM in
western Beringia. Erratics on moraines and
glaciofluvial terraces, common to all valleys
at 13–13.8 m above river level, yield 36Cl exposure ages ranging from 10.08 to 25.78 ka.
The Koryak Mountains–Lake Mainitz record
of glaciation is spatially and temporally consistent with the glaciation pattern across central
Beringia found in other terrestrial and marine
records. Glacier growth in the Koryak Mountains was sustained by possible increased summer sea surface temperatures and precipitation in the northwest Pacific region. Evidence
from the northern Koryak Mountains (lat
64°N, long 177°E) indicates that the extent of
ice in western Beringia was limited to mountain
and valley glaciers during the LGM. This fieldbased research contradicts M.G. Grosswald’s
theoretical Beringian ice sheet hypothesis.
*Present address: Quaternary Research Center,
Box 351360, University of Washington, Seattle,
Washington 98195-1360, USA; e-mail: lyn4@u.
washington.edu
Keywords: Beringia, Chukotka, cosmogenic elements, erratics, glaciation, northwest Pacific.
Beringian Ice Sheet as proposed by Grosswald
(1998) and argues that the extent of ice during the
LGM in Chukotka was restricted.
INTRODUCTION
PREVIOUS WORK
The distribution of past glacial ice in Chukotka
(Fig. 1) is poorly known and controversial. One
hypothesis is that during the last glacial maximum
(LGM, ca. 20 ka) a single ice sheet covered the
entire Arctic Ocean and coalesced with ice caps
on Chukotka and other circum-Arctic landmasses
(Grosswald and Vozovik, 1984; Grosswald, 1988,
1998; Hughes and Hughes, 1994; Grosswald and
Hughes, 1995). This so called maximum model of
Arctic ice is unsupported by field evidence, yet
variations are commonly used in climate models
to illustrate global ice distribution during the last
glaciation (Peltier, 1994; cf. Kotilainen and
Shackelton, 1995; Hughes, 1996; Grosswald,
1998). Another hypothesis for the LGM in circum-Arctic areas is that ice was limited in extent
to mountain and valley glaciers, the Arctic Ocean
had a cover of sea ice, and glaciers extended a
minimal amount (to 20 km) beyond their present
margins (Hamilton, 1986; Kaufman and Hopkins,
1986; England, 1992; Brigham-Grette et al., unpub. data). The latter theory is supported by fieldbased studies and, in most cases, this research is
chronologically constrained by detailed stratigraphic work.
In order to test the two competing hypotheses,
our studies focused on the Koryak Mountains
(1062 m) as well as the Nahodka, Nygchekveem,
Gitgiveem, Rocamaha, and Lake Mainitz valleys
(Fig. 2). In addition, the stratigraphy along the
Cape Dionysia coastline (Fig. 2) was investigated. Field work was undertaken during the
summers of 1995 and 1996.
The purpose of this paper is to describe the
glacial history of the Koryak Mountains (lat
64°N, long 177°E) using modern chronological
tools to supplement existing Russian work. This
paper also presents field evidence opposing a
GSA Bulletin; July 2000; v. 112; no. 7; p. 1106–1118; 8 figures; 2 tables.
1106
The Bering Strait region has had a significant
influence on past Arctic climate change, especially with respect to changes in paleoceanographic and atmospheric currents and the migration of flora and fauna. Throughout the late
Pliocene and early Pleistocene, the BeringChukchi platform was alternatively submerged
and emergent due to fluctuations in sea level. The
last time the land bridge linked Asia to North
America was ca. 11 ka (Hopkins, 1959; Dyke
et al., 1996; Elias et al., 1996, 1997).
Although much field work has been done in
Alaska and other parts of eastern Beringia
(Fig. 1), western Beringia has remained unstudied in terms of modern, field-based, glacial
geology. Previous work by Russian scientists
(Arkhipov et al., 1986a, 1986b; Bespaly, 1984;
Ivanov, 1986; Glushkova, 1992) was based on
air photo interpretation and stratigraphic studies with limited field work in scattered locations. Most previous studies lack numerical age
control of the glacial history, with the exception
of radiocarbon age estimates on deposits associated with deglaciation.
Maps by Arkhipov et al. (1986b) that summarized the morphological type of late Pleistocene glaciation illustrated the Koryak Mountains as areas typical of valley- and cirque-type
glaciers. Bespaly (1984) concluded that the
Sartan glaciation (late Wisconsin equivalent) in
Chukotka was only half the size of the Zyryan
(early Wisconsin equivalent) and that Sartan
glaciers never extended beyond the foothills of
the Koryak Mountains. Glushkova (1992) suggested that the maximum extent of glaciation in
far eastern Russia occurred during the Zyryan
and that this penultimate glacial advance was
LAST GLACIAL MAXIMUM IN THE KORYAK MOUNTAINS OF FAR EASTERN RUSSIA
o
170o E
o
160 E
o
180
160o W
170 W
150o W
140o W
N
o
75 N
Arctic Ocean
East Siberian Sea
Wrangel Island
Beaufort Sea
70o N
Chukchi Sea
Brooks Range
Fig.2
Siberia
Chukotka
65o N
BS
Seward Peninsula
.
tns
M
ak
y
r
Ko
o
60 N
AK
2594
AP
Bering Sea
55 N
K105
chat
ka
Sea of
Okhotsk
s
nd
Kam
o
BG
RC14-121
RAMA44PC
RNDB-PC11
K119
V20-120
Aleutian
a
Isl
C
Gulf of Alaska
CB
Pacific Ocean
0
400km
Figure 1. Map of Beringia with place names. Core locations are marked in the Sea of Okhotsk, Bering Sea, and Pacific Ocean. BS—Bering
Strait; BG—Bering Gyre; CB—Cold Bay; AP—Alaska Peninsula; AK—Ahklun Mountains; and C—Cook Inlet. Study area and Figure 2 location are shown in the box. The area in gray is the Meiji drift. Heavy black arrows indicate dominant ocean circulation.
three times more extensive than the Sartan
glaciation. Glushkova (p. 339, 1992) concluded
that the snowline in Chukotka was 150–300 m
higher during the Sartan than the Zyryan
glaciation, although “there is still no prevailing
idea on the number of glacial epochs, character
and scale of glaciation, glacial geography, and
age boundaries.” Glushkova also interpreted the
Koryak Mountains–Lake Mainitz region as
characterized by valley glaciers (Glushkova, unpub. map).
The absence of glacial sediment as interpreted
by seismic transects across the Chukchi Sea and
northern Bering Sea (Fig. 1) by Biryukov et al.
(1988) indicate that the mountainous regions of
Chukotka supported valley and piedmont glaciers, and that these glaciers did not reach the
continental shelf during the last glaciation.
Mostoller’s (1997) moraine morphometric and
pedogenic study confirmed that ice was limited
during the last glacial maximum and that an
older, more extensive (mid-Pleistocene) ice
cover existed in the Tanyurer River valley
(Fig. 2) to the north of the Koryak Mountains.
This work is also supported by Heiser (1997)
who used satellite synthetic aperture radar
(SAR) to distinguish among glacial advances
throughout Chukotka.
Studies of the coastal stratigraphy were based
on sites scattered throughout Chukotka and were
undertaken independent of the inland glacial
morphology. Svitoch (1976) described a set of
marine and lagoon-estuary terraces at 50–60,
20–30, and 5–7 m above sea level (asl) in the
lower Anadyr depression (Fig. 2) ranging in age
from the mid-Pleistocene to the mid-Holocene.
The dating of the terraces is not well constrained,
but the sections may contain a combined record
of high sea-level events and glacioisostatic loading along this coastline. Our work on the dating
of the glacial landforms and sediments is compared with Svitoch’s original work on the terraces in an attempt to relate the coastal stratigraphy to the valley glacial history. A. Gasanov
(1969) studied more than 70 coastal sites on the
western Anadyr Estuary, Kanchalan Bay, and the
lower Anadyr River. He described various
glaciomarine units, noted the presence of mollusks, and logged the sedimentology; however, a
chronologically constrained stratigraphy was not
established. Studies by Brigham-Grette et al. (unpub. data) on the coastal stratigraphy to the north
of the field area, along the outer Chukotka Peninsula, indicate that the previous work by Russian
scientists is incomplete in terms of the sequence
and timing of marine deposits.
Palynological studies indicate that significant differences in the timing of vegetation and
possibly climate change across Beringia occurred throughout the late Quaternary (Lozhkin
et al., 1993). Lozhkin and Anderson (1995)
concluded from paleovegetation patterns in
Geological Society of America Bulletin, July 2000
northeast Russia that seasonal precipitation was
slightly greater and mean January temperatures
were as much as 12 °C higher than present during the last interglaciation. This conclusion
may help to explain why some ice advances
throughout the Pleistocene were significantly
more extensive than others. For example, the
increase in moisture availability at the end of
the last interglaciation may be a significant factor affecting the size and duration of Wisconsinan glacial advances and episodes. During the
transitional period between the LGM and the
Holocene interglaciation conditions, Betula
was dominant in eastern and central Beringia,
but was possibly absent from western Beringia
(Lozhkin et al., 1993). Although we know that
these changes occurred, we do not know why
they existed. What was the difference in climate
between western and eastern Beringia throughout the Pleistocene?
REGIONAL SETTING
Weather patterns in Chukotka are relatively
erratic due to the influence of the Arctic anticyclone, as well as the confluence of the Siberian
anticyclone and Pacific cyclone, particularly in
the Koryak Mountain region. The presence of
the Aleutian Low to the southeast also plays an
important role in delivering moist air to the region. Climatic records spanning 55 yr from two
1107
GUALTIERI ET AL.
o
o
170 E
175 E
boat, tracked vehicle, and/or on foot (Fig. 2). Terrace heights were determined by hand-leveling.
Equilibrium line altitudes (ELA) were determined
for comparison by three different methods: area
accumulation ratio (AAR) of 0.55–0.58, toe-toheadwall area ratio (THAR), and maximum elevation of lateral moraines (MELM).
ns
ai
t
un
o
Arc
tic
Cir
Ri
ve
r
cle
Ta
ny
ur
er
ul
k
Pe
y
ne
M
o
65 N
Amino Acid Analysis
Anady
r Riv
er
Krasneno
Lo
we
De
nad
yr
ssi
Anadyr
on
Anadyr
Estuary
r
ve
Fig.3 veem
k
he
gc
k
rya
Ko
lm
Ri
Anadyr Bay
N
gr KK
Ny
ins
ta
oun
Moraine Morphometry
Mrl
lp
Mt. and Little Dionysia
t = Tavavaim
cd = Cape Dionysia
gr = Gitgiveem River
lm = Lake Mainitz
KK = Kankaren Range
nr = Nahodka River
Meynypilgino
0
.
y Mtns
Zolota
t
cd
Velikaya River
nr
Kanchalan
Bay
rA
pre
100km
rl = Rocamaha Lake
lp = Lake Pekulneyskoye
Figure 2. The Anadyr region of Chukotka. Study area is marked in the box. Lakes are shown
in gray. Rivers are shown as black solid lines.
World Meteorological Stations near the study
area (Anadyr, 64.8°N, 177.6°E, and Markova
64.7°N, 170.4°E) provide mean annual temperature and precipitation data for the region. Mean
annual temperatures are –8 °C and –10 °C, respectively, and mean annual precipitation for the
two areas is 279 and 331 mm, respectively. Present snowline elevations on the northern and
southern flanks of the Koryak Mountains are
~600 and 380 m, respectively.
The study area is in a zone of continuous permafrost with abundant ice wedges in river bluffs.
The range of typical mean annual ground temperatures is –1 to –5 ° C (Brown et al., 1997). Near
Cape Dionysia (Fig. 2), sparse ground-ice bodies
with thermokarst complexes exist (Brown et al.,
1108
Amino acid geochronology was used to determine the relative age of marine mollusks in glaciomarine sediment with focus on whole valves of the
genera Astarte, following the rationale outlined by
Miller and Brigham-Grette (1989). Although Astarte are susceptible to the leaching of amino
acids (Roof, 1997), this was the most ubiquitous
and well-preserved species present in all samples. There were 75 analyses completed on Astarte from 16 samples along the Cape Dionysia
shoreline. Preparation of shells for amino acid
analyses followed standard techniques used in
many labs (Kriausakul and Mitterer, 1978;
Schroeder and Bada, 1976; Miller and Hare,
1980; Miller and Brigham-Grette, 1989; Mitterer
and Kriausakul, 1989).
1997). In the Koryak uplands, the permafrost is as
much as 100 m thick (Gasanov, S.S., 1969), but in
northern Chukotka thicknesses can be between
230 and 700 m (Brown et al., 1997). Two soil pits
at the top of the Cape Dionysia bluffs indicate active layer depths of 27 and 32 cm overlain by
18–32-cm-thick organic mats.
METHODOLOGY
Surficial Mapping
Study of Landsat images from 1972 and 1973
allowed the choice of field areas showing welldefined glacial landforms. Field areas were also
selected on the basis of accessibility by helicopter,
Geological Society of America Bulletin, July 2000
Moraine morphometric studies, following the
methodology of Kaufman and Calkin (1988) and
Peck et al. (1990), were carried out on all terminal
and lateral moraines. Measurements included distal and proximal slope angles, and crest width at
two or three sites per moraine. Kaufman and
Calkin (1988) concluded that average slope angle
is the best single distinguishing criterion and that
with just a few measurements, moraines can be
subdivided by relative age.
Soil Pedogenesis
Two soil pits, located on the crest and midslope, were dug on each moraine to compare
soil development from each slope position as
well as among moraines and terraces. Soil profiles were described and samples from each
horizon were collected for particle size analysis.
Soil age relationships were suggested by
Tedrow (1977) and Catt (1986).
Cosmogenic Nuclide Analysis (36Cl)
The premise in using cosmogenic isotopes in
the context of this paper is that glaciers erode,
transport, and deposit erratics that had previously been shielded from cosmic rays. When
the deposited rocks are uncovered, nuclides
such as 36Cl are formed during spallation reactions between cosmic rays and major elements
in the rock. We took 16 samples for 36Cl cosmo-
LAST GLACIAL MAXIMUM IN THE KORYAK MOUNTAINS OF FAR EASTERN RUSSIA
genic isotope analysis from erratics on moraines
and terraces. Ages reported in this paper are values obtained with the RICH (rock in situ produced cosmogenic-nuclide history) computer
program (Table 1). The program can incorporate as many as 100 pieces of data for each sample and can be used with multiple isotopes
(Dunne et al., 1996). RICH is available on the
Internet at http://primelab.physics.purdue.edu.
EVIDENCE FOR MULTIPLE
PLEISTOCENE GLACIATIONS
Kankaren Range
The northern side of the Kankaren Range
(Fig. 3) is marked by drift sheets from glaciers emanating from major north-south–trending valleys.
Erratics of green and gray quartzite and granite occur on top of a 201 m basalt high (Fig. 4B). Broad
lobate moraines extending to 30 km beyond (north
of) the eastern Kankaren Range are visible on both
SAR images and Landsat photos.
TABLE 1. NR/S CHLORINE RATIOS AND AGE FOR KORYAK
MOUNTAIN–LAKE MAINITZ SAMPLES
Sample
NR/S
(E-15)
Cape Dionysia
95CD1
96CD13
Nygchekveem River Valley
96NK19
96NK21
96NK25
96NK28
96NK29
96NK50
Nahodka Valley
96HD38
96HD39
96HD40
96HD41
96HD46
Lake Mainitz
96LM52
96LM53
Lake Rocamaha
96RM54
Error RICH age Error
(%)
(ka)
(%)
303.5 ± 11.9 3.9
298 ± 14
4.7
25.78
52.99
7.755
9.285
93.0 ± 5.5
98.7 ± 5.7
73 ± 10
46 ± 6
69.1 ± 4.7
42.7 ± 2.8
5.9
5.8
14
13
6.8
6.6
13.52
15.51
21.65
19.76
11.59
10.62
8.204
7.768
15.54
14.39
9.533
8.228
70.8 ± 4.5
90.1 ± 5.2
90.6 ± 4.4
87.3 ± 4.9
80.5 ± 4.1
6.4
5.8
4.9
5.6
5.1
14.72
15.87
16.65
14.71
15.99
8.156
7.74
6.986
7.632
7.2
57.5 ± 3.3
51.7 ± 5.3
5.7
10
10.08
19.51
8.39
11.61
91 ± 7
7.7
10.85
9.318
Notes: NR/S—the normalized radionuclide/stable nuclide ratio and
reported absolute error; RICH—rock in situ produced cosmogenicnuclide history.
Lake Mainitz
N 16km
Lake Mainitz is ~130 m deep, 16 km long, and
is in a graben to the south of the Kankaren Range
(Figs. 3 and 4B). The lake’s north-flowing outlet
is the Gitgiveem River, which drains into the
Nygchekveem River. The major inlets to the lake
are the Gitgipokeetkinveem and the Vorchin
Rivers (Fig. 4).
Geomorphology. Prominent landforms near
the lake include drift sheets from major tributaries (Fig. 4). The surface of one drift sheet, on
the east side of the lake, is composed of an 11cm-thick organic mat underlain by 24 cm of
loam. The drift sheets enter the lake and culminate at points where modern spits exist. These
spits are interpreted to be remnants of former
deltas that drained meltwater runoff and other
major glacial inflows into the lake. The spits to
the north and south of Toomani Island were likely
once connected to the island and have since been
eroded and reworked by modern processes. Conglomerate and sandstone erratics, as well as till
veneer, are present on the 268 m basalt high at the
northern end of the lake (Fig. 4B). Southnorth–trending meltwater channels on Toomani
Island and similar channels are cut into a lateral
moraine on the west margin of the lake. Ice
thickness in the Lake Mainitz basin was between
377 and 540 m, on the basis of ice modeling using the maximum elevation of glacial landforms.
The paleo-ELA of the glacier in this valley was
305 m, determined by the THAR (0.5) methodology and, more realistically, 500 m, based on
AAR (0.55) methodology.
Terraces. Two prominent terraces, 13.8 m
and 6.9 m above the present lake level, occur
KK
nk
nr
lm
rl
KORYAK
MTNS.
Lake
Pekulneyskoye
?
Bering Sea
Figure 3. Landsat image (taken October 4, 1972) of the study area. Black and white arrows
indicate former ice flow direction. Hachured lines indicate northernmost Sartan ice limit. A distinction is made between the valley glaciers emanating from the Kankaren Mountains (KK) and
those flowing north from the Koryak Mountain uplands; however, both are Sartan ice limits.
The question mark indicates ambiguity in the ice margin offshore. Ice extent lines were drawn
based on geomorphologic relationships and numerical age control. nk—Nygchekveem Valley;
lm—Lake Mainitz; nr—Nahodka Valley; and rl—Lake Rocamaha.
around the perimeter of Lake Mainitz (Fig. 4B).
The terraces are composed of silt and subangular to subrounded cobbles with varying lithologies. No soil development occurs on the terraces.
The continuous surfaces are dissected by channels and kettle ponds in some places around the
lake. Cosmogenic (36Cl) isotope analysis of
Geological Society of America Bulletin, July 2000
rounded cobbles on the 13.8 m terrace yields
ages of 10.08 ± 0.85 (96LM52) and 19.51 ± 2.27
ka (96LM53). Shells, or other dateable material,
above the present storm or driftwood mark are
not preserved around the lake.
Chronology and Interpretation. The drift
sheets, remnant deltas, erratics, and meltwater
1109
GUALTIERI ET AL.
132
240
200
731
200
131
172
173
istaya
Porog
Ri
ve
r
853
River
200
160
194
1048
542
Chernaya
Gi
tgi
po
ke
e
River
tki
nv
ee
m
619
899
904
772
Lake Rocamaha
843
10.85
183
195
578
254
358
Elevation (meters)
Terrace
Hangingvalley
Figure 4. (A) Geomorphology and
cosmogenic isotope ages and sites from
the Lake Rocamaha region. (B) Geomorphology and cosmogenic isotope
ages and sites from the Kankaren Range
and Lake Mainitz.
Erratic
Boundaries for areas encompassed by
terraces, moraine belt and drift.
19.51
0
36
Cl cosmogenic isotope age, ka
4 km
Contour lines in meters
channels suggest that the structurally controlled
Lake Mainitz basin was glaciated during the
LGM by a glacier flowing from south to north
and from the mountains on the east and west
sides of the valley. The terraces, formed during
a higher lake level, are cut into till. The till at
the northern end of the lake marks the extent of
1110
ice. We envisage glaciers spilling over from the
two main valleys feeding into the lake from the
east and west. The west valley ice was probably
an extension of the ice in the Nygchekveem
Valley. Although these valleys were not visited,
the kettled landscape is similar to the kettled
landscape to the north of the lake and suggests
Geological Society of America Bulletin, July 2000
that it has been glaciated. This hypothesis is
supported by the location of the spits, or remnant proglacial deltas draining the ice tongues.
The ice tongues from the east and west either
calved into a 13.8 m higher Lake Mainitz, or
converged with ice flowing over the lake basin
from south to north. This ice reconstruction is
based on lateral meltwater channels, the southnorth trough on Toomani Island, and the conglomerate and sandstone erratics on the 268 m
plateau on the northwest side of the lake. This
ice configuration fits with reconstructed ice elevations of ~500 m in the Nygchekveem Valley
and 500–530 m in the Lake Mainitz basin. The
undated 18.4 and 27.5 m terraces of the Gitgiveem River valley are interpreted to be
glaciofluvial, and composed of reworked till or
outwash material originally deposited at the
terminus of the glacier.
The chronology of the last glacial maximum
in this basin is based on two 36Cl ages on cobbles from the 13.8 m lake terrace. The ages are
minimums; however, the 10.08 ka (36Cl) date
may more accurately represent the age of the
13.8 m terrace. The 19.51 ka date probably represents inherited 36Cl in the rock. The younger
date of 10.08 ka can be interpreted two ways.
The first interpretation is that the 13.8 m terrace
level was occupied for 9.4 k.y. and that the two
dates represent different phases of terrace
growth. If this is the case, the lake level would
be 13.8 m higher until ca. 10 ka, when the lake
level then dropped to 6.9 m above its present
level. The absence of the 13.8 m terrace and the
presence of a continuous 6.9 m terrace surrounding the Little Mainitz basin suggests that
ice may have occupied that basin during the
13.8 m highstand, or between 19.5 and 10.0 ka.
The two modern spits separating the Big and
Little Mainitz basins are till or moraine remnants that previously dammed the lake, as ice
was occupying the Little Mainitz basin. As the
ice retreated, the lake level dropped to 6.9 m
above present. Coring the lake would help answer some of questions regarding the chronology of the lake levels. Work is presently being
done by P. Anderson and A. Lozhkin on two
nearby lakes, Lake Gitgikau and Patricia Lake.
The second interpretation of the 36Cl 10.08
ka date is that it is anomalously young, and that
the cobble had recently rolled, been frostheaved ~10 k.y. ago from its original position,
spalled, or weathered. Large, datable cobbles
were difficult to find on the terrace surface, and
some of the rock fragments from the best samples came from the sides of the rock that have
been recently exposed to surface deflation. Relatively recent exposure of the sides of the rock,
shielding of the lateral rock surface, or the edge
effect would explain an anomalously young age
(Zreda and Phillips, 1994; Dunne et al., 1999).
LAST GLACIAL MAXIMUM IN THE KORYAK MOUNTAINS OF FAR EASTERN RUSSIA
68
85
81
r
ve
Ri
52
m
e
ve
81
k
he
gc
Ny
73
77
96
88
63o 27′ N
122
97
201
283
264
200
If this were the case, the duration of the 13.8 m
lake highstand is unknown, as is the time of the
lake lowering to the 6.9 m stand.
Whether the ice advance from the south is
isochronous with the ice advances from the east
and the west of Lake Mainitz is uncertain. Detailed studies in the intervening valleys, the
Plaksivaya River (Fig. 4B), and the surrounding
mountains, as well as coring of the lakes, would
yield more definitive information. An investigation of the lowlands surrounding Lake Pekulneyskoye would also yield clues as to the glacier and/or marine interaction and sea-level
fluctuations along this coastline.
310
Rocamaha Lake
Gitgikau
Lake 103
613
752
800
256
386
489
Mt. Irvani
30
0
950
0
30 200
KANKAREN
RANGE
936
102
63o 23′ N
963
843
670
1059
140
164
559
184
20
0
30
144
0
834
tgi
vee
m
200
155
142
287
615
Riv
er
256
121
138
LakeMainitz
Lake Mainitz
300
952
213
477
293
Island
183
183
142
518
ley
Val
ift
Dr
200
654
241
Drift
121
Toomani
Toomani
Island
aya
ksiv
200
268
Pla
10.08
19.51
63o 19′ N
0
30
0
20
Gi
109
137
511
Dri
h
Vorc
412
ft
in R
121
iver
63 15 ′ N
o
0
20
Rocamaha Lake (Figs. 2 and 4A) is in a broad,
U-shaped, tributary valley of the Gitgipokeetkinveem River, the major inflow into Lake Mainitz.
Cirque floor elevations of four glaciers in the Lake
Rocamaha region range from 380 to 500 m. Proximal and distal slope angles on an unconsolidated,
fresh, cirque terminal moraine in this valley are
22° and 24°, respectively. The 36Cl cosmogenic
isotope analysis of the largest and most stable
boulder on the moraine yielded an age of 10.85 ±
1 ka (96RM54). Rock-glacierized moraines and
young cirques are present in the southern Rocamaha Valley, and three modern cirque glaciers
are actively calving into lakes within the valley. Paleocirque glaciers on the southern side of the Koryak Mountains (Fig. 2) most likely coalesced in
the broad Rocamaha Valley and flowed south toward Lake Pekulneyskoye and the Bering Sea
(Fig. 2). The ELAs for four modern cirque glaciers
in the basin range from 450 to 700 m, using the
THAR methodology. Paleo-ELAs are difficult to
determine and may not be useful on tidewater
glaciers, such as those on the south side of the Koryak Mountains that calve into the Bering Sea
(e.g., Paterson, 1994). At least one terrace occurs
in the broad valley to the northwest of Lake Pekulneyskoye. Bedrock-controlled terraces, which give
way to steep-sided scree slopes, surround the lake
in the northern part of the valley.
Chronology and Interpretation. The relatively fresh-looking landscape in the valley is indicative of Holocene glacier advance on the
northern and southern sides of the Koryak Mountains. The modern, low-elevation cirques in this
valley indicate that during the Sartan and older
glaciations, ELAs were lower than ~400 m, and
glaciers on the south side of the Koryak Mountains probably reached the Bering Sea. The relatively steep moraine slope angles and young 36Cl
cosmogenic isotope age of 10.85 ka serve as a
minimum age on deglaciation and moraine stabilization. Sartan ice most likely advanced out of
the Rocamaha Valley into the structurally controlled Gitgipokeetkinveem River and north into
500
121
283
203
591
176 30′ E
o
176 40′ E
o
B
176o 50 ′ E
Figure 4. (Continued.)
Lake Mainitz. This date is consistent with the
36Cl 10.08 ka date at Lake Mainitz.
Nahodka Valley
The Nahodka Valley (330 m) is a U-shaped
tributary valley at the southern end of the Nygchekveem Valley and close to the source of 600m-high modern cirque glaciers (Figs. 2 and 5).
The U-shaped valley is 1.0 km wide and surrounded by mountains that rise to 961 m on its
Geological Society of America Bulletin, July 2000
west side. Hanging valleys at 600 m elevation
connect with the main Nygchekveem Valley.
Lateral moraines and meltwater channels in this
valley occur at an elevation of 560 m, and former ice thickness is estimated to have been 250
m. Paleo-ELA, derived from cirques at the head
of the valley, is estimated to be 664–695 m asl.
The most prominent landform in the valley is
a 14.3 m arl (above river level) terrace that grades
to 13.8 m in the central part of the Nygchekveem
Valley (Fig. 6). Upvalley, the terrace measures 17
1111
GUALTIERI ET AL.
N
21.65
699
63o 11′ N
19.76
11.59
Elevation (meters)
183
776
Terrace
Hanging valley
227
13.52
15.51
235
Gladkoye Lake
Erratic
Boundaries for areas encompassed
by terraces, moraine belt and drift.
19.51
o
0
36
Cl cosmogenic isotope age, ka
1001
4 km
392
Ri
ve
r
63 08′ N
Contour lines in meters
697
0
30
Ny
gc
he
kv
ee
m
227
831
292
326
15.99
674
300
63 05′ N
866
293
291
ka Riv
Nahod
14.72
15.87
16.65
14.71
o
992
er
1180
362
450
63o 02′ N
Vos
to
6
ny R
592
1021
00
iv494
er
1221
KORY
A
K MO
1382
1065
579
Lake Adinokoye
UNTA
596
635
INS
1406
653
176o 15′ E
176o 22′ E
Figure 5. Geomorphology and cosmogenic isotope ages and sites from Nahodka valley and
upper Nygchekveem valley.
m arl and supports two small lakes. The terrace is
composed of a 10-cm-thick organic mat underlain by loam and cobbles to 25 cm in length. Four
large erratics (>3 m in length) from the surface of
the 14.3 m arl terrace were dated by 36Cl 14.72 ±
1.2 (96HD38), 15.87 ± 1.23 (96HD39), 16.65 ±
1.16 (96HD40), and 14.71 ± 1.12 (96HD41) ka.
Alluvial fans descend to an ~57 m arl flat surface that may be either an older terrace or outwash surface that was subsequently overrun by
ice during a later glaciation or a lateral meltwater
channel. A prominent boundary occurs between
this terrace and the 14.3–17 m arl terrace in the
Nahodka and Nygchekveem Valleys.
Chronology and Interpretation. The prominent 14.3 m arl terrace is interpreted to be
glaciofluvial and close to the ice source, as
shown by the abundance, angularity, and size of
erratic boulders and the presence of modern glaciers at the head of the valley. A reasonable age for
the 14.3 m arl terrace is 15 ka; this provides a
minimum age for the Sartan (late Wisconsinan)
deglaciation of valley glaciers retreating south
from the Nygchekveem Valley. The 1.9 ka difference in the 36Cl cosmogenic ages for the four
dated samples from the same terrace is attributed
to analytical variability.
1112
Nygchekveem Valley
Geomorphology. The Nygchekveem Valley is
one of the main meridional valleys in the northern Koryak Mountains and is adjacent to Lake
Mainitz (Figs. 2 and 7). The valley contains numerous lateral and medial moraines (Figs. 6
and 7), the surfaces of which are dissected by
meltwater channels, churned up by frost boils,
and vegetated with Pinus pumila. Six of the
largest, most stable, erratic boulders were dated
using 36Cl cosmogenic isotope analysis and
yielded ages ranging from 11.59 to 21.65 ka
(Table 1 and Fig. 7A). Slope angles for all
moraines average 6°. The uppermost elevation of
the moraines in the main valley is 350 m and to
460 m in the Temnay Valley, a west tributary valley. The elevation of the lateral moraines decreases steadily downvalley (south to north) to 90
m. Based on moraine height and glacier profiling,
a minimum estimate of ice thickness during the
LGM in the central Nygchekveem Valley was
200 m and as much as 230 m in the tributary valleys. The landscape in the Temnay tributary valley is dominated by kames, kettles, oxbow lakes,
meltwater channels, and an extensive outwash
plain. The paleo-ELA for the Nygchekveem ValGeological Society of America Bulletin, July 2000
ley ice system is estimated to be 500 m, based on
THAR (0.5) and 460 m based on AAR (0.58).
Gladkoye Lake is on the east side of one of the
widest sections of the Nygchekveem Valley
(Fig. 7A). Terraces, possibly representing a higher
stand of Gladkoye Lake, are incised into the hillside south of the lake. Evidence for a more laterally extensive ephemeral lake is indicated by a
faint, discontinuous washing limit a few meters
above and around the perimeter of the modern
lake. At the north end of the lake, a terminal
moraine (Fig. 7A) is composed of a silty matrix
with angular to subangular cobbles. The crest of
the moraine is dissected by meltwater channels
and supports kettle lakes. The lake is bounded by
equal-elevation moraines on the east and west
sides with average slope angles of 6.5°. Four erratic samples from the two moraines are 36Cl
dated as 11.59 ± 1.1 (96NK29), 13.52 ± 1.1
(96NK19), 15.51 ± 1.2 (96NK21) and 19.76 ± 2.8
(96NK28) ka. These dates provide a minimum age
range on the construction of the moraines and
hence, deglaciation of the Nygchekveem Valley.
The lateral moraine in the lower (north) Nygchekveem Valley also contains abundant kettles
and is dissected by meltwater channels to 75 m in
width that extend downvalley from the mountainside to the east. The crest of the moraine is undulatory and highly dissected by meltwater channels.
One erratic from a lower, flat, and more stable part
of the moraine was dated using 36Cl cosmogenic
isotope analysis as 21.65 ± 3.4 ka (96NK25). The
average slope angle on this moraine is 7°–7.5°.
A terminal moraine with a distal slope angle of
6° accessible from the Nygchekveem River occurs 17 km south of Gladkoye Lake. A 2-kmwide terminal moraine belt can be clearly seen 28
km downvalley from Gladkoye Lake (Fig. 7B) on
Landsat images, air photos, and 1: 25^000 topographic Russian maps. The moraine crest is 158
m in elevation and is marked by kettles, lakes,
and meltwater channels. Nearly 100% of the
moraine is covered by Pinus pumila, and erratics
on the surface were absent. A minimum 36Cl age
on one small (1.27 m) frost-heaved boulder is
10.62 ± 0.87 ka (96NK50). This boulder is interpreted as being frost heaved due to its low position in the ground and unstable position.
Terraces. Four terraces occur in the Nygchekveem Valley (Fig. 6). The lowest two terraces, at 1 and 4.5 m arl, are in the modern flood
plain and are composed of rounded cobbles,
pebbles, and sand. The 13–13.8 m arl terrace is
most likely Sartan in age, based on one 36Cl date
of 15.99 ± 1.15 ka (96HD46) as well as continuity in Nygchekveem and adjacent valleys
(Fig. 6). On the west side of the Nygchekveem
Valley a minimum height was obtained on a
prominent 15.4 m terrace consisting of a finingupward sequence of angular to subangular cobbles, gravel, coarse sand, and silty mud. We be-
LAST GLACIAL MAXIMUM IN THE KORYAK MOUNTAINS OF FAR EASTERN RUSSIA
700
Erratic
River or lake terrace
664-695
ELA
Lateral moraine
600
Melt water channel
Elevation, m
450-700
ELA
500
ELA
500
Hanging valley
460
ELA
*Terrace elevations are given as
meters above river or lake level
400
300
200
100
4.5
13-13.8
15.4
Riv
er
1
che
kve
odk
em
aR
iver
a
mah
oca
Lak
eR
Lak
eM
aini
tz
e
ang
nR
kare
Kan
57
13.8-17
3
Nyg
13.8
Nah
6.9
9.2
Figure 6. Intervalley correlation of major landforms in the northern Koryak–Lake Mainitz region. The dashed line separates drainage systems. Note the continuity of the ~13–13.8 m arl (above river level) terrace among valleys. This terrace is interpreted to be Sartan in age. The equilibrium line altitude (ELA) ranges from 460 to 500 in the two main valley systems (Nygchekveem and Lake Mainitz) and was determined by area
accumulation ratio method (0.55 and 0.58).
lieve this is correlative with the 13–13.8 m terrace. Due to the proximity of the terraces to the
ice source, most are composed of glaciofluvial
sediment and no material datable by radiocarbon
was found.
Soils. Nine soil pits were dug on moraines and
terraces in the Nygchekveem Valley. Five pits
were dug on the crests of moraines, three on the
midsection of moraines, and one on a terrace. In
general, the five soil pits on moraine crests contain a 4–9-cm-thick Oi horizon, a 10–22-cmthick Bw horizon composed of sandy loam, silt
loam, or loamy sand, and a BC or Cd horizon
composed of sand and/or cobbles to a maximum
depth of 53 cm. Although permafrost was not encountered in any of the crest soil profiles, organic
pods in the Bw horizon, variegated colors in the
BC horizon, and larger cobbles at the surface
were recognized. The cobbles at the surface are
believed to be due to frost heave, and in general,
the abundance and size of the cobbles decreased
with depth down to the C horizon.
The soil profiles on the midslope (5°–15°) of
the moraines are characterized by an 8–18-cmthick Oi horizon underlain by a Bw or BC hori-
zon composed of loam, silt loam, or loamy sand
to 40 cm in depth. More cobbles were encountered in two of the midslope pits than on the crest
pits; however, one midslope pit did not contain
cobbles. The one soil pit in a terrace yielded a 5cm-thick Oi horizon and BC1 and BC2 horizons
of silt loam and medium to coarse sand, respectively. The soil pit in the lower Nygchekveem
Valley terminal moraine (28 km downvalley)
contained fewer boulders and cobbles than the
other Nygchekveem Valley pits, and also had a
redder (5YR 5/6) and more well-developed B
horizon. The increased reddening and decrease in
boulder content in the soil is due to the advanced
stages of soil development on this older, pre-Sartan surface. As noted here, erratics were absent
on the surface of the moraine as well, indicating
prolonged exposure of this surface to weathering,
erosion, and reworking.
Chronology and Interpretation. The numerical chronology of deglaciation in the Nygchekveem Valley is constrained by the five 36Cl cosmogenic dates (11.59–21.65 ka) on erratics on
moraines, and one date (15.99 ka) from the 13.8
m terrace upvalley. The relatively young and
Geological Society of America Bulletin, July 2000
anomalous 36Cl date of 10.62 ka on a frostheaved boulder on the moraine 28 km downvalley from Gladkoye Lake does not represent
the age of the moraine, but simply the age of the
frost heaving that exposed the boulder. We propose that the moraine’s soil profile, absence of
boulders, abundance of vegetation, subdued
topography, size, and distance from the ice
source are evidence for greater antiquity than
the moraines surrounding Gladkoye Lake. The
moraine 28 km downvalley is interpreted to be of
pre-Sartan and most likely of Zyryan age. Although we have no numerical control on the age
of this moraine, the moraine morphometry is
similar to terminal moraines in the Tanyurer
River valley to the north, which indicate Zyryan
or older ages based on 36Cl cosmogenic isotope
data (Gualtieri et al., 1997).
The Gladkoye Lake moraines and lower Nygchekveem Valley moraine mark the maximum
extent of the Sartan ice advance. The Sartan maximum extent most likely took place >15 ka. However, although the cosmogenic ages are usually
interpreted to be minimum dates on deglaciation,
they can be too old due to an inheritance of older
1113
GUALTIERI ET AL.
A
Elevation (meters)
183
Terrace
Hanging valley
63 23′ N
o
Erratic
Boundaries for areas encompassed
by terraces, moraine belt and drift.
36
Cl cosmogenic isotope age, ka
19.51
0
4 km
Contour lines in meters
143
258
ice
300
281
555
30
0
203
645
360
864
140
Ri
ve
r
63 19′ N
164
Ku
ve
ve
e
m
o
494
w
flo
150
479
174
261
Nygchekveem
714
River
230
63 15 ′ N
o
258
743
Lower Anadyr Depression and
Cape Dionysia
170
21.65
202
186
727
540
699
0
30
204
300
63 11′ N
o
776
13.52
15.51
680
227
19.76
11.59
260
176 15 ′ E
o
Gladkoye Lake
176o 25 ′ E
Figure 7. (A) Geomorphology and cosmogenic isotope ages and sites from the southern
Nygchekveem valley. Arrows indicate former ice flow direction. (B) Geomorphology and cosmogenic isotope ages and sites from the northern Nygchekveem valley. Note the kettled topography of the moraine belt. Arrows indicate former ice flow direction.
36Cl
then some of the older, or inherited, 36Cl will still
be present. For more discussion on the inheritance problem see Briner and Swanson (1998).
Because these erratics have not traveled far from
the ice source they may not have been sufficiently
eroded during glacier transport, and therefore the
oldest age may be too old to estimate the true age
of deglaciation. These ages correlate with ages of
the Sartan ice advance of the Tanyurer River val-
1114
Geological Society of America Bulletin, July 2000
(Briner and Swanson, 1998) inherited from
an earlier time in the rock’s exposure history. One
of the many assumptions inherent in using in situ
accumulation of 36Cl to determine exposure ages
of rocks is that the erratic has been “zeroed” of its
former 36Cl accumulation during transport in the
glacier. If a sufficient portion of the rock has not
been eroded, or stripped of ~0.5–1.0 m of its outside surface during transport within the glacier,
ley (Fig. 2), which is based on both cosmogenic
and radiocarbon age estimates (Brigham-Grette
et al, 1997; Gualtieri, 1997; Gualtieri et al., 1997;
Mostoller, 1997).
The central Nygchekveem Valley moraine morphometry contrasts with that of Holocene and
modern moraines in the Rocamaha and Nahodka
Valleys. This, in conjunction with the cosmogenic analyses, supports the pre-Holocene age of
the Nygchekveem Valley landforms.
The 15.99 ka 13–13.8 m arl continuous terrace
is interpreted to be a glaciofluvial outwash surface. The age of this landform further supports
the 15 ka age for the Sartan deglaciation.
The soil data collected from the midslope and
crest pits differ in Oi and Bw thickness. In general, profiles on the midslopes had thicker horizons, as would be expected, due to aggradation of
crest material on the slope. The contrast between
the soil profiles, in general, from the Sartan-age
central Nygchekveem Valley moraines with the
Zyryan Nygchekveem Valley moraine 28 km
downvalley is supplementary to the morphometric data and further supports the restricted extent
of the Sartan glaciers.
The lower Anadyr depression (Fig. 2) is composed of numerous small lakes and rivers that
drain either into the Velikaya River or directly
into the Anadyr Estuary. The highest point in the
area is Mount Dionysia (577 m). Erratics are present in a stream on the western side of the mountain, and till, composed of subrounded quartzite
boulders in sandy silt, is present on the east face
of the 150-m-high Little Dionysia Mountain (informal name), which is a smaller peak a few kilometers east of Mount Dionysia.
Gullies in coastal bluffs south of Cape Dionysia
are dominated by till, which includes striated clasts
to 35 cm in length. In addition, erratics to 1 m in
length occur on the modern beach at the mouths of
the gullies. Stratigraphically below the till, shell
fragments and whole valves are found up to 11 m
asl in massive fine-grained silt interbedded with
sand and containing two pebbly layers. About 2
km north of the cape, striated (170°–190° orientation) and gouged basaltic bedrock is exposed on
shore, but shells are absent in the bluff sediments.
Terraces at 50–60, 20–30, and 5–7 m asl as initially described by Svitoch (1976) are not easily
discernable; however, we measured 70, 22, 11, and
6.5 m terraces using a digital altimeter (±1 m).
Two samples were taken for cosmogenic isotope
analysis from basaltic bedrock between the mountain and the bluffs. These yielded 36Cl ages of
25.78 ± 2 (95CD1) and 52.99 ± 5.2 ka (96CD13).
A. Gasanov (1969) described glaciomarine
units to 16 m thick with mollusks, gravel layers,
LAST GLACIAL MAXIMUM IN THE KORYAK MOUNTAINS OF FAR EASTERN RUSSIA
84
85
97
102
eem
ekv
er
Riv
gch
63 30 ′ N
o
Ny
291
99
93
260
10.62
232
Moraine belt
158
408
445
133
63o 26′ N
283
106
ice flow
ice wedges, and laminated sand and silt to the
north and south of Cape Dionysia; however, no
chronological control is available for measured
sections. We revisited the area in 1995 and 1996,
logged sections, and collected mollusk samples
for radiocarbon age determination and amino acid
geochronology: 75 analyses were completed on
Astarte from 16 samples along the Cape Dionysia
shoreline (Fig. 2). Average total ratios of aIle/Ile
are 0.042 ± 0.017, indicating a realistic age range
between 71.7 and 96.3 ka, based on modern permafrost temperatures in Anadyr. Radiocarbon age
estimates on the two individual shell samples with
the lowest aIle/Ile ratios (0.026 and 0.020 total)
yielded infinite ages of >49.9 ka and >45.2 ka
(AA25668 and AA25669). This chronology is
consistent with Svitoch’s (1976) TL date of 66.7
± 7.4 ka on a 50–60 m terrace south of Cape
Dionysia.
Chronology and Interpretations. The 36Cl
cosmogenic data from bedrock on the Anadyr
lowland suggest that this area has been exposed,
or ice free, since at least 52.99 ka, and most
likely longer. Pre-Sartan (pre–late Wisconsinan)
ice crossing this peninsula probably came from
the 1012-m-high Zolotay Mountains (Fig. 2)
and flowed south-southwest across the peninsula. The age of the glaciomarine unit on the
Cape Dionysia shoreline as inferred from amino
acid and radiocarbon data suggests that since
71.7–96.3 ka this coastline has remained free of
glacial overriding, glacially derived sediment,
and raised marine deposits. The numerical age
for the glaciomarine unit places it in the
Valkatlen interglaciation (stage 5 or Kazantsevo
interglaciation as defined in Siberia). The absence of raised marine deposits due to glacioisostatic loading of the crust on this and other
Chukotkan or Bering Strait Island coastlines
(Gualtieri, unpub. data; Brigham-Grette et al.,
unpub. data; Brigham-Grette and Hopkins,
1995) precludes the existence of a marine-based
ice sheet in the East Siberian Sea, the Arctic
Ocean, Bering Sea, or Bering Strait during the
last glacial maximum. Theoretical calculations
and arguments for abandonment of a marinebased ice sheet model were discussed in Heiser
(1997).
Data and field observations from the Cape
Dionysia coastline, coupled with the geomorphology of the northern Kankaren Range, indicate that
ice from the south, or Koryak uplands, did not inundate the lower Anadyr depression or the Cape
Dionysia coastline during the last glacial maximum. The Kankaren Range drift sheets extending
1.0 km beyond the present mountain front, as well
as the presence of till on the local basalt high, represent the extent of the LGM (Sartan). The
moraines visible on the SAR and Landsat photos
mark the extent of a pre-Sartan glaciation. The
presence of thick permafrost close to the surface
472
171
205
131
316
136
124
0
20
300
B
171
132
143
176o 15′ E
176o 15′ E
Figure 7. (Continued.)
in the lower Anadyr depression is consistent with
the hypothesis that this area has remained ice free
throughout the Sartan interval.
CORRELATION WITH THE LGM
IN ALASKA AND OTHER PARTS
OF RUSSIA
The restricted ice extent and age span of the
LGM in the Koryak Mountains–Lake Mainitz region is compatible with the regional climatological regime for Beringia. Ages for deglaciation
and ELA estimates for areas that share the
same primary moisture source as the Koryak
Mountains are shown in Table 2 and Figure 8.
The only other 36Cl-based chronology in the
region is that of Briner et al. (1998) for the
western Ahklun Mountains, Alaska. The other
numerical chronologies are mainly based on
14C ages from fluvial or glaciofluvial terraces
associated with the LGM. The methodology of
ELA determination is not consistent among researchers; therefore, if a method other than
area accumulation ratio (0.6–0.65) was used,
that is indicated in Table 2.
The chronology of the LGM and deglaciation
in the Koryak Mountains is regionally consistent.
However, local variations within mountain
ranges (north vs. south) could have been very
large, as shown by the variation in ELA lowering
or absolute elevation. The style of glaciation during the LGM was also similar in western and
southwestern Alaska and far eastern Russia. In
general, glaciers were cirque, valley, or montane
in character and reached no more than 20 km beyond mountain fronts. No evidence was found
Geological Society of America Bulletin, July 2000
for land or marine-based ice sheets coalescing
with terrestrial domes, as proposed by some (e.g.,
Grosswald and Vozovik, 1984; Grosswald, 1988,
1998; Hughes and Hughes, 1994). The minimum model of ice extent is consistent with anthropological and vegetation interpretations for
the Bering land bridge during the LGM (Ager,
1982; Elias et al., 1997). Diatom assemblages
(core RC14-121, Fig. 1) suggest year-round sea
ice cover in the Bering Sea during the LGM,
thereby precluding it as a viable moisture source
to feed large ice sheets (Sancetta et al., 1985).
In order to determine a robust chronology of regional paleoclimatic change, a numerical chronology must be established at smaller spatial intervals. Only two terrestrial numerical chronologies
for glaciation exist in central Beringia (Briner
et al., 1998; this study); however, as the number of
marine and lacustrine records in this region expands, higher resolution correlation with the
glacial geology is needed.
SPECULATION ON CORRELATION
WITH THE REGIONAL MARINE
RECORD
Scholl and Stevenson (1997) suggested that
the climate regime in Beringia is determined by
temperature, salinity, and the volume of surface
water exchanged between the Pacific Ocean
and Bering Sea. Therefore, the terrestrial and
marine paleoenvironmental records should be
consistent, and changes in terrestrial ice extent
should be reflected in marine records.
The proximity of the Koryak Mountains to
the 100 m Bering Sea isobath affords the op1115
GUALTIERI ET AL.
Core 2594
18
δ O (‰)
Last Glacial Maximum
5
29
30
31
32
33
34
35
17
modern
2594
Uvigerina auberiana
Northeastern Chukotka
Cook Inlet
Northern Alaska Peninsula
Gulf of Alaska
AK
KORYAK MOUNTAINS
Seward Peninsula
20
0-1
V2
AK
25
26
27
28
North-central Siberia
22
23
24
Aleutian Islands
16
17
18
19
20
21
2
West-central Alaska
THOUSANDS OF YEARS(14C)
13
14
15
2
Core V20-120
Summer
SST, oC
13
RAMA44PC
6
7
8
12
3
Neoglobigerina pachyderma sin.
4
5
9
10
11
4
1400
4 9
Uv.pa rvacastata
1
2
3
# IRD, g
0
Figure 8 The last glacial maximum (LGM) in the Koryak Mountains placed in a regional context and compared to the LGM in Alaska, other
parts of Russia, the northwest Pacific, and the Bering Sea. AK—Western Ahklun Mountains. See text (Table 2) for references on LGM data. The
δ18O record is from core 2594 (Fig. 1) as discussed in Gorbarenko (1996). The ice rafted debris (IRD) data are from Keigwin et al. (1992) and Gorbarenko (1996). Core locations are given for each data set and are shown in Figure 1. The lower and italicized IRD scale is from Gorbarenko’s
data, which were determined by visual estimation of the terrigenous concentration in the >100 µm fraction, where 1—few; 2—rare; 3—common;
4—abundant. Keigwin et al.’s (1992) IRD data are based on the >150 µm fraction. Summer sea surface temperatures (SSTs) are from core V20120 (Fig. 1) and are based on foraminiferal variations using transfer functions (Morley et al., 1987; Heusser and Morley, 1997). The modern summer SST at site location V20-120 (12.5 °C, Heusser and Morley, 1997) is shown for reference and is indicated by the dashed line. The average summer SST for this site during the LGM is 13–14 °C (Heusser and Morley, 1997). This trend continues to the late glacial, as shown by Elias et al.
(1997), who reported higher than modern summer temperatures (11.5–13 °C) on the Bering land bridge 11 ka. The two parallel, horizontal dotted lines indicate times when summer SST in the North Pacific was higher than modern, at the height of the LGM in the Koryak Mountains as
well as other central Beringian locations. It is concluded that higher than modern summer SSTs and increased precipitation sustained glacier
growth in the North Pacific region during the LGM.
portunity of preservation of the terrestrial ice
extent changes in the regional marine record.
Other glaciated mountain ranges in Beringia
are adjacent to the continental shelf or the exposed Bering Land Bridge, and therefore, their
ice fluctuations are less likely to be reflected in
the marine record. Marine records from the far
northwest Pacific, the southern Bering Sea, and
the Sea of Okhotsk (Fig. 1) show evidence for
cooling during the LGM. Calving icebergs
from southern Koryak Mountain tidewater
glaciers emptying into the Bering Sea could
have been carried south by the counterclockwise-rotating Bering Gyre surface current (Fig.
1) and may provide a source for ice-rafted de1116
bris (IRD) found in some of the marine cores
described in the following. Sea surface temperatures during the LGM in the Japan Sea, the
northwest Pacific, and the Sea of Okhotsk also
provide clues as to the timing of large-scale climatic interactions and fluctuations among the
atmosphere, oceans, and continents.
Keigwin et al. (1992) identified an IRD (terrigenous sediment >150 µm) peak older than 15 ka in
core RAMA44PC (Fig. 1) from the Meiji Tongue,
far northwestern Pacific (Fig. 8). This peak is
consistent with light δ18O values in benthic
foraminifers (Keigwin et al., 1992). Keigwin et al.
(1992) stated that the glacial maximum was 14 ka
and that sea surface salinity between 13 and 12 ka
Geological Society of America Bulletin, July 2000
was lowered, which may have resulted from the
melting of mountain glaciers. Keigwin (1997) reported that modern circulation patterns suggest
that Beringia may be the source of the freshwater
event. Cores K-105, K-119, and 2594 (Fig. 1) also
contain light δ18O values at 12.5 and 9.3 ka as
well as an increase in CaCO3, signifying a change
in productivity and sedimentological regime
(Gorbarenko, 1996). This 12.5–9.3 ka event,
which also correlates with a high IRD (terrigenous
sediment >100 µm) peak (core 2594, Fig. 8), lowered surface water salinity and represents a cooling
signal in the North Pacific (Gorbarenko, 1996). Although both Keigwin et al. (1992) and Gorbarenko
(1996) posed alternative mechanisms for the fresh-
LAST GLACIAL MAXIMUM IN THE KORYAK MOUNTAINS OF FAR EASTERN RUSSIA
TABLE 2. COMPARISON OF THE LGM, ELA, AND DEGLACIATION FOR CENTRAL BERGINGIA
Location
St. Lawrence Island
Aleutian Islands
Cold Bay
Alaska Peninsula
Western Ahklun Mountains
Northern Alaska Peninsula
Cook Inlet
Gulf of Alaska
West-central Alaska
Western Brooks Range
Seward Peninsula
Kuveveem River, central Chuktoka, Russia
North-central Siberia
Northeastern Russia
Southern Kamchatka, Russia
Koryak Mountains, Chukotka, Russia
LGM
(ka)
ELA
(m, asl)
150*
<25
26–24 and
20–17 36Cl
26–10
25–14
15–12
<34
24–15
> 11.5
400*
300*
Deglaciation
(ka)
>11
>11.5
>10
>16.9
18–12.2
12–10
300–400*
>11
200–400*
270
23
26–11
>15
11
Reference
Heiser (1997)
Thorson and Hamilton (1986)
Dochat (1997)
Detterman (1986)
Briner et al. (1998)
Stilwell and Kaufman (1996)
Schmoll and Yehle (1986); Hamilton (1994)
Molnia (1986)
Kline and Bundtzen (1986); Péwé (1975)
Hamilton (1986)
Kaufman and Hopkins (1986); Kaufman et
al. (1988, 1989); Peck et al. (1990)
Mostoller (1997)
Isayeva (1984)
Bespaly (1984)
Savoskul and Zech (1997)
This study; Glushkova (1992); Heiser (1997
600
460–500, 400–550,
15
and 450–600
Notes: LGM—last glacial maximum; ELA—equilibrium line altitudes. ELA determination methods other than area accumulation ratio (AAR) (0.6–0.65):
Detterman:cirque floor elevation; Kaufman and Hopkins:toe-to-headwall (0.4); Savoskul and Zech:mean elevation of lateral moraine and AAR;
Glushkova:Gepher’s formula and cirques; this study:AAR (0.55 and 0.58). asl—above sea level.
*Indicates amount ELA lowered from modern.
water source, the Koryak Mountain glaciers could
have contributed to the IRD record.
Figure 8 highlights times in the past 25 k.y.
when summer sea surface temperatures in the
northwest Pacific were higher than modern.
These times bracket the LGM in the Koryak
Mountains, other parts of Russia, and Alaska. Increased summer sea surface temperatures coupled with the increased summer precipitation
may have provided the moisture to sustain Koryak Mountain glacier growth during the LGM.
CONCLUSIONS
Field evidence exists for three Pleistocene
glacial advances in the Koryak Mountains–Lake
Mainitz region. This conclusion is consistent with
Heiser’s (1997) work based on SAR imagery for
the Chukotka Peninsula. The Zyryan glaciation is
represented in the Nygchekveem Valley only by
the downvalley moraine. A pre-Zyryan glaciation
is postulated for the age of the broad lobate
moraines extending as much as 30 km north of the
eastern Kankaren Range. The most well-preserved
evidence for glaciation in the Nygchekveem and
Lake Mainitz Valleys is of the Sartan glaciation,
with a maximum ice advance in both valley systems >15 ka. This is based on geomorphology and
numerical data. Reconstructed ELAs for the LGM
are 460 m in the Nygchekveem Valley and 500 in
the Lake Mainitz basin based on AAR. A continuous terrace, 13–13.8 m arl and dated using 36Cl
cosmogenic isotopes, is correlated between valleys, and clearly relates to the Sartan deglaciation.
The higher terrace in the Nahodka Valley (57 m)
although undated, is evidence for an older glaciation in this region.
The Koryak Mountains–Lake Mainitz record
of glaciation is spatially and temporally consis-
>5
tent with the glaciation pattern across central
Beringia. Higher than present sea surface temperatures and increased precipitation in the northwest Pacific region during the LGM may have
provided the moisture necessary to build and sustain Koryak Mountain glaciers. This study provides direct field evidence against Grosswald’s
(1998) Beringian ice sheet hypothesis.
vided by PRIME Lab–Purdue University. Original ice-rafted debris data for core RAMA44PC
were provided by Lloyd Keigwin. This paper
benefited from discussions with Patricia Heiser
as well as formal reviews by Parker Calkin,
Thomas D. Hamilton, and Don J. Easterbrook.
ACKNOWLEDGMENTS
Ager, T., 1982, Vegetational history of western Alaska during
the Wisconsin Glacial Interval and the Holocene, in Hopkins, D.M., et al., eds., Paleoecology of Beringia: New
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about late Quaternary vegetation in northeast Siberia, in
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Margins: Magadan, Russian Academy of Sciences, Far
East Branch, Northeast Science Center, p. 63–70.
Anderson, P.M., and Lozhkin, A.V., 1997, The late Pleistocene
Interstade (Karginskii/Boutelleir Interval) of Beringia:
Variations in paleoenvironments and implications for
paleoclimatic interpretations: Beringian Paleoenvironments Workshop, Florissant, Colorado, Program and
Abstracts, p. 15.
Arkhipov, S.A., Bespaly, V.G., Faustova, M.A., Glushkova, O.Y.,
Isaeva, L.L., and Velichko, A.A., 1986a, Ice sheet reconstructions: Quaternary Science Reviews, v. 5, p. 475–483.
Arkhipov, S.A., Isaeva, L.L., Bespaly, V.G., and Glushkova,
O.Y., 1986b, Glaciation of Siberia and north-east USSR:
Quaternary Science Reviews, v. 5, p. 463–474.
Bespaly, V.G., 1984, Late Pleistocene Mountain glaciation in
northeastern USSR, in Velichko, A.A., et al., eds., Late
Quaternary environments of the Soviet Union: Minneapolis, University of Minnesota Press, p. 31–33.
Biryukov, V.Y., Faustova, M.A., Kaplin, P.A., Pavlidis, Y.A.,
Romanova, E.A., and Velichko, A.A., 1988, The paleogeography of Arctic shelf and coastal zone of Eurasia at the
time of the last glaciation (18,000 yr B.P.): Palaeogeography, Palaeoclimatology, Palaeoecology, v. 68, p. 117–125.
Brigham-Grette, J., and Hopkins, D., 1995, Emergent marine
record and paleoclimate of the last interglaciation along
the northwest Alaskan coast: Quaternary Research, v. 43,
p. 159–173.
Brigham-Grette, J., Mostoller, D., Gualtieri, L., Glushkova, O.,
and Hamilton, T., 1997, Limited glacial ice extent across
N.E. Russia during LGM: Evidence from the Tanyurer
River Valley, Chukotka: Geological Society of America
Abstracts with Programs, v. 29, no. 6, p. A110.
Brigham-Grette, J., Hopkins, D.M., Ivanov, V.F., Basilyan, A.,
Benson, S.L., Heiser, P.A., and Pushkar, V.S., 2000, Last
This research was funded by the National Science Foundation Office of Polar Programs grant
9423730 to Brigham-Grette entitled “Collaborative research: Pleistocene glacial ice cover and interglacial paleoclimatic history in the NE Russian
Arctic—Comparisons with Alaska.” The National Park Service, the Geological Society of
America, and the Department of Geosciences,
University of Massachusetts, also aided in financial support. We thank Alexi and Sasha Galanin
and the Science Research Center of Chukotka for
logistical support, as well as the Northeast Interdisciplinary Science Research Institute for assistance with customs and permits. Field assistance
was provided by David Korejwo (University of
Massachusetts). The National Snow and Ice Data
Center, University of Colorado, Boulder, provided historical Soviet temperature and precipitation data. Landsat images of the Koryak Mountains and Lake Mainitz were provided by the
Global Land Information System–U.S. Geological Survey EROS Data Center. SAR (satellite
synthetic aperture radar) images were provided
by Patricia Heiser and the Alaska SAR Facility.
Radiocarbon age estimates were determined by
the University of Arizona AMS Facility. The 36Cl
cosmogenic isotope chemical preparation and accelerator mass spectrometry analysis was proGeological Society of America Bulletin, July 2000
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1118
Geological Society of America Bulletin, July 2000