The Inst of Natural Sciences Nihon Univ Proc of The Inst of Natural Sciences Vol. 30 (1994) pp. n-22

Coastal Landforln and Radiocarbon Age of Cryogenic

Mounds Observed at Larsen Cove, Seymour ISland,

E ast of AntarctlC Penlnsula

Kunio OMOTO* (Received September 30, 1994)

Abstract. On the Larsen Cove. Seymour Island, east of the Antarctic Peninsula, cryogenic

mounds and ice-wedge casts have developed, with coastal terraces at several levels along

the coast. Five samples of algae were collected from marine sediments and radiocatbon dated

to estimate L0rmative age of the coastal landL0rm. The results of radiocarbon datings indicate

that the lower coastal terrace, 3 m a.h.t.1. was formed about 2,000-2,100y BP whereas the

cryogenic mounds. 0.5-1 m a.h.t.1. were formed about 1,200y BP.

d radiocarbon age ice-wedge Key words : Antarctic Peninsula, Seymour Island, cryogenic moLln ,

cast, coastal terrace

1 . Introduction

We investigated coastal landforms of Seymour Island (Argentina: "Isla Vicecomodoro Marambio")

when we took over a portion of The Japanese-Argentin Scientlfic Program 1) in 1987-1988 austral

summer season. In this paper, the present author reports on the coastal landform and formative

ages of lower coastal terraces and cryogenic mounds based on his field survey and radiocarbon

ages obtained from Larsen Cove, northeastern part of the island.

2. Outline of Laudfrom and Geology of Seymour Island

(1) Landform Seymour Island (64' 14/ 05//S ; 56' 43102!!W) is located about 80 km east of the Antarctic Peninsula,

and is surrounded by the Weddell Sea (Fig. 1). The island is about 22 km long, and 10 km

wide. To the southwest Snow Hill and to the west James Ross Island are covered with glaciers

or small ice caps whereas Seymour Island is ice free. Mean annual temperature of the island

is estimated -9.4~C (Corte, 1984) and the depth of permafrost at Larsen Cove, northeast of the

island is estimated 34 m deep (Fukuda et al., 1992). The island can be divided into two major geomorphic units : a prominent flat-topped plateau

called "Meseta", about 200 m a.s.1. and mountain or hill slope topography thyt is strongly eroded

* ~ ~c;~~'~~~~;~~~~~1~~;~~"~~~it-:~ Department 0L Geography, College of Humanities and Sciences, :j: 156 t~i ~1~~~~~~!J~7~3-25-40 Nihon University

25-40, 3-Chome, Sakurajousui, Setagaya-Ku, Tokyo 156, Japan

1) The Japanese-Argentil~o Scientlfic Expedition Study of the Islard Permafrost was organized in 1985 by Drs Masami Fukuda from the Low Temperature Science Laboratory of Hokkaido University, Sapporo, Japan, and Arturo E Corte from Centro Regional de Investigaciones Cientificas y Technologicas, Mendoza, Argentino. The first field survey was carried out

on Seymour lsland between November 1987 and January 1988.

Kunio OMOTO

58'w by ravines formed by meltwater streams, 56'

showing "badland topography" (Plate 1). The

, s~¥~ erosive effects of snow and wind are also ~6~~(¥ o strongly evident. On the gentle slopes around

e¥~e ~7 ' Meseta there are periglacial landforms such .*Cl~l

'~~¥ . .~) ~~ as gelifluction terraces and lobes, while on ' ~ Terror Gulf the flat ground ice-wedges (Plate 2), ice-wedge Erebus and

e4' Polygons, ice-wedge casts and cryogenic

James Ross mounds have developed. The cryogenic * seymour Island morphology of the island has been reported ~ Island

'/7 briefly by Corte (1984), Zinsmeister (1983) and (7S/ recently by Fukuda et aZ. (1992). wed d ell

l*land sea 50 k~

58'w 56'w (2) Geology Fig. I Location map sho According to Elliot et al. (1975) and wing the position of

Seymour Island. Zinsmeister (1982), the geology of the island ' characterized by Upper Cretaceous rs

(Campanian to lowermost Palaeocene) and fossili-ferous marine Lower Tertiary sediments (Palaeocene

to Upper Eocene). The former consists of sandstones and silty sandstones exposed on the southern

two-thirds of the island, while the latter consists of unconsolidated sand silty clay, clayey sand

and conglomerate outcrop around the Meseta at the north end of the island. The top of Meseta

is covered with Pleistocene glacial drifts, whose latest ones are considered to have been transported

by ice-bergs slightly before isostatic rebound of the island.

That there remains no glacial drifts except on Meseta suggests that they have been removed

fast because of long subaerial exposure and/or high rate of erosion. The existence of soft sediments

(Lower Tertiary) seems very significant for the formation of pennafrost and the development of

cryogenic landforms of the island.

3. Description of the Coastal Landfonu

Larsen Cove is a small inlet northeast of Meseta (Fig. 2). Between Larsen Cove and the

foot of the Meseta, a narrow coastal plain develops which is about 500 m wide (Fig. 3 and Plate

3). The landforms of the coast may be classified into four geomorphic units from mountain side

to the shore. They are coastal terrace, alluvial fan, emerged inter-tidal delta and a spit.

(1) Coastal terrace

Coastal terraces are found at several levels along the inlets or adjacent to small river mouths

up to 200 m a.s.1. (Plate 4). Zinsmeister (1980) reported on four terraces preserved on the gentle

slopes of Meseta in the vicinity of Cross Valley, west of Larsen Cove They are at 1-2 m,

4 m, 18 m and 135 m a.s.1. respectively. He assumed the top of Meseta might represent a fifth

terrace. Fukuda et al. (1992) reported on three marine terraces developed in different levels

at about 200 m, 50 m and 5 m a.s.1. respectively.

According to the author's field survey, the coastal terraces are classified into three groups

based on their altitudes. i.e. (1) higher terraces develop at 200 m (Meseta), 175-150 m and 135

-125 m, (2) middle terraces develop at 80-75 m (Sub-Meseta) and 50-25 m, and (3) Iower terraces

develop at altitude lower than 20 m a.s.1. The latest group is subdivided into eight geomorphic

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Coastal Landform of Seymour Island. Antarctic Peninsula

sunfaces whose altitudes are 1-2 m, 3 m, 5 m, 7.5 m, 10 m, 15 m, 18 m and 20 m a.s.1. respectively.

The present author focusses on the lower terraces in which he could observe sediments and

collect materials for radiocarbon datings. One of the lower terraces is ca. 3 m a.h.t.1.2) and consists

of stratified medium size sand beds, silt and clay layers, whose thickness is greater than 2.5 m,

and in which cross beddings and fossil algae layers were embedded (Plate 5). Two algae samples

(NU-083 and NU-084) were collected from ca. 20 cm and 60 cm below ground level for radiocarbon

datings.

A backshore terrace develop at about 50 cm a.h.t.1. and consists of 10 cm to 15 cm thick pebble

and sand bed overlying a fine marine sand bed. An algae sample (NU-080) was collected from

a medium size marine sand layer about 10 cm below ground level for radiocarbon dating.

(2) Alluvial fan Materials transported from ravines eroded by meltwater streams form small alluvral fan at

the entrance to the coastal plain (Fig. 3 and Plate 3). It is about 300 m long and its altitudes

is about 5 m a.h.t.1. at fan-head and about I m a,h.t.1. where it turns to the inter-tidal delta.

It continues on a new intertidal delta which is growing into a small inlet. In several places,

meltwater streams are dissecting original surface of the alluvial fan about 30 cm to I m deep

(Plate 7). The surface consists of sand, pebbles and gravels.

Numerous linearments and cracks develop on the alluvial fan (Plate 7), that have resulted

from the formation of ice-wedges, ice-wedge casts and thermal contraction cracks. The widths

of the ice wedge casts are between 50 cm and 80 cm and their depths are between 35 cm and

50 cm (Plate 6). Materials are fine to medium sand and pebbles.

(3) Emerged inte~tidal delta Between alluvial fan and the shore, there is a small emerged inter-tidal delta (Fig. 3 and

Plate 3). It is about 300 m wide and the altitude is between I m a.h.t.1. and O.5 m a.h.t.1. The

surface topography rs charactenzed wrth consprcuous mounds (Plate 8) termed "frost domes" by

Corte (1984), and "mudflat" by Zinsmeister (1976).

The mounds range in diameter from 2 m to 10 m, with spheroidal, quadrangular, or very

complicated patterns (Figs. 3, 4 and Plate 7). They resemble random ice-wedge patterns, or frost

mounds and earth hummocks in cross-sections although they have no vegitation. Around them

shallow troughs about I m to 3 m wide and 50 cm to I m deep have formed. The troughs

are sometimes filled with sea-water at high tide level.

In several places, circular depressions with shallow ponds were observed on the central part

of the mounds with maximum diameter of 3 m and a depth of 80 cm (Plate 9). The landform

resembles thennokarst subsidences those formed on the centre of pingos.

The materials of these mounds consist of 15 cm thick brown-black coloured mud over yellow

-orange/brown coloured stratified marine sand beds, about 20 cm thick and with cross beds (Plate

10). These in turn overlie dark-brown coloured marine sand bed thicker than 30 cm. One algae

sample (NU-081) was collected from one of the mounds. It was taken from about 15 cm below

ground level, where it was sandwitched between a dark coloured mud layer and sand bed.

2) meter(s) above high tide level. Altitude was determined temporary based on tidal observations at Larsen Cove. The daily

tide change was measured occasionally by the present author over a period of three weeks It showed about 320 cm between

high tide level and low tide level.

Kunio OMOTO

(4) Spit A small spit is now growing to northward

along the sandy coast (Fig. 3, 4 and Plate 3).

It is about 200 m long and about 40 m wide.

And the highest altitude is about 30 cm a.h.t.1.

It consists of sand and pebbles transported

from the southern sea-cliffs by longshore

currents which develop along the Antarctic

Peninsula.

4. Radiocarbon Ages

Five samples of algae were collected from

the coast (Fig. 4), and radiocarbon dated to

estimate formative age of the coastal landform.

Radiocarbon datings were carried out by the

author (Omoto, 1988), using a gas proportional

counting system of the Radiocarbon Dating

Laboratory of Nihon University. Geological

cross sections of each. sampling site and results

of radiocarbon datings are shown schematically

in figure 5 and Table I respectively.

Table I Radiocarbon ages of algae

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-084 '~~2;s

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WEDDELL SEA :¥ ~(~* ~~ r*+ *~Y ~NU-082

( o loo 200m e4'14'02"s +

collected f rom

Fig. 4 Locality map showing sampling sites for

radiocarbon datings, and distributions of

"cryogenic mounds". Contour interval is 1

m. The dotted lines indicate micro relief within

Im.

Larsen Cove, Seymour Island

1)meter (s) above high tide level, 2)corrected age based on modern standard

5. Discussions

(1) Reservoir correction

It is a well known fact that modern sea animals and plants living in high .latitude region

often indicate very old radiocarbon ages (Broecker and Olson, 1961 : Omoto, 1972). The phenomena

is explained as "reservoir effect" or "polar effect" and some figures or reservoir correction have f

been proposed (Omoto, 1983 : Stuiver and Braziunas, 1985).

One modern algae sample (NU-082) which was clearly washed ashore very recently was collected

from the strandline to estimate "reservoir effect". It indicated an age of 1,010lil80y BP (NU-

082). The figure doesn't contract with a figure of reservoir correction in Antarctica as reported

Coastal Landform of Seymour Island Ant rctlc Pemnsula

3m terrace

NU-083

~~~~ -- *

NU-084

cryo9enic Ino unds

j~i~~~~_ , '*_~,,.. backshore terrace , =~~i~~~,>*~*

NU-081 '~<:;}~~i.~~~'~'.~:~~~{,･.', .

NU-080 ~,, v mean tide level

NU-082

A B~f C~I DEI E~] ~ . ,*

Fig. 5 Schematic long-profiles of lower coastal terraces and cryogenic mounds

A : mud, B : sand, C : pebbles, D : algae layer, and E : sampling site for radiocarbon

dating

previously by Omoto (1983) and by Stuiver and Braziunas (1985). Based on the figure of modern

standard the present author subtracted 1,010 years from all radiocarbon dates obtained for reservoir

correction.

(2) Formative age of lower coastal terrace It is possible to estimate formative age of the lower coastal terrace based on the radiocarbon

ages of fossil algae sample. Two algae samples (NU-083 and NU-084) collected from 3 m a.h.t.1.

terrace indicated 2,080 t 90y BP and 2,780 i 120y BP respectively. These ages indicate that the

3 m terrace was formed at about 2,000-2,100y BP. Another algae sample (NU-080) collected

from a backshore terrace showed 570i70y BP. Therefore, it was formed ca. 500-600y BP.

The absence of organic materials for radiocarbon dating made it impossible to determine the

ages of higher coastal terraces.

(3) Formation of cryogenic mounds Many trenches and bore holes were made to detect ice layers at the bottom of troughs,

ice-wedge casts and at the central part of the "frost domes". Usually, pingos, frost domes and

ice-wedge polygons have ice layers or segregated ice layers inside. However, no ice layer or

segregated ice layer was discovered there. Permafrost layers appeared at about 50 cm below

the ground level. This means that the "frost domes" had not been formed originally as pingos

or ice-wedge polygons.

It is quite strange that there is no ice lens or segregated ice layer in and around the "frost

dome" although the inter-tidal delta should have rich groundwater compared with alluvial fan on

which many ice-wedges have formed. Based on the evidence the present author no longer consider

that they can be called "frost dome".

The problem remains as to what kinds of agents have worked and formed such mounds? Possible agents seems to lie in following : (1) prominent tide changes, (2) wind erosion, (3) erosion

due to meltwater streams, and (4) melting of ice particles stranded on the surface of the inter-

tidal delta.

All these agents seems to have worked under a periglacial environment since 1,200y BP.

Kunio OMOTO

It is likely that the variation in base level of erosion associated with daily tide changes is sufficient

for meltwater streams to be able to select and flow on the ice-wedges and cracks formed originally

on the inter-tidal delta. Then they cut down their channels onto the frozen ground and formed

wider troughs. Frequent braiding or meandering of meltwater streams would assist the process.

Corrasion and deflation would occur on the surface and at the margins of the mounds (Plate 11).

Based on these ideas and field evidences, the present author named the mound topography

"cryogen:ic mounds" 3) as against "frost dome" of Corte (1984).

Thermokarst-like subsidences seem to have been formed by melting of ice particles (brash

ice) stranded on the surface of the inter-tidal delta at the highest tide level. Such an event

was observed during the time in the field.

(4) Geomorphic development The existence of unconsolidated Lower Tertiary sediments allowed for fast dow'n cutting of

meltwater streams by summer runoff. In addition to the fast erosion, wind erosion and deflation

also played important roles in modifying the landforms of the island. As a consequence typical

"badland", erosional landfonns have developed around Meseta

Materials transported and deposited in shallow sea or enbayment formed the inter-tidal delta

or alluvial fans at the entrance to the coastal lowland. In some places north of Meseta, fluvial

terraces were formed by summer runoff. The glacial history of the island is still not clear. According to Smith (1985), bottom sediments

around the island suggest that they were deposited under floating ice within a low marine energy

or under the base of a floating ice shelf. The latter suggests that the ice shelf was much

extended at some former time, but the ages of extension and retreat of the ice sheet and ice

shelf are unknown.

Because of the fast erosion of its coastlines, Zinsmeister (1976) suggested the island is an

extremely young tectonic feature that has been uplifted only recently, although he could not determine

the age of the uplift.

The existence of coastal terraces developed at several levels indicate intermittent uplifts have

undoubtedly occurred. The radiocarbon ages determined by the present author made it possible

to estimate formative age of the lower coastal terrace. They suggest that postglacial uplift lasts

in this region.

6. Sununary

Based on the limited field survey conducted during the 1987-1988 austral summer season

and radiocarbon ages obtained from the Larsen Cove the present author can summanze the

geomorphic development of the Larsen Cove as follows

(1) In the Late Holocene, coastal terrace, 3 m a.h,t,1, was formed about 2,000-2,100y BP by

postglacial uplift.

(2) A spit was growing to the northward at Larsen Cove. Between the spit and the land,

dark-coloured fine materials transported by meltwater ~treams had deposited and formed a

inter-tidal delta.

') The term cryogenlc mounds should be used for mounds and/or domes that were formed originally under cold climatic envlronment when the general action o ice and freezing phenomena prevailed, f

Coastal　Landform　of　Seymour　Island，Antarctic　Peninsula

（3）Assuming　postglacial　uplift，the　inter－tidal　delta　emerged　at　about1，200y　BP．　Since　then，

　　formation　of　an　alluvial　fan　has　started．

（4〉In　a　periglacial　environment　and　under　prominent　daily　tide　change，meltwater　streams　have

　　fomed　chamels　or　troughs　on　the　su㎡ace　of　the　emerged　inter－tidal　delta．As　a　result，

　　conspicuous　mound　topography　named　“o叡go勉6規o観4s”have　been　formed。　In　contrast

　　on　the　alluvial　fan，ice－wedges　have　formed．

（5）Land　uplifts　continued　inte㎜ittently　and　backshore　terrace　was　formed　at500～600y　BP．

　　The　ice－wedges　formed　on　the　alluvial　fan　began　to　melt　and　ice－wedge　casts　were　formed．

（6）A　small　inter－tidal　delta　is　growing　in　front　of　the　alluvial　fan．　The　formation　of　the㎜al

　　contraction　cracks　and　periglacial　phenomena　still　continue　under　the　present　climate．

Ac㎞owle“gements

　　I　would　like　to　express　my　gratitude　to　Prof．Masami　Fukuda　of　Hokka孟do　University，a　leader　of

the　prolect，who　gave　me　an　opportunity　to　visit　Seymour　Island．　I　also　w玉sh　to　thank　aH　members

of　the　expedition，and　people　of　the　Vicecomodoro　Marambio　for　their　logistic　supports．Thanks　are　also

given　to　Prof・Jane　M・Soons　and　Dr，Ian　F．Owens　of　Department　of　Geography，University　of　Canterbury，

and　Prof，Eric　A，Colhoun　of　the　University　of　Newcastle　for　co㎜ents　on　this　paper．Another　thanks

are　given　to　Dr・Kunihiko　Kigoshi，Emeritus　Professor　of　Gakushuin　University　who　gave　useful　advice

in　sample　preparation，I　also　thank　Dr．」．Strelin，University　of　Cordoba，who　sent　me　several　photographs

of　the　Larsen　Cove，and　Mr．Alastair　Dyer，University　of　Canterbury，who　drafted　two丘g皿es．　This

study　was　suppo宜ed　by　a　scientific　grant　under　the　Monbusho（Ministry　of　Education），as　an　Intemational

Scientific　Research　Program（62041006）．

Re£erences

Broecker，W．S．and　Olson，E．196L　Lamont　radiocarbon　measurements　IV．R励06励oπ，3，176－204．

Corte，A，E．1984，Geocryogenic　morphology　at　Seymour　Island（Marambio）Antarctica＝A　progress　report．

　　乃z　4ごh　1窺召柳‘zだ07zαZ　Pε御zφン03オ　Co塵昭7z6θ　P706θθゴ碗g3．Fairbanks．192－197．

Elliot，D．H，，Rinaldi，C，，Zinsmeister，W，」．，Trautman，T．A。，Bryant，W．A．，and　Valle，R．1975．Geological

　　investigations　Seymour　Island，Antarctic　Peninsula．A班α7漉6Jioπ7π認げオhθU擁84S‘碗85，10，182　　－186．

Fukuda，M．，Shimokawa，K，Takahashi，N．，and　Sone，T．1992．Pemafrost　in　Seymo皿Island　and　James

　　Ross　Island，Antarctic　Peninsula　Region．Gθogア妙h此αZ　Rθ溺8ωoゾ議α餌π．65（Ser．A－2），124－131．

Omoto，K1972・A　preliminary　report　on　modem　carbon　datings　at　Syowa　station　and　its　neighbourhood，

　　East　Antarctica．z4π如παたR660rd，43，20－24．

Omoto，K1983，The　problem　an（i　significance　of　radiocarbon　geochronology　in　Antarctica．1π0伽θろR．

　　五．，諏耀3，R．P，醜ゴJiαgo，Ji．B．843．且窺α7め6Eαπh　S6’召π6召．Australian　Academy　of　Science，Canberra，

　　450－452．

Omoto，K1988。Radiocarbon　dating　reports　of　the　Nihon　University　No．L　P70‘88‘枷g3げオh6動3読漉θ

　　げNα魏r認S618π6θ3，Nガhoπ　Uπ掬8競な．23，86－88．

Smith，M，J，1985。Ma血e　geology　of　the　no貢hwestem　Weddell　Sea　and　adjacent　coasta1恥rds　and　bays　l

　　Implications　for　glacial　history，且η厩κ孟16Joμ7παZげオh8Uπ舵4S如‘85，20（5），85－86．

Stuiver，M，and　Braziunas，T，1985．Compilation　of　isotopic　dates　from　Antarctica．Rα伽cαめoη，27（2a），

　　117－304．

Zinsmeister，W，J，1976，Intertidal　region　and　molluscan　fauna　of　Seymour　Island，Antarctic　Peninsula、

　　且厩αr罐o　Joμ7ηαZげオh召　Uη舵4S如≠θ5，11（4），16－17．

Zinsmeister，WJ．！980，Coastal　teπaces　of　Seymour　Island，Antarctic　Peninsula．」4廠r砒語o鋸7πα1げ

　　診hθU航64S雄渉8s，14（5），16－17．

19 （！9）

　　　　　　　　　　　　　　　　　Kunio　OMOTO

Zinsmeister，W．J．1982．Review　of　the　Upper　Cretaceous－Lower　Tertiary　sequence　on　Seymour　Island，

　Antarctica，　』o解ηαZ　qブォhθGθoZog’6αZ　So6忽ッ五〇π40π，139，779－785．

Zinsmeister，W．J．1983．Unusual　periglacial　features　on　Seymour　Island，Antarctic　Peninsula．！生繊r6孟’c

　Jo％r澱Z　oヅ渉hθ　Uπ舵4S診α診θs，17（5），66－67，

（20）20一

Coas. tal I_andf()rm ()f Sevnl()ur I~land. Ant{lrc'tic I)enin~~ula

Plate l. Mes-~et;1 (prominent flirt-t,)1)1)ed x, urfact') and

c]issected mount{~in f)r hill ~51()pex,", vit'w~(1 fr()m we~t

coa~~t

Plate 2 ¥rl itt'-1Yt'(]~~(' ~.*)Ill (It'ttl~

r,)llll(} :It :~(lLltllhYt~t (If ¥1~st~til

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'-';~~='~~~"='-r'~_~-_~~~~~='~~i~'~~~~~'~~~~~~~~"' ' -~"~F'~~;~~~~' '"'<~~~~~~~~~~~~'~~-~#~~l' :~~~

-'~'~:i~i;:~~1"'-~-'-'--~~~~~~~~~~~~- '-~i~:_~-;'~~- T~~~~"- 'L t~ /1-~~-~~~:;~~~~;=~~ - - ~ ~~~~-" __~-_ __- _L_ _ ' ~ =~?~~'~~~1~~-~':- '~;1:~s~ = -';-+-~'+';: - -- == ~~:~ - -~~1~:~~~~~~~~~:~~if~i ;_~: _;; ; -i;;"It~:'~;~~~~~~~- ~~ ' "_ s'=~~_~~'~~~~;:;": ~:~~~:4~:L

*-^ ~~~~~~~~~L_*' = :;~~~~F~;~1;~r;1~~1:- ijT;: - - -_'-- - - - ~r ~t/__~i;~~'~:;!~ji~~#r~:~;;:1jl~iiZ:~;;~~J:~ji;jiiiii;:j~~~:::::i~::::~~::~~a!~~'~r';';'t::j}i~:j~t~j~~"~:

i~~ ~~~f ~' ~~ - '~'~~i~~~:1~~itf~~~~~~"~~-;"t~;:;~'~1

*:;~~~~~~"~~~"~-;~{"~;~{~~~'=~~;~'~~~:"~~~

-t'~~~~~~~~{s'~*'~t~*~~';~:_ +i: '~ ~ ~ ~ ~~T::i~~Fi'~?*'+~"r'-+**'**'~~~}~~~~'~~t~i

:, t~i l~:~~ll:IILI:~~~lI~I'~

: i~~:j

plate 3 1 ~lrsen covt' vie~ve( r()m le}~eta ~ spjt " -e - I f ¥ " (m]dd]e left) emerged inter ti( a] c e t'l an(1 L'rvt)~!en]c ' - l' I l( ~ ' mounds (upper mlddle) an allu¥'i'il fall (mlddl ~ l ' t ~ t e ()wer' dark col()red part three mountain pe~l '~;' {Ind br~iid~d k )*

l l river c~anne ~; are evident

Plate 4. Between h!1eseta (flat top) and Sub-Meseta (foreground), several flat surfilces are distinguished

Plate 5. Outcrop of 3 m a h t.1 coastal terrace, .ALlternations of sand, silt, and clay beds, (uPper) are

obser¥'ed. Two algae samples were c(rllected from c'a

~O cm and 60 cm below the ground level

*,**~~ '* *** ~~**' "*~ ** *'+"*+' *.* ** -, ' "**~* ***,**** "+ ~*"** ' * '*'~" ~ -' ' *' '*'*~*~=*~ji**i_,**'*_{~~t;:';:':'~;j:~;;;'~::{~;::,. . *,~;~~~~i-**:*==

* ' " j:~j*~:~*~'* _ _ _. ii* * ~ ~** * *~- * .

* **= * *.~i* ~~~ ~~ ~; * " ~'. ~~ *~;*** ^'~~'+*+* '~i =

+ _' * '*=*" * ' _' ' *+--~;~;~;~:~'*~(* * ~~i"' '~ '.' ' ~". ~' '=' ~ ~**~ * ~:"= ***:*; :~~;~~'~~=:1::'~;;+~;::~;~ ;i~:':~~' *' ': "

* ~**"***

Plate 6.

hammers) ()utcrop of an ice-wedge cast l.ength of a stake i_s about

(between two

60 cm

- 21 - ( 21 )

Kuni*, ()M( )'1'()

i*,~

Plate 7. ('n tht'

L;oh)re(]

dlxtinct

~~

,,~-*~~

~~' ' ~~* ~~

"~, 'sT_~~~ ' ~~:~ i~*' ~~:~ ~ s~~~~'f~'

~'~~;

An alluvial fill] (left) nn(1 f~n t'lllt'rX't'(] intt'r-1id{il

f(]rmt~r indicate ict'-wt'{ ~~e (dsts r~r;ii(It'(1 (lr~iinage 1

l'ilrt ()f left ul-]1)er) ('r}'()genic m()ul~(1~ (le¥'t'lop on

I]11(]t()~raphs" ~~'t'rt' t~tkt'n fr(_)m iLll iLirl)I~lnt' by Dr

(leltil iri~llt) I_inealnt'nt~~ (1('v('lr]1)

d~v~l[]1) ']rl the illluvi2li filll t(1ilrk

tht> t'nler~ed inter-ti(la] (leltil ~tr~ T ~;. ' t t't' I i n

l]late S. t'l]lL'r~t'(1

(' rv( )~t' I I i('

irlter-ti(l{ 1

lll( Iu n d s ( I t' v(' l( )1 ) ( rn t h ~

(lL,It~l

'~~~;~~ .J.1: ~~ -~F' .~

;~S$~fiF~~~~ii ' ~~ -

~~J~f~' -

plate 9' An example of sidence ()1)s"erved on the

therm()kars't-]ike sul)-

cry()~'enic mounds.

:: ~' ~ 'L: f~~~F~; "';F~: ' :1 rd 1~~IJ~' ~L~~~~i'~ -~ i~ ~ LS L~~~'~t4t:~! ~ ~ F;~h:;i{ ~1 *t~:~'~i ~~::!~:~; ¥1 Itj:' :;;~Y ~~::¥ r r ' ~ r L ~ LT~~~~S:"I~r~~I~

~ j! _t~ ~ '~'4 ~l~d'f~~

~ ¥" ~:: : h ~' ' 1~t~ ~;~ .~~ ~l ~~;s~~L ~~ ~~~;~~'~ I ~1 !T ~ ;;g{thSi

t I ~ _ ~t~~~ [ ~l:~~rl~~l~~;~ ~ #1

/ ?~ :~:f~ ' I H' ~ 1 :~~i ' ~"~~1~~~~~~'i~! IPI ~ ' ~ J'IP

' : I ~r ~i'l. 1 I~"~ ~1'~II' Pth '1';;:!:!J;',r:

~;.~; _ : :i- ~: L ~l FS

' ~: ~ ~' ~F~~~~~ l)late 101 All ()ut(In)1) of crv('~(]lli(1 In()L]ncl~

1¥l~iltl sai]11)le wfl~; (1()llected l)t'lT)w i]lucl 1~lVert

~~'1licl~ (]ver]i('s~ ¥'tlll()w-()ritln~fe c()1()ur'tl(1 ~si[n(1 beds

( 2? ) - ,, ,

.(r~}

Plate I l. ~.'L]1~f~lc't' ()f cry()~enic m()unds,~ ol)s, ervt'(1

{It tran~'iti()ll z()ne betwe(~n ('Int'rXTed inter-ti(lill

(lelta iln(1 illluvi{tl fitn ~.~tn)n~ {1~'ent~. of corra~'i()n.

deflation. an(1 wind erosion are (1estroying the surface ()f tll(' crvogenic m()ull(I~. Ileig_Tht ()f il

fielc] note i~ IXcTn.