- Email: [email protected]
Extent and Timing of Quaternary Glaciations in the Verkhoyansk Mountains
Chapter 64
Extent and Timing of Quaternary Glaciations in the Verkhoyansk Mountains Georg Stauch* and Frank Lehmkuhl Department of Geography, RWTH Aachen University, Templergraben 55, 52056 Aachen, Germany *Correspondence and requests for materials should be addressed to Georg Stauch. E-mail: [email protected]
64.1. INTRODUCTION
64.2. VERKHOYANSK MOUNTAINS
The extent and timing of Quaternary glaciations in the Verkhoyansk Mountains have been debated since the beginning of the twentieth century. The remoteness of these vast mountain areas and harsh climate conditions has constrained Quaternary research for many centuries. The location of the mountain system at the eastern edge of the Atlantic-influenced Eurasian continent is a unique situation in which to study not only regional climate effects but also the influence of Quaternary ice sheets in the north of the continent. The Verkhoyansk Mountains stretch for about 1200 km from the Laptev Sea coast to central Yakutia in an s-shaped manner (Fig. 64.1). Maximum elevations of 2959 m a.s.l. are reached in the south-eastern part of the mountains, in an area known as the Suntar Chajata. However, in the northern parts, most summits are around 1400 and 2000–2200 m a.s.l. in the central part. Harsh climate conditions are characteristic of the area and the so-called ‘cold pole’ of the Earth is situated at the village of Oimjakon, which is just 100 km away from the eastern branch of the mountain system. The mean annual temperature is at most stations below 10 C with mean temperatures in January of 40 and up to 20 C in July. Present-day precipitation varies considerably in the area as a consequence of orographic effects. In the valley of the Lena River in the west of the region, climate stations record values of around 200 mm a year, while on the western side of the mountains up to 700 mm are recorded. On the eastern side of the Verkhoyansk Mountains, values drop again to 130 mm (Lydolph, 1977; Murzin, 2003). At present, only two parts of the Verkhoyansk Mountains contain glaciers. In the northern branch, some isolated glaciers with a maximum length of 3.5 km exist (Stauch, 2006). In the high parts of the Suntar Chajata, an area of more than 200 km is currently glaciated (Koreisha, 1991; Ananicheva and Krenke, 2005).
Early reports of past extensive glaciations have been made by several Russian researchers such as V. Obruchev and V.N. Saks in the first half of the twentieth century. However, detailed research on the extent and timing of the Quaternary glaciations began in the 1960s with the work of V.N. Kind, V.V. Kolpakov and A.P. Belova and several other scientists. This work resulted in different models of Quaternary glaciations in the Verkhoyansk Mountains. Most research has been undertaken in the central Verkhoyansk Mountains, especially in the valley of the Tumara River (Fig. 64.1). Small terminal moraines in the main valleys of the central Verkhoyansk Mountains and in the western foreland have been dated by Kind (1975) on the basis of their relative position as remnants of retreating gLGM (global Last Glacial Maximum; ca. 21 cal. ka BP, 18 14 C ka BP) glaciers and Early Holocene advances (Fig. 64.2). Three large terminal moraines in the western foreland have been dated by radiocarbon to 29–15 14C ka BP (Kind, 1975; Kolpakov, 1979; Kolpakov and Belova, 1980). According to Kind (1975), a further terminal moraine, marking an even larger glacial extent, dates to 33–30 14C ka BP. This moraine had been named Karginsk after the Karginsk Interstadial of the Siberian stratigraphy and had not been identified in other area of north-eastern Russia. Two more extensive moraines are only preserved as ground moraine with no terminal ridges at the surface. They have been attributed to the early part of the last glacial cycle and the previous glacial cycle (Kind et al., 1971; Kind, 1975). Several maps have been published in the past few decades regarding the extent of glaciations mainly during the gLGM. According to Grosswald and Hughes (2002), north-eastern Russia was completely covered by a large ice sheet with maximum ice thickness of more than 2000 m east of the Verkhoyansk Mountains. This ice sheet
Developments in Quaternary Science. Vol. 15, doi: 10.1016/B978-0-444-53447-7.00064-7 ISSN: 1571-0866, # 2011 Elsevier B.V. All rights reserved.
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FIGURE 64.1 The Verkhoyansk Mountains (the hatched box indicates the central Verkhoyansk Mountains: (A) Tumara River; (B) Djanushka River).
was part of a large pan-Arctic Ice Sheet covering most of the Arctic regions. This hypothesis has been rejected by several studies in recent years (e.g. Velichko and Spasskaya, 2002; Brigham-Grette et al., 2003; Svendsen et al., 2004; Spielhagen et al., 2005). Other reconstructions show mountain glaciations of much smaller extent (e.g. Arkhipov et al., 1986; Zamoruyev, 2004). However, all maps indicated glaciers with a length of more than 100 km on the western side of the Verkhoyansk Mountains stretching from the high mountain areas down to the foothills and out in the forelands. Research from the start of the twenty-first century, based on a re-evaluation of the morphological landforms in combination with IRSL (infrared-stimulated luminescence) dating of overlying aeolian sediments as well as glacial sediments, resulted in a different chronology of glaciations in the Verkhoyansk Mountains. According to these new results, glaciations in the central Verkhoyansk Mountains were either very limited or non-existent during the past 50 ka (Fig. 64.2). The last glaciation which left traceable morphological landforms occurred before 50 ka (Stauch et al., 2007). Terminal moraines (termed I; Fig. 64.3) related to this glaciation have been deposited
inside of the mountain system and are relatively small compared to older glacial landforms. These results correspond with studies from the Charaulach Mountains in the northernmost part of the Verkhoyansk Mountains close to the delta of the Lena River. This mountain chain has not been glaciated at least during the past 60 ka (Schirrmeister et al., 2002; Hubberten et al., 2004). Glacial deposits at the mountain front of the Verkhoyansk Mountains are generally much larger in size. In the Tumara River valley, terminal moraines (II) form impressive arcs with diameters of 20 km. Aeolian sediments covering these terminal moraines have been dated to 19.2 and 46.8 ka (Stauch et al., 2007) but on the basis of their relative position, the underlying glacial sediments were deposited prior to 50 ka. A third set of terminal moraines further downstream of the rivers is even larger. Similar glacial landforms can be observed in many river valleys in the western foreland of the Verkhoyansk Mountains. IRSL ages indicate formation around 80– 90 ka ago. At the Tumara River, one further terminal moraine is preserved (IV), while two more former glacier terminus positions can be reconstructed in the Djanushka River valley (IV and V). Preservation of both moraines is
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Extent and Timing of Quaternary Glaciations in the Verkhoyansh Mountains
879
64.3. REGIONAL COMPARISON
FIGURE 64.2 Extent and timing of glaciations in the central Verkhoyansk Mountains (grey: according to Kind et al., 1971; black: Stauch et al., 2007).
only sketchy as a result of fluvial erosion caused by the younger glacial advances and in the case of the outermost moraine V, the Lena River. According to the IRSL ages obtained from the Tumara River, moraine IV gives an age of 100–120 ka, while the sediments of the outermost moraine at the Djanushka River (V) have been deposited around 135 ka. However, only two IRSL ages are at present available from this moraine V (Stauch et al., 2007). Similar successions of terminal moraines have been mapped in several neighbouring valleys on the western side of the Verkhoyansk Mountains (Stauch, 2006; Stauch and Lehmkuhl, 2010). In contrast, terminal moraines on the eastern side of the mountains are smaller and closer to the higher part of the Verkhoyansk Mountains. Late Quaternary glaciers must have been much smaller on this side and all terminal moraines have been deposited inside the valleys of the mountains and not on the piedmont. These results indicate a primary moisture source from western direction during times of glaciations and, therefore, a similar situation as today. This is also confirmed by the orientation of cirques and cirque floor elevations. Nearly 500 cirques have been mapped in the central Verkhoyansk Mountains on the basis of satellite images. Cirques located at lower elevations are generally found on the western side, while cirques on the eastern side are 500 m higher. The average cirque floor elevation is around 1400 m a.s.l. (Stauch, 2006).
Comparing these results with recent studies from areas west and east of the Verkhoyansk Mountains shows some similar trends in the timing of glaciations but also some striking differences. Moisture-bearing winds from the west have been strongly influenced by development of the large ice sheets in the northern part of the Eurasian continent. Svendsen et al. (2004) reconstructed the extent of the Eurasian Ice Sheet for four time periods in the Late Pleistocene. The two segments of the ice sheet, the Scandinavian Ice Sheet and the Barents–Kara Ice Sheet, developed opposite trends (Svendsen et al., 2004; Chapter 28). While the western sector became progressively larger during this period, the eastern sector became smaller in size. The trend of the Barents–Kara Ice Sheet is therefore comparable to the development of mountain glaciations in the Verkhoyansk Mountains. This is further confirmed by the development of mountain glaciations in the Polar Urals (Fig. 64.4). An age of around 20 ka has been obtained for a terminal moraine only 1 km from the present ice margin, while moraines further away from the mountains have an age of 50–60 ka (Mangerud et al., 2008). A similar age has been given by Astakhov and Mangerud (2007) for river terraces related to glaciers from the Putorana Plateau. East of the Verkhoyansk Mountains, only few results concerning the extent and timing of Quaternary glaciations in the Russian Far East are available (Chapter 63). A recent summary highlighted two areas of more detailed studies, the Pekulney Mountains in the Anadyr Uplands and the Koryak Mountains (Fig. 64.4) on the eastern side of the Eurasian continent (Stauch and Gualtieri, 2008). Three suites of terminal moraines have been mapped and dated in the Pekulney Mountains (Brigham-Grette et al., 2003). The youngest of these sets has been termed the Kuveveem Moraines. Cosmogenic isotope dating revealed a formation during marine isotope stage (MIS) 2. Remnants of two older glaciations have been identified at the Tanyurer River. The upper moraine has been termed the Chumyveem moraine. Cosmogenic isotope dating of erratic boulders has yielded ages between 41 and nearly 70 ka. The second moraine (Anadyr River moraine) has been dated on the basis of morphological criteria. Brigham-Grette et al. (2003) assumed Middle to Early Pleistocene age for this moraine. In the Koryak Mountains, a study by Gualtieri et al. (2000) presented evidence for at least two Pleistocene glaciations. A younger glaciation occurred again during MIS 2, while cosmogenic isotope data from the lower Anadyr depression, north of the mountains, indicate a glaciation before 50 ka. No terrestrial evidence has yet been found relating to the early part of the last glacial cycle (Weichselian Stage). However, BrighamGrette (2001) and Brigham-Grette et al. (2001) suggested, on the basis of glaciomarine sediments, a rapid glaciation of Chukotka Peninsula directly after the last interglacial.
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Quaternary Glaciations - Extent and Chronology
I I
II II III III IV IV V
FIGURE 64.3 Terminal moraines in the Tumara and Djanushka valley (modified from Stauch et al., 2007).
FIGURE 64.4 Northern Asia and selected mountain areas.
64.4. CONCLUSION Quaternary glaciation in the central Verkhoyansk Mountains became more limited in extent throughout the Late Quaternary. The largest extent of ice has so far been attributed to the penultimate glacial cycle (Saalian Stage) prior to the Eemian interglacial. Further glaciations occurred at around 100–120, 80–90 and before 50 ka. It seems that there was no glaciation in the area during the gLGM
(MIS 2). However, whether the dated terminal moraines during the early part of the glacial cycle represent individual glaciations with a considerable ice retreat between, or whether they are remnants of glacier oscillations, remains one of the unanswered questions. The extent and timing of glaciations in the Verkhoyansk Mountains shows similar trends to mountain glaciations further west and the Barents– Kara Ice Sheet (Chapters 27 and 28). However, there have been more glaciations identified in the Verkhoyansk area
Chapter 64
Extent and Timing of Quaternary Glaciations in the Verkhoyansh Mountains
during the early part of the last glacial cycle. East of the Verkhoyansk Mountains, a different pattern is recognisable. In these areas, glaciation also decreased in size progressively through the last glacial cycle, but prominent terminal moraines were developed during MIS 2. The asynchronous formation of glaciers on the western and eastern slopes of the Verkhoyansk Mountains is the result of different moisture sources. In the west of the Eurasian continent, the growth of the Scandinavian Ice Sheet blocked the moisture-bearing air masses from entering the far east of Siberia and prevented the growth of glaciers in the Verkhoyansk Mountains during the MIS 2, despite very low temperatures. In contrast, on the easternmost side of the continent, moisture from the Pacific supported the development of glaciers in the Pekulney and Anadyr Mountains during MIS 2 (Stauch and Gualtieri, 2008; Stauch and Lehmkuhl, 2008). However, there are still large areas in north-eastern Russia with large mountain systems where no dating results for glacial sediments are available. Further research in this interesting area is still needed.
REFERENCES Ananicheva, M.D., Krenke, A.N., 2005. Evolution of climatic snow line and equilibrium line altitudes in the North-Eastern Siberian Mountains (20th Century). Ice Climate News 6, 3–6. Arkhipov, S.A., Isayeva, L.L., Bespaly, V.G., Glushkova, O., 1986. Glaciations of Siberia and North-East USSR. Quatern. Sci. Rev. 5, 463–474. Astakhov, V., Mangerud, J., 2007. The Geochronometric age of Late Pleistocene terraces on the Lower Yenisei. Doklady Earth Sci. 416, 1022–1026. Brigham-Grette, J., 2001. New perspectives on Beringian Quaternary paleogeography, stratigraphy, and glacial history. Quatern. Sci. Rev. 20, 15–24. Brigham-Grette, J., Hopkins, D.M., Ivanov, V.F., Basilyan, A., Benson, S.L., Heiser, P.A., et al., 2001. Last interglacial (isotope stage 5) glacial and sea level history of coastel Chukotka Peninsula and St. Lawrence Island, western Beringia. Quatern. Sci. Rev. 20, 419–436. Brigham-Grette, J., Gualtieri, L.M., Glushkova, O.Yu., Hamilton, T.D., Mostoller, D., Kotov, A., 2003. Chlorine-36 and 14C chronology support a limited last glacial maximum across central Chukotka, northeastern Siberia, and no Beringian ice sheet. Quatern. Res. 59, 386–398. Grosswald, M.G., Hughes, T.J., 2002. The Russian component of an Arctic ice sheet during the Last Glacial Maximum. Quatern. Sci. Rev. 21, 121–126. Gualtieri, L., Glushkova, O., Brigham-Grette, J., 2000. Evidence for restricted ice extent during the last glacial maximum in the Koryak Moutains of Chukotka, far eastern Russia. Geol. Soc. Am. Bull. 112, 1106–1118. Hubberten, H.-W., Andreev, A., Astakhov, V.I., Demidov, I., Dowdeswell, J.A., Henriksen, M., et al., 2004. The periglacial climate and environment in northern Eurasia during the last glaciation. Quatern. Sci. Rev. 23, 1333–1357. Kind, N.V., 1975. Glaciations in the Verkhojansk Mountains and their place in the radiocarbon chronology of the Late Pleistocene Anthropogene. Biul. Perygl. 24, 41–54.
881
Kind, N.V., Kolpakov, V., Sulerzˇicku, L.D., 1971. To the problem of the age of glaciations in the Verkhoyansk area. Proc. USSR Acad. Sci. Geol. Ser. 10, 135–144. (in Russian). Kolpakov, V.V., 1979. Glacial and periglacial relief of the Verkhojansk glacial region and new radiocarbon datings. In: Muzins, A.I. (Ed.), Regional Geomorphology of Newly Developed areas. Geographical Society of the USSR, Moskau, pp. 83–97. Kolpakov, V.V., Belova, A.P., 1980. Radiocarbon dating in the glacial region of Verkhoyan’ye and its framing. In: Ivanova, I.K., Kind, N.V. (Eds.), Geochronology of the Quaternary period. Nauka Press, Moskau, pp. 230–235. Koreisha, M.M., 1991. Glaciation of the Verkhoyansk-Kolyma Region. Academy of Sciences of the USSR, Moskau Soviet Geophysical Committee (in Russian). Lydolph, P.E., 1977. Climates of the Soviet Union. World Survey of Climatology 7. Elsevier, Amsterdam. Mangerud, J., Gosse, J., Matiouchkov, A., Dolvik, T., 2008. Glaciers in the Polar Urals, Russia, were not much larger during the Last Global Glacial Maximum than today. Quatern. Sci. Rev. 27, 1047–1057. Murzin, A.M., 2003. Glaciers of Yakutia. Nauka i technika w Jakutii (Science and techniques in Yakutia) 2 (5), 102–107. (in Russian). Schirrmeister, L., Siegert, C., Kuznetsova, T., Kuzmina, S., Andreev, A., Kienast, F., et al., 2002. Paleoenvironments and paleoclimatic records from permafrost deposits in the Arctic region of Northern Siberia. Quatern. Int. 89, 97–118. Spielhagen, R.F., Erlenkeuser, H., Siegert, C., 2005. History of freshwater runoff across the Laptev Sea (Arctic) during the last deglaciation. Global Planet. Change 48, 187–207. Stauch, G., 2006. Jungquarta¨re Landschaftsentwicklung im Werchojansker Gebirge, Nordost Sibirien (Late Quaternary landscape development in the Verkhoyansk Mountains, North-Eastern Siberia). Aachener Geographische Arbeiten 45, Aachen (in German, English Summary), 1–179. Stauch, G., Gualtieri, L., 2008. Late Quaternary glaciations in North-Eastern Russia. J. Quatern. Sci. 23, 545–558. Stauch, G., Lehmkuhl, F., 2008. Dry climate conditions in Northeast Siberia during the MIS2. In: Kane, D.L., Hinkel, K.M. (Eds.), Proceedings of the Ninth International Conference on Permafrost, University of Alaska Fairbanks June 29–July 3, 2008. University of Fairbanks, Fairbanks,1701–1704. Stauch, G., Lehmkuhl, F., 2010. Quaternary glaciations in the Verkhoyansk Mountains, northeast Siberia. Quatern. Res. 74, 145–155. Stauch, G., Lehmkuhl, F., Frechen, M., 2007. Luminescence chronology from the Verkhoyansk Mountains (North-Eastern Siberia). Quatern. Geochronol. 2, 255–259. Svendsen, J.I., Alexanderson, H., Astakhov, V.I., Demidov, I., Dowdeswell, J.A., Funder, S., et al., 2004. Late Quaternary ice sheet history of northern Eurasia. Quatern. Sci. Rev. 23, 1229–1271. Velichko, A.A., Spasskaya, I., 2002. Climatic change and the development of landscapes. In: Shahgedanova, M. (Ed.), The Physical Geography of Northern Eurasia. Oxford University Press, Oxford, pp. 36–69. Zamoruyev, V., 2004. Quaternary glaciation of north-eastern Asia. In: Ehlers, J., Gibbard, P.L. (Eds.), Quaternary Glaciations—Extent and Chronology, Part III: South America, Asia, Africa, Australasia, Antarctica. Elsevier, Amsterdam, pp. 321–323.
Extent and Timing of Quaternary Glaciations in the Verkhoyansk Mountains Georg Stauch* and Frank Lehmkuhl Department of Geography, RWTH Aachen University, Templergraben 55, 52056 Aachen, Germany *Correspondence and requests for materials should be addressed to Georg Stauch. E-mail: [email protected]
64.1. INTRODUCTION
64.2. VERKHOYANSK MOUNTAINS
The extent and timing of Quaternary glaciations in the Verkhoyansk Mountains have been debated since the beginning of the twentieth century. The remoteness of these vast mountain areas and harsh climate conditions has constrained Quaternary research for many centuries. The location of the mountain system at the eastern edge of the Atlantic-influenced Eurasian continent is a unique situation in which to study not only regional climate effects but also the influence of Quaternary ice sheets in the north of the continent. The Verkhoyansk Mountains stretch for about 1200 km from the Laptev Sea coast to central Yakutia in an s-shaped manner (Fig. 64.1). Maximum elevations of 2959 m a.s.l. are reached in the south-eastern part of the mountains, in an area known as the Suntar Chajata. However, in the northern parts, most summits are around 1400 and 2000–2200 m a.s.l. in the central part. Harsh climate conditions are characteristic of the area and the so-called ‘cold pole’ of the Earth is situated at the village of Oimjakon, which is just 100 km away from the eastern branch of the mountain system. The mean annual temperature is at most stations below 10 C with mean temperatures in January of 40 and up to 20 C in July. Present-day precipitation varies considerably in the area as a consequence of orographic effects. In the valley of the Lena River in the west of the region, climate stations record values of around 200 mm a year, while on the western side of the mountains up to 700 mm are recorded. On the eastern side of the Verkhoyansk Mountains, values drop again to 130 mm (Lydolph, 1977; Murzin, 2003). At present, only two parts of the Verkhoyansk Mountains contain glaciers. In the northern branch, some isolated glaciers with a maximum length of 3.5 km exist (Stauch, 2006). In the high parts of the Suntar Chajata, an area of more than 200 km is currently glaciated (Koreisha, 1991; Ananicheva and Krenke, 2005).
Early reports of past extensive glaciations have been made by several Russian researchers such as V. Obruchev and V.N. Saks in the first half of the twentieth century. However, detailed research on the extent and timing of the Quaternary glaciations began in the 1960s with the work of V.N. Kind, V.V. Kolpakov and A.P. Belova and several other scientists. This work resulted in different models of Quaternary glaciations in the Verkhoyansk Mountains. Most research has been undertaken in the central Verkhoyansk Mountains, especially in the valley of the Tumara River (Fig. 64.1). Small terminal moraines in the main valleys of the central Verkhoyansk Mountains and in the western foreland have been dated by Kind (1975) on the basis of their relative position as remnants of retreating gLGM (global Last Glacial Maximum; ca. 21 cal. ka BP, 18 14 C ka BP) glaciers and Early Holocene advances (Fig. 64.2). Three large terminal moraines in the western foreland have been dated by radiocarbon to 29–15 14C ka BP (Kind, 1975; Kolpakov, 1979; Kolpakov and Belova, 1980). According to Kind (1975), a further terminal moraine, marking an even larger glacial extent, dates to 33–30 14C ka BP. This moraine had been named Karginsk after the Karginsk Interstadial of the Siberian stratigraphy and had not been identified in other area of north-eastern Russia. Two more extensive moraines are only preserved as ground moraine with no terminal ridges at the surface. They have been attributed to the early part of the last glacial cycle and the previous glacial cycle (Kind et al., 1971; Kind, 1975). Several maps have been published in the past few decades regarding the extent of glaciations mainly during the gLGM. According to Grosswald and Hughes (2002), north-eastern Russia was completely covered by a large ice sheet with maximum ice thickness of more than 2000 m east of the Verkhoyansk Mountains. This ice sheet
Developments in Quaternary Science. Vol. 15, doi: 10.1016/B978-0-444-53447-7.00064-7 ISSN: 1571-0866, # 2011 Elsevier B.V. All rights reserved.
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Quaternary Glaciations - Extent and Chronology
FIGURE 64.1 The Verkhoyansk Mountains (the hatched box indicates the central Verkhoyansk Mountains: (A) Tumara River; (B) Djanushka River).
was part of a large pan-Arctic Ice Sheet covering most of the Arctic regions. This hypothesis has been rejected by several studies in recent years (e.g. Velichko and Spasskaya, 2002; Brigham-Grette et al., 2003; Svendsen et al., 2004; Spielhagen et al., 2005). Other reconstructions show mountain glaciations of much smaller extent (e.g. Arkhipov et al., 1986; Zamoruyev, 2004). However, all maps indicated glaciers with a length of more than 100 km on the western side of the Verkhoyansk Mountains stretching from the high mountain areas down to the foothills and out in the forelands. Research from the start of the twenty-first century, based on a re-evaluation of the morphological landforms in combination with IRSL (infrared-stimulated luminescence) dating of overlying aeolian sediments as well as glacial sediments, resulted in a different chronology of glaciations in the Verkhoyansk Mountains. According to these new results, glaciations in the central Verkhoyansk Mountains were either very limited or non-existent during the past 50 ka (Fig. 64.2). The last glaciation which left traceable morphological landforms occurred before 50 ka (Stauch et al., 2007). Terminal moraines (termed I; Fig. 64.3) related to this glaciation have been deposited
inside of the mountain system and are relatively small compared to older glacial landforms. These results correspond with studies from the Charaulach Mountains in the northernmost part of the Verkhoyansk Mountains close to the delta of the Lena River. This mountain chain has not been glaciated at least during the past 60 ka (Schirrmeister et al., 2002; Hubberten et al., 2004). Glacial deposits at the mountain front of the Verkhoyansk Mountains are generally much larger in size. In the Tumara River valley, terminal moraines (II) form impressive arcs with diameters of 20 km. Aeolian sediments covering these terminal moraines have been dated to 19.2 and 46.8 ka (Stauch et al., 2007) but on the basis of their relative position, the underlying glacial sediments were deposited prior to 50 ka. A third set of terminal moraines further downstream of the rivers is even larger. Similar glacial landforms can be observed in many river valleys in the western foreland of the Verkhoyansk Mountains. IRSL ages indicate formation around 80– 90 ka ago. At the Tumara River, one further terminal moraine is preserved (IV), while two more former glacier terminus positions can be reconstructed in the Djanushka River valley (IV and V). Preservation of both moraines is
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Extent and Timing of Quaternary Glaciations in the Verkhoyansh Mountains
879
64.3. REGIONAL COMPARISON
FIGURE 64.2 Extent and timing of glaciations in the central Verkhoyansk Mountains (grey: according to Kind et al., 1971; black: Stauch et al., 2007).
only sketchy as a result of fluvial erosion caused by the younger glacial advances and in the case of the outermost moraine V, the Lena River. According to the IRSL ages obtained from the Tumara River, moraine IV gives an age of 100–120 ka, while the sediments of the outermost moraine at the Djanushka River (V) have been deposited around 135 ka. However, only two IRSL ages are at present available from this moraine V (Stauch et al., 2007). Similar successions of terminal moraines have been mapped in several neighbouring valleys on the western side of the Verkhoyansk Mountains (Stauch, 2006; Stauch and Lehmkuhl, 2010). In contrast, terminal moraines on the eastern side of the mountains are smaller and closer to the higher part of the Verkhoyansk Mountains. Late Quaternary glaciers must have been much smaller on this side and all terminal moraines have been deposited inside the valleys of the mountains and not on the piedmont. These results indicate a primary moisture source from western direction during times of glaciations and, therefore, a similar situation as today. This is also confirmed by the orientation of cirques and cirque floor elevations. Nearly 500 cirques have been mapped in the central Verkhoyansk Mountains on the basis of satellite images. Cirques located at lower elevations are generally found on the western side, while cirques on the eastern side are 500 m higher. The average cirque floor elevation is around 1400 m a.s.l. (Stauch, 2006).
Comparing these results with recent studies from areas west and east of the Verkhoyansk Mountains shows some similar trends in the timing of glaciations but also some striking differences. Moisture-bearing winds from the west have been strongly influenced by development of the large ice sheets in the northern part of the Eurasian continent. Svendsen et al. (2004) reconstructed the extent of the Eurasian Ice Sheet for four time periods in the Late Pleistocene. The two segments of the ice sheet, the Scandinavian Ice Sheet and the Barents–Kara Ice Sheet, developed opposite trends (Svendsen et al., 2004; Chapter 28). While the western sector became progressively larger during this period, the eastern sector became smaller in size. The trend of the Barents–Kara Ice Sheet is therefore comparable to the development of mountain glaciations in the Verkhoyansk Mountains. This is further confirmed by the development of mountain glaciations in the Polar Urals (Fig. 64.4). An age of around 20 ka has been obtained for a terminal moraine only 1 km from the present ice margin, while moraines further away from the mountains have an age of 50–60 ka (Mangerud et al., 2008). A similar age has been given by Astakhov and Mangerud (2007) for river terraces related to glaciers from the Putorana Plateau. East of the Verkhoyansk Mountains, only few results concerning the extent and timing of Quaternary glaciations in the Russian Far East are available (Chapter 63). A recent summary highlighted two areas of more detailed studies, the Pekulney Mountains in the Anadyr Uplands and the Koryak Mountains (Fig. 64.4) on the eastern side of the Eurasian continent (Stauch and Gualtieri, 2008). Three suites of terminal moraines have been mapped and dated in the Pekulney Mountains (Brigham-Grette et al., 2003). The youngest of these sets has been termed the Kuveveem Moraines. Cosmogenic isotope dating revealed a formation during marine isotope stage (MIS) 2. Remnants of two older glaciations have been identified at the Tanyurer River. The upper moraine has been termed the Chumyveem moraine. Cosmogenic isotope dating of erratic boulders has yielded ages between 41 and nearly 70 ka. The second moraine (Anadyr River moraine) has been dated on the basis of morphological criteria. Brigham-Grette et al. (2003) assumed Middle to Early Pleistocene age for this moraine. In the Koryak Mountains, a study by Gualtieri et al. (2000) presented evidence for at least two Pleistocene glaciations. A younger glaciation occurred again during MIS 2, while cosmogenic isotope data from the lower Anadyr depression, north of the mountains, indicate a glaciation before 50 ka. No terrestrial evidence has yet been found relating to the early part of the last glacial cycle (Weichselian Stage). However, BrighamGrette (2001) and Brigham-Grette et al. (2001) suggested, on the basis of glaciomarine sediments, a rapid glaciation of Chukotka Peninsula directly after the last interglacial.
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Quaternary Glaciations - Extent and Chronology
I I
II II III III IV IV V
FIGURE 64.3 Terminal moraines in the Tumara and Djanushka valley (modified from Stauch et al., 2007).
FIGURE 64.4 Northern Asia and selected mountain areas.
64.4. CONCLUSION Quaternary glaciation in the central Verkhoyansk Mountains became more limited in extent throughout the Late Quaternary. The largest extent of ice has so far been attributed to the penultimate glacial cycle (Saalian Stage) prior to the Eemian interglacial. Further glaciations occurred at around 100–120, 80–90 and before 50 ka. It seems that there was no glaciation in the area during the gLGM
(MIS 2). However, whether the dated terminal moraines during the early part of the glacial cycle represent individual glaciations with a considerable ice retreat between, or whether they are remnants of glacier oscillations, remains one of the unanswered questions. The extent and timing of glaciations in the Verkhoyansk Mountains shows similar trends to mountain glaciations further west and the Barents– Kara Ice Sheet (Chapters 27 and 28). However, there have been more glaciations identified in the Verkhoyansk area
Chapter 64
Extent and Timing of Quaternary Glaciations in the Verkhoyansh Mountains
during the early part of the last glacial cycle. East of the Verkhoyansk Mountains, a different pattern is recognisable. In these areas, glaciation also decreased in size progressively through the last glacial cycle, but prominent terminal moraines were developed during MIS 2. The asynchronous formation of glaciers on the western and eastern slopes of the Verkhoyansk Mountains is the result of different moisture sources. In the west of the Eurasian continent, the growth of the Scandinavian Ice Sheet blocked the moisture-bearing air masses from entering the far east of Siberia and prevented the growth of glaciers in the Verkhoyansk Mountains during the MIS 2, despite very low temperatures. In contrast, on the easternmost side of the continent, moisture from the Pacific supported the development of glaciers in the Pekulney and Anadyr Mountains during MIS 2 (Stauch and Gualtieri, 2008; Stauch and Lehmkuhl, 2008). However, there are still large areas in north-eastern Russia with large mountain systems where no dating results for glacial sediments are available. Further research in this interesting area is still needed.
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