Correlation and Interpretation of Paleosols and Loess Across European Russia and Asia Over the Last Interglacial–Glacial Cycle

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Quaternary Research 60 (2003) 101–109 www.elsevier.com/locate/yqres

Correlation and interpretation of paleosols and loess across European Russia and Asia over the last interglacial–glacial cycle

Nathaniel W. Rutter,a,* Dean Rokosh,a Michael E. Evans,b Edward C. Little,c Jiri Chlachula,d and Andrei Velichkoe

a Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E3 b Institute for Geophysical Research, University of Alberta, Edmonton, Alberta, Canada T6E 2G1 c Canada-Nunavut Geoscience Ofﬁce, Box 2319, Iqaluit, Nunavut, Canada X0A 0H0 d University of Zlin, Palaeoecology Laboratory, Zlin 76272, Czech Republic e Institute of Geography RAS, Laboratory of Evolutionary Geography, Staromonetny Lane 29, Moscow 109017, Russia

Received 4 November 2002

Abstract Loess-paleosol sequences of the last interglacial-glacial cycle are correlated from European Russia to central Siberia and the Chinese Loess Plateau. During cold periods represented by marine oxygen isotope stages (OIS) 2 and 4, loess deposition dominated in the Russian Plain and the Loess Plateau. In central Siberia, loess deposition took place also, but five to seven thin, weakly developed paleosols are identified in both stages. OIS 3, in the Chinese Loess Plateau near Yangchang, consists of a loess bed that is flanked by two weakly developed paleosols. At Kurtak, Siberia, OIS 3 is represented by two distinct, stacked paleosols with no loess bed separating the paleosols. In the Russian Plain, OIS 3 consists of a single, possibly welded paleosol, representing upper and lower stage-3 climates. Brunisols and Chernozems dominate the profiles in China and Siberia, whereas Regosols, Luvisols, and Chernozems are evident in the northern and southern Russian Plain, respectively. OIS 5 is represented in China and the Russian Plain by pedo complexes in a series of welded soils, whereas in contrast, the Kurtak site consists of six paleosols with interbedded loess. The paleosols consist largely of Brunisols and Chernozems. Although the three areas examined have different climates, geographical settings, and loess source areas, they all had similar climate changes during the last interglacial-glacial cycle. © 2003 University of Washington. Published by Elsevier Inc. All rights reserved.

Keywords: Paleoclimate; Loess; Paleosol; Last glacial maximum; Quaternary; Russian Plain; Siberia; Isotope stage; Chinese loess plateau; Stratigraphy

Introduction took his loess investigations to China. This contribution is a continuation of his legacy. In the early sixties, Troy Pe´we´ was the senior author’s In the past 12 years, we have investigated Quaternary Masters program supervisor at the University of Alaska. loess-paleosol sequences in China, Siberia, and the Russian Although my thesis concerned the flow of Gulkana Glacier, Plain as part of Canada’s project on Climate System History Troy’s broadly based, eclectic view of the Quaternary en- and Dynamics. The objective here is to correlate and exam- sured that his students would take a holistic view of the ine high-resolution loess-paleosol sequences at three loca- period when solving scientific problems. His constant ques- tions covering more than 60° of longitude (Fig. 1). Each tion to us was “Do you understand the big picture?” The area has different geographical settings and modern climate, field trips around Fairbanks instilled in me an appreciation and all are key areas for studying loess deposition and of the importance of loess in Quaternary studies. Later, Troy paleosols. The sediments at all three sites span a similar time interval and are: (1) three sections at Likhvin, Go- * Corresponding author. lolobovo, and Korostylievo in the Russian Plain (Lat. 56°N, E-mail address: [email protected] (N.W. Rutter). Long. 36°E; 55°N, 38°E; and 52°N, 42°E, respectively); (2)

0033-5894/03/$ – see front matter © 2003 University of Washington. Published by Elsevier Inc. All rights reserved. doi:10.1016/S0033-5894(03)00069-3 102 N.W. Rutter et al. / Quaternary Research 60 (2003) 101–109

Fig. 1. Index map of the sites discussed in the text. The map is a modified version downloaded from the University of Texas at Austin, Perry Castaneda Library at http://www.lib.utexas.edu/maps/asia.html. a 35-m section at Kurtak in south-central Siberia, Russia tions of 150 and 170 m asl, respectively, in the Russian (54°N, 92°E); and (3) two sections at Yangchang and Yulin Plain. Both the Likhvin and Gololobovo sites lie along the in the central Loess Plateau, China (37°N, 110°E; and 38°N, north flank of the Oka River. The Korostylievo site is 110°E, respectively). located on the south bank of the Vorona River at about 100 m asl, approximately 435 km southeast of the Go- lolobovo (Velichko et al., 1997; Little, 2002). Physiographic setting The 35-m section at Kurtak (Fig. 1), near the geographic center of Asia, lies at an elevation of about 250 m asl. Likhvin and Gololobovo (Fig. 1) are located about 125 Kurtak is located on the north flank of the Yenisey River km southwest and 125 km southeast of Moscow at eleva- within the Northern Minusinsk Basin. The Altay-Sayan N.W. Rutter et al. / Quaternary Research 60 (2003) 101–109 103

Mountains to the west, along with the Eastern Sayan Moun- are about Ϫ11° and 18°C, respectively (NOAA, 1991). At tains and the Tannu Ola Range to the east and south, Volograd (350 km southeast of Korostylievo) mean annual respectively, orographically isolate the Kurtak area from precipitation is about 310 mm and is highest during the southerly climatic influences (Chlachula, 1995). winter months. January and July average temperatures are Yanchang and Yulin (Fig. 1) are located in the central about Ϫ12° and 24°C, respectively. Korostylievo is about Loess Plateau of China, each at an elevation of about half the distance between Moscow to Volograd. Mean an- 1200 m asl. The Tibetan Plateau and the east-west trending nual precipitation at Krasnoyarsk, about 100 km northeast Qinling Mountains are about 350 km south of Yanchang of Kurtak, is about 490 mm, with most of the precipitation and largely block the transport of dust further southward occurring during the summer months. Average January and (Liu, 1985). The deserts of China are located to the north July temperature are about Ϫ17° and 18°C, respectively and west of the Loess Plateau (Liu, 1985). (NOAA, 1991). Kurtak is located in an active permafrost area. At Yanchang, mean annual precipitation and temperature are about 550 mm and about 8°C, and Yulin’s about Loess sources 400–450 mm and about 7° to 8°C with precipitation occurring principally during July to September of the summer The paleogeography of the three areas presents an interest- monsoon season (Zhao, 1986). ing contrast in glacial landscape and dust sources during the last glacial period (marine oxygen isotope stages [OIS] 2, 3, and 4). The Likhvin, Gololobovo, and Korostylievo sites are Methods located in the Russian Plain near numerous river valleys and were about 250 to 500 km south of the southern limit of the Grain-size analyses from the Russian and Siberian sites Fennoscandian Ice Sheet during the last glacial maximum were performed at the University of Alberta on a Micro- (Velichko et al., 1997; Little, 2002). Kurtak is situated within meritics Sedigraph 5100 after removal of organic material a mountain range, where there is evidence for the presence of and carbonate. At present, grain-size analyses at Kurtak alpine glaciers during the last glaciation, although none have been restricted to about every 20–30 cm and every 30 reached the Kurtak area. There is no evidence of glaciers in the cmto1mintheRussian Plain sites. Aliquots of sampled Loess Plateau or the northern deserts of China. material for magnetic susceptibility analyses were loosely Loess on the Russian Plain forms a blanket that covers an packed into 8-cc plastic boxes and measured on a Barting- area of over one million square kilometers. It is derived ton MS2 meter at the University of Alberta. At Yanchang from the northern alluvial and lacustrine plains that formed and Yulin, samples were taken every 5–10 cm. Grain-size in front of the advancing and retreating Pleistocene ice and susceptibility analyses were performed in China at the sheets (Velichko, 1990). At Kurtak, loess is located along Academy of Sciences, Beijing. Susceptibility was deter- the terraces of the Yenisey River and is derived from the mined in the lab on an ϳ50-g bagged sample, using a upper Yenisey valley, and from local bedrock (Chlachula et Bartington MS2 susceptibility meter. Grain-size analysis al., 1997). Loess in China comes largely from the northern was performed on a PRO-700 SK Laser Micron Sizer after deserts (Liu, 1985), and to a lesser degree from cold, south- removal of organic material, carbonate, and pedogenic iron. erly winds emanating from the Tibetan Plateau (Fang et al., The paleosols were identified by field characteristics and 1999) as well as from the upper-level Westerlies (Zhang et micromorphology. Some additional analyses (names, com- al., 1996). position, geochemistry) were prepared at the Institute of Geography, Russian Academy of Sciences. The soils were classified according to the Canadian Sys- Modern climate tem of Soil Classification (Soil Classification Working Group, 1998). In general, the Canadian System corresponds According to the Koppen-Geiger climate classification more closely to systems used in Europe and Asia than with system (Geiger and Pohl, 1954), Likhvin, Gololobovo, and other classifications. The paleosols were identified by field Korostylievo are classified as Dfb climates (humid conti- characterisation and micromorphology. nental with severe winter, no dry season, warm summer). Kurtak has a Dwc climate (subarctic, continental, dry winter, cool summer) and Yanchang and Yulin are classified as Chronostratigraphy a BSk climate (mid-latitude, cold semiarid steppe). Precip- itation and temperature data for the European Russia and Chronostratigraphy at the three sites is determined by a Siberian sites are derived from major cities near the sites combination of 14C dates, optically stimulated luminescence (NOAA, 1991). Mean annual precipitation at Moscow is (OSL), thermoluminescence (TL), paleontological data, and about 630 mm (125 km north of Lihkvin and Gololobovo), correlation to other nearby well-dated sites. Little et al. (in with precipitation slightly higher during summer months press) have applied the OSL dating method to the Likhvin, than winter months. Average January and July temperature Gololobovo, and Korostylievo sites in the Russian Plain 104 N.W. Rutter et al. / Quaternary Research 60 (2003) 101–109

Fig. 2. Lithostratigraphic and pedostratigraphic logs of the Russian Plain sites. Likhvin and Korostylievo diagrams represent the larger, upper portions of sedimentary successions whereas the Gololobovo section diagram is derived from three smaller composite sections. Except where noted, ages were obtained from optical dating techniques [cf. Little et al. (in press); Little (2002)]. The “⌽ units” are used to characterize lithologic units and represent average grain-size variations based on textural analyses.

(Fig. 2). At Kurtak a single date of 30,400 Ϯ 700 14Cyr thick (Fig. 2). The upper 2 m consists of the present-day B.P. was determined on wood from a paleosol located at Brunisol over colluviated loess exhibiting discontinuous about 10 m depth (Fig. 3). This paleosol is well correlated banding and rare, granule-sized clasts. A 6-cm localized throughout the area to other dated sections that exhibit 14C layer of charcoal fragments, together with oxidized granitic dates of about 30,000–35,000 yr B.P. (Chlachula, 1995; clasts from 2.10 to 2.16 cm, suggests the presence of a fire pit. Chlachula et al., 1997). The paleosols from 16 to 21 m at The charcoal has been dated 14C at about 2700 14C yr B.P. Kurtak were assigned to the last interglacial based on cor- A weakly developed cumulic Regosol underlies colluvi- respondence with regional rodent and mammoth taxa, the ated loess within OIS 2 (Little et al., in press). Below this presence of Paleolithic (Mousterian) stone tools, along with soil is a loess bed (Desna loess horizon; Velichko, 1990) stratigraphic position, and the advanced degree of soil de- which has a basal OSL date of 29,000 yr B.P. (Little et al., velopment (Chlachula et al., 1997). Chlachula (1995) and in press) indicating deposition during the last glacial max- Chlachula et al. (1997) correlated the Kurtak pedo complex imum (OIS 2). Underlying this loess is a cumulic Regosol to the Sukholozhskiy pedo complex (Drozdov et al., 1991) (Bryansk paleosol; Velichko, 1990) that testifies to dust and the Kamenolozhskaya paleosol, both of which were deposition contemporaneous with formation of the soil. 14C assigned to OIS 5. The section at Yanchang has previously dates of this soil obtained from various profiles give an age been correlated to Yulin (Fig. 4) (Sun et al., 1998; Ding et range between 24,000 and 32,000 14C yr (Chichagova and al., 1999) and Weinan (Liu et al., 1995), where the last interglacial-glacial cycle is chronologically well-con- Cherkinsky, 1988; Velichko, 1990). We suggest that the strained by 14C and thermoluminescence dating. Bryansk paleosol corresponds to the warm periods of OIS 3. The ice-wedge pseudomorphs belonging to the Vladimir cryogenic horizon (Velichko and Nechaev, 1984; Morozova Sections in the Russian Plain and Nechaev, 1997) deformed this paleosol and reflect the beginning of the subsequent cold periods of OIS 2. A (a) Likhvin relatively thin (1.5–1.8 m) loess bed (Khotylevo loess horizon; Velichko, 1990) on which the Bryansk paleosol de- The Lihkvin section has a long history of investigations veloped corresponds to OIS 4, dated with an OSL date of (Sudakova, 1993; Bolikhovskaya, 1995). It is about 8.25 m 70,000 Ϯ 7000 yr B.P. N.W. Rutter et al. / Quaternary Research 60 (2003) 101–109 105

modern soil is a bed of loess with a basal OSL date of ϳ28,000 yr B.P. representing OIS 2. In some places the lower part of this bed contains the weakly stratified silty clay. In other places this loess-like sediment is more homo- geneous. The stratified layer is not observed at the other two Russia Plain sites, so a localized pond or lake is postulated. Beneath this bed, correlated with the Desna loess horizon, is a paleosol with gradational contacts from about 3.2 to 3.7 m. Based on micromorphology, field observations, and laboratory data the paleosol is interpreted as a cumulic Regosol forming in a steppe to forest-steppe environment. This paleosol may correspond to late warm period of OIS 3 and therefore the Bryansk paleosol. It formed on a 1.2-m-thick loess bed. An OSL date of about 34,000 yr B.P. was obtained near the middle part of this loess bed. Underlying the loess bed is a single paleosol that corresponds to the Mezin pedo complex, i.e., OIS 5. It consists of Ahe and Bt hori- zons, suggesting this soil belongs to the Luvisolic Order and formed under moist forested conditions. Unlike the Lihkvin and Korstylievo sections, only a single last interglacial paleosol is observed at Gololobovo. The basal sediments at this site are interpreted as, from top to bottom, loess, colluviated loess, and loess-like sediments (so called “blue loess”) that accumulated in ponds, corresponding to the last part of Middle Pleistocene (Little, 2002; Velichko et al., 2000). Two OSL dates of 117,000 Ϯ 21,000 and 122,000 Ϯ 15,000 yr B.P. were obtained 1 m below the Mezin soil complex.

(c) Korostylievo Fig. 3. Magnetic susceptibility, grain-size variations, and stratigraphic profile at Kurtak, Siberia. The dashed line represents the grain-size data The modern soil at Korostylievo is an orthic brown and the solid line the magnetic susceptibility. CH, Chernozem; BR, Brunisol; GR, Gleyed Regosol; CL, Colluviated loess; L, Loess. Chernozem that formed within the modern forest-steppe environment (Fig. 2). The soil overlies a 1-m-thick loess bed that correlates to the last glacial period OIS 2. The Below the loess of OIS 4 is the Mezin pedo complex, underlying loess-paleosol unit corresponds to OIS 4 and 3, corresponding to the different substages of OIS 5. This pedo respectively. An OSL date of ϳ57,000 yr B.P. was deter- complex includes two phases of soil formation. The upper mined from loess just below the paleosol. The loess exhibits phase consists of a paleosol with a dark humus horizon an increase in blocky structure upward culminating in the (Ah-B) corresponding to substage OIS 5a and perhaps sub- formation of an eluviated brown Chernozem that corre- stage OIS 5b, formed during the Krutitsa interstade (Veli- sponds to the warm period(s) of OIS 3. During the last chko, 1990). According to T.D. Morozova (personal com- interglacial period, OIS 5, two relatively well-developed munication, 2002), this chernozem-like paleosol could form Chernozemic soils are observed with the lower soil being in a cold steppe environment. The lower of the two pa- better developed based on field, laboratory, and micromor- leosols exhibits a profile Ae-Bt1-Bt2 identified as a Luvisol, phological analyses. We classify the lower paleosol as a suggesting strong pedogenic influence under forested con- dark-brown Chernozem and the upper OIS-5 paleosol as a ditions (Morozova, 1981). The lowermost unit is interpreted brown Chernozem. The three paleosols of OIS 5 and 3 show as a glacial lacustrine environment contemporaneous with a progressive weakening in soil development up-section deglaciation of the region (Sudakova, 1993; Little et al., in suggesting that higher temperatures and moisture occurred press). Cryoturbation has deformed the fine silt and clay early during OIS 5 with progressively weaker soil forming laminae of this unit. conditions occurring during late OIS 5 and 3. Loess accumulation rates were greatly reduced during OIS 5 (Little, (b) Gololobovo 2002). The data suggest that significant pedogenic over- printing of OIS-5 soils that developed in OIS 6 may have The surface soil at Gololobovo is a Luvisol residing in a occurred. This is in striking contrast to the cumulic soils of forest to forest-steppe environment (Fig. 2). Underlying the the last interglacial period in China and Siberia where loess 106 N.W. Rutter et al. / Quaternary Research 60 (2003) 101–109

Fig. 4. Correlation between the Yulin and Yanchang sections. Yulin TL dates are from Sun et al. (1995), while the isotope stage dates are from the age model of Liu et al. (1995, 1998).

deposition continues during warm periods. This overprint- brown Chernozem. More than ﬁfteen 14C dates have been ing is yet unexplained. derived from the paleosol ranging from 24,000 to 33,000 14C yr B.P. (Chichagova and Cherkinsky, 1988; Velichko, 1990; Velichko et al., 1997). Below this soil is a loess bed Correlation of the Russian Plain Sediments corresponding to OIS 4, although the presence of OIS 4 at Gololobovo is not conﬁrmed. The top of OIS 4 according to The Russian Plain covers a large area, so these sites offer Martinson et al. (1987) is about 59,000 yr and may be as only a glimpse of the complexity of the Russian Plain young as 50,000 yr according to Liu et al. (1995, 1998). The geology during the last interglacial-glacial cycle (Velichko two OSL dates Ͼ117,000 and 122,000 yr B.P. provide a et al., 1997). The OIS-2 loess, below the modern soil (Fig. lower limit for the age of the bed and could correspond to 2), is continuous throughout the area and is thickest at the loess deposited during the late Middle Pleistocene. western Lihkvin site. The ponding at Gololobovo attests to, During the last interglacial period, two soils are observed perhaps, the presence of brief weak warm periods during the at both Lihkvin and Korostylievo. In both cases, the lower last glacial cycle, although a regional pattern of lake sedi- soil is better developed. At Korostylievo, the soils are Cher- mentation during this time is not presently observed. The nozemic and formed in a steppe environment, whereas the Bryansk soils corresponding to OIS 3 appear to have devel- soil development at Lihkvin is related to forested conditions oped in a cold steppe environment and exhibit weaker or perhaps a forest-steppe environment. The OSL dates at development than the modern and last interglacial soils in Gololobovo suggest that the soil formed during the late, last all three locations. The OIS 3 soil is best developed in the interglacial period and, similar to the nearby Lihkvin site, southern-most site of Korostylievo, where it is an eluviated was developed under forested conditions. N.W. Rutter et al. / Quaternary Research 60 (2003) 101–109 107

Sections at Kurtak, Siberia than the welded pedo complex viewed at Yanchang and in the southern Loess Plateau. A striking feature of the Kurtak pedostratigraphy is the relatively weak Brunisolic and Regosolic soils that are present in the upper portion of OIS 4 and the lower portion Correlation of the Russian Plain, Siberian, and of OIS 2 (Fig. 3). There are no less than seven soils ob- Chinese loess-paleosol records served in OIS 4, and 5 soils in OIS 2. The paleosol representing OIS 3 is actually two soils, Figure 5 shows our correlation of the sites in the Russian with a Brunisol overlying a parkland Chernozem of similar Plain, Siberia, and China. For convenience, only the Lih- thickness and exhibiting intensive cryoturbation (the latter kvin site from the Russia data and Yanchang from the Loess paleosol yielded the 14C date). The lower soil is better Plateau are used for this comparison. Loess deposited dur- developed than the upper soil (Chalchula et al., 1997). The ing OIS 2 is present in all areas, with the thickest deposits upper soil may have developed through the silty parent in China and Siberia. At Kurtak and Yanchang, winter material and welded to the lower Chernozem during a pe- temperatures are dominated by the Siberian High Pressure riod of low dust input and climatic amelioration. cell located near Lake Baikal, Russia. This cell may have At Kurtak, the best-developed soil during the last inter- strengthened during cold episodes of the last glacial period glacial period is a Chernozem, located at a depth of about (Ding et al., 1995). The Russian Plain sites were influenced 20 m (Fig. 3). Underlying this soil is a bed of loess and a by proximity to the Fenno-Scandian Ice Sheet. Cryoturba- Brunisol, with the paleosol perhaps marking the onset of the tion or ice wedges occur in all three sites. The weak soils of last interglacial period. Chalchula (1995) and Chalchula et OIS 2 and 4 are the most observable difference between the al. (1997) show that Brunisols in the Kurtak area are asso- three areas. The soils represent a brief change to a warmer ciated with a parkland-forest environment. The Chernozem and wetter climate that is reminiscent of the interstades of represents a change to a more continental climate with an the last glacial period seen in Greenland ice cores (Grootes increase in summer temperature similar to the present-day et al., 1993). There is evidence of similar interstades in the climate and soils. Chinese records, but these warm periods are not readily identified in the field. High-resolution climate proxy vari- ables such as magnetic susceptibility and grain size are needed to delineate these brief warm periods in the Loess Sections in the Chinese Loess Plateau Plateau. The presence of these soils at Kurtak may suggest that this area, dominantly a subarctic continental regime, is In the Loess Plateau, soil development increases south- exceptionally sensitive to brief changes in climate. Further- ward in response to a warmer and wetter climate. In con- more, for these soils to develop there must be a reduction in trast, at Yulin no soils are evident during the last glacial dust input relative to the rate of soil development. Evi- period (Fig. 4). Here, an increase in the loess accumulation dently, loess accumulation rates in China were still high, rate, near the cooler and drier desert, occurred at the ex- relative to soil development during these short warm peri- pense of soil development. The result is time-equivalent ods. In the Russian Plain, the sections are perhaps too thin, loess sedimentation equal to two OIS-3 soils present at relative to the sample interval, to identify millennial-scale Yangchang (Rokosh et al., in press). At Yanchang, the last warm periods. In this respect, the presence of lake sedi- interglacial soils are the best developed, relative to the ments during the glacial period at Gololobovo may hold modern soil, followed by the lower and upper OIS-3 soils, promise for identifying short warm periods in the Russian respectively. The latter two soils developed during intersta- records. des of the last glacial period, where a slight increase in In all three areas, excluding Gololobovo, the last inter- insolation in the upper atmosphere is evident relative to the glacial soil is a pedo complex consisting of at least two intervening cold periods (Berger and Loutre, 1991). Typi- soils. Grassland soils dominate the profiles in China, Kur- cally, the chernozem-like soils are associated with a steppe tak, and Korostylievo, while perhaps a moister and more environment (Liu, 1985; Rutter and Ding, 1993). maritime climate near Moscow resulted in the development The last interglacial period in the Loess Plateau is rep- of forest soils at Lihkvin and Gololobovo. The Kurtak resented by a welded pedo complex that exhibits no less profile exhibits no less than five warm periods during the than three soil-forming periods that have been correlated to last interglaciation, rather than the classic three warm peri- OIS 5a, c, and e. The lowest paleosol is generally the best ods denoted by OIS 5a, c, and e. This is also seen at Yulin, developed soil, as at Yanchang, although this is not always where the magnetic susceptibility shows at least five peaks observed (Sun et al., 1995). Clay cutans are seen in soils of in the record reflecting multiple warm periods. The basal the southern Loess Plateau (Rutter et al., 1991), providing soil during the last interglacial at Kurtak is a Brunisol evidence for a forest cover flanking the Qinling Mountains. according to our present analysis. Further chronostrati- Closer to the desert source at Yulin the complex consists of graphic refinement of the OIS 6/5 transition is needed to a series of loess and paleosol strata, similar to Kurtak, rather determine if the Brunisol marks the onset of the last inter- 108 N.W. Rutter et al. / Quaternary Research 60 (2003) 101–109

Fig. 5. Pedostratigraphic correlation from the Russian Plain to Siberia to China. The dashed line indicates that the correlation of the soil of the Kurtak section is uncertain. The magnetic susceptibility scale at Kurtak is the reverse of the other sections presented in this paper.

glacial period, or if the soil identiﬁes the transition as a grassland environment dominated central Siberia, China, marked by climatic variability, similar to the OIS 2/1 tran- and the southern Russian Plain due to the proliferation of sition. Either way, the trend to climatic amelioration during Chernozemic-type soils. Forest-type soils are viewed in the the stage 6/5 transition, culminating in the warm climate southern Loess Plateau, ﬂanking the Qinling Mountains, maximum of isotope stage 5e, was marked by distinct vari- and in our northern Russian Plain sites during this period. ations in climate in central Siberia. The record at Kurtak clearly shows that there were more than three warm stages during the last interglacial period and that the OIS 6/5 transition is likely marked by climatic Conclusion variability similar to the OIS 2/1 transition.

The three areas that we have examined are quite different in geographic setting, loess source, and modern Acknowledgments climate, yet the records of climatic change during the last interglacial-glacial cycle are similar. The loess-paleosol strata in all the records reflect the changing climate of the This work was carried out as part of Canada’s climate last glacial period, albeit at different resolutions. The change program—Climate Systems History and Dynam- Chinese records show OIS 3 to comprise both loess beds ics—funded by Natural Sciences and Engineering Research and paleosols, reflecting multiple warm and cold periods. Council, Canada, and Environment Canada. The authors In the Siberian and Russian records, OIS 3 shows up as thank these agencies for their generous support. In addition, a stacked or welded paleosol that does not have the the Chinese Academy of Sciences, the Russian Academy of climatic resolution of the Chinese data. OIS 2 and 4 in Sciences, and the University of Ziln supported our project Kurtak are significant because they clearly identify a by providing logistical support, laboratory analyses, and series of thin and weakly developed paleosols that are not scientific advice. N. Catto (Department of Geography, Me- viewed, to the authors’ knowledge, in any other loess- morial University, St. John’s, Newfoundland and Labrador), paleosol records in the world. These soils hold promise J.D. Morosova, V.P. Nechaev, V.V. Semenov, and K.G. for determining the global extent of millennial-scale Dlussky (Geographical Institute, Russian Academy of Sci- warm periods of the last glacial period. ences) are acknowledged for their aid in the description of The paleosols of the last interglacial period suggest that many of the Russian sections. N.W. Rutter et al. / Quaternary Research 60 (2003) 101–109 109

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