Fluvial chronology in the East European Plain over the last 20 ka and its palaeohydrological implications

CATENA-02280; No of Pages 16 Catena xxx (2014) xxx–xxx

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Fluvial chronology in the East European Plain over the last 20 ka and its palaeohydrological implications Andrei Panin ⁎, Ekaterina Matlakhova Lomonosov Moscow State University, Faculty of Geography, Lengory 1, Moscow, 119991, Russia

a r t i c l e

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Article history: Received 13 March 2014 Received in revised form 16 August 2014 Accepted 22 August 2014 Available online xxxx Keywords: Hydroclimate Extreme floods Floodplain occupation by humans Buried alluvial soils Probability densities of radiocarbon and luminescence dates Caspian Sea level change

a b s t r a c t A database containing 983 absolute ages of fluvial deposits was interpreted in palaeohydrological terms and 646 dates were found associated with 754 local palaeofluvial events – geomorphic or sedimentological traces of changing fluvial activity. Combined probability density functions of high- and low-activity dates were used to detect time intervals of different palaeohydrological status. After low fluvial activity during LGM, two palaeohydrological epochs were designated: extremely high activity in the end of MIS 2 (ca. 18–11.7 ka before CE 2000–b2k), and much lower activity in the Holocene. Within the Holocene, two hierarchical levels of hydroclimatic variability were designated according to their duration and magnitude – regional palaeohydrological phases (centuries to few millennia) and regional palaeofluvial episodes (decades to few centuries). Tendency is rather clear of activity lowering in the first half and rise in the second half of the Holocene. Extremes within the palaeohydrological phases were designated as 19 palaeofluvial episodes: 7 high activity HA-episodes, 8 low activity (stability) LA-episodes and 4 contrast, or complex, CA-episodes. In most cases changes of fluvial activity were most likely induced by changing amounts of spring snowmelt runoff. Most distinct correlation of temperature and hydrological regimes was found in the Late Holocene: high fluvial activity corresponded to cold climatic phases (Little Ice Age), low activity, to warm phases (Medieval Climatic Optimum, current climate warming). The suggested fluvial chronology was compared with independent hydroclimatic archives such as palaeosoils and lake levels. Correlation with soil formation/alluviation epochs was found very close, with some exceptions in the Early Holocene. Correspondence of fluvial activity to the Caspian Sea level changes is rather high in the second part of the Holocene and is poor before 4–5 ka b2k, which can be explained by insufficient data behind both types of reconstructions. Correlation of changes in fluvial activity within a west– east transect over Europe revealed relatively poor correlation in the Early and Mid Holocene and much higher synchronism since 3.0 ka b2k, which may indicate increasing role of westerlies in controlling European climates in the Late Holocene. Throughout the whole Holocene, changes of fluvial activity over EEP were governed by natural climate forcing until the last few centuries when land use changes induced accelerated hillslope and gully erosion. © 2014 Elsevier B.V. All rights reserved.

1. Introduction The use of statistical processing of bulked radiocarbon dates to analyze palaeoenvironmental and archaeological chronologies has been increasing considerably since its start in early 1970s in coincidence with the exponential rise of yearly amount and total storage of absolute age determinations (see overviews in Michczynska and Pazdur, 2004; Williams, 2012). Application of this approach for uncovering of the Holocene palaeohydrological and fluvial activity extremes, since having been proposed in early 1990s (Macklin and Lewin, 1993), has been employed in a number of regions in western and central Europe (Hoffmann et al., 2008; Macklin and Lewin, 2003; Starkel et al., 2006; Thorndycraft and Benito, 2006) and Mediterranean north-west Africa ⁎ Corresponding author. E-mail address: [email protected] (A. Panin).

(Zielhofer and Faust, 2008; Zielhofer et al., 2008). Construction of time-dependant age distributions evolved in its statistical techniques from histograms of uncalibrated radiocarbon dates (Macklin and Lewin, 1993) to cumulative frequency plots (Macklin and Lewin, 2003) and finally to probability density functions (PDFs) summed over the arrays of classified dates (Johnstone et al., 2006). Along with radiocarbon chronologies, large arrays of OSL dates were used to establish chronology of slopewash processes (Lang, 2003). General complaints against using cumulative probability functions as a tool for constructing fluvial chronologies stated recently by Chiverrell et al. (2011) were responded to by Macklin et al. (2011). Additional statistical significance tests for reliable interpretation of summed PDFs were proposed by Macklin et al. (2012). Due to the very strict filtering of available radiocarbon dates to select those carrying palaeohydrological signals, the analyzed arrays were relatively small, typically several hundred dates against thousands dates

http://dx.doi.org/10.1016/j.catena.2014.08.016 0341-8162/© 2014 Elsevier B.V. All rights reserved.

Please cite this article as: Panin, A., Matlakhova, E., Fluvial chronology in the East European Plain over the last 20 ka and its palaeohydrological implications, Catena (2014), http://dx.doi.org/10.1016/j.catena.2014.08.016

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used in archaeology (cf. to over 25,000 dates used by Peros et al. (2010) to quantitatively analyze the Paleo-Indian chronologies in North America). However, this statistical approach provided distinct advance in establishing major flood episodes in a variety of European regions and in studying fluvial responses to changes in land use and climate (Hoffmann et al., 2008; Johnstone et al., 2006; Macklin et al., 2005; Starkel et al., 2006) as well as in correlation of palaeohydrological chronologies over Europe (Macklin et al., 2006). In the East European Plain (EEP), the easternmost part of Europe, which constitutes some 40% of its area, several synthesizing studies of fluvial chronology have been completed in the last decade. Epochs of high fluvial activity, or alluviation, and epochs of fluvial stabilization in the central EEP were distinguished in the Holocene from collections of radiocarbon dates mainly from buried soils on river floodplains (Alexandrovskiy and Alexandrovskaya, 2005; Alexandrovskiy and Krenke, 2004; Sycheva, 2006, 2011). Cumulative PDFs were used to establish chronologies for the Holocene gully erosion in the southwestern Moscow Region (Panin et al., 2009) and for fluvial development of the Upper Dnieper River and its tributaries (Panin et al., 2014). Nevertheless, these studies utilize only a small part of the total amount of numerical ages obtained from fluvial deposits over the whole EEP in the last decades. Much of these data are dispersed over a large amount of publications many of them being difficult of access for scientific community. This study is an attempt to collect available fluvial ages from EEP and process them to construct fluvial chronology. We compiled published radiocarbon and luminescence (presumably optical) ages from fluvial deposits into a database, classified dates on palaeohydrological basis and calculated summed PDFs for different classes. Peaks and troughs on PD plots provided detection of short-term fluvial episodes and longer millennium-scale phases of high and low fluvial activity. Age range of dates presented in the database extends through the whole Late Quaternary. Given the rather poor contribution from ages older than LGM, we limit the current study to the last 20 ka. 2. Regional settings The East European Plain (EEP) is characterized by relatively uniform topography with relief range from few tens of meters in flat lowlands such as Polesia or Azov-Kuban, to 100–250 m in uplands – Valdai (the highest elevation above sea level 343 m), Timan (353 m), Central Russian (293 m), Volga (351 m), Dnieper (322 m), VolhynianPodolian (471 m), Obshchy Syrt (405 m), etc. Climate changes gradually from sub-arctic in the north to temperate semi-arid in the south-east and is followed by vegetation changing southwards from tundra at the Barents sea coast to taiga, mixed and broad-leaf forests, forested steppes, steppes and semi-deserts. In the southern part of EEP the gradient of humidity is directed to south-east, so that the south-west of EEP (Moldavia, western Ukraine) belongs to broad-leaf forest zone with temperate humid climate and the south-east (the Caspian Lowland) is semi-arid with dry steppes (western Russian part) to arid with sand deserts (eastern Kazakhstan part). Temperate continental climate of EEP is characterized by cold winter with permanent snow cover and warm to hot summer when most precipitation is lost to evapotranspiration. The proportion of rain waters contributing to annual runoff decreases from 20% to 30% in the north to almost zero in the south-east while the proportion of snowmelt waters increases from N50% to almost 100% in the same direction. Modern hydrological regime over the whole EEP includes two major phases within the annual cycle: (1) high snowmelt flood in spring which constitutes from 50% (in the North) up to 90% (in the South) of annual runoff, and (2) low water season which begins from April (in the South) to July (in the North) and lasts until the next spring. Summer and autumn rainfed floods and winter thaw floods never reach magnitudes of spring floods, with the exception of rivers flowing from the Western Caucasus (the Kuban River catchment) and rivers in the very western part of EEP (e.g. the Pripyat' River system). For the most part, sediment transport

and erosion/sedimentation activity is processed during spring floods. Heavy downpours in the warm season that can cause high floods in large catchments occur only in the westernmost part of EEP (NW Russia, western Byelorussia, western Ukraine). Physiographic uniformity favors similarity in hydrological response to palaeoclimate changes. On the other hand, the great area, which totals ca. 4 million km2, and coverage of contrasting climate and vegetation zones, could have promoted individual features of paleohydrological history in different parts of the territory. To account for possible spatial specificity in hydrological responses, we first planned to construct individual fluvial chronologies for different parts of EEP. The territory was subdivided into three latitudinal zones with trinomial partitioning of each (western, central and eastern sections): - Northern EEP: the White and Barents Sea catchments; - Central EEP: the Baltic Sea catchment and the Caspian and Black Sea catchments within the humid (forest zone) and semi-humid (forested steppe zone) climate – upper and middle reaches of the Dnieper, Don and Volga River catchments; - Southern EEP: the Caspian and Black Sea catchments within the steppe zone – lower parts of the Dnieper, Don and Volga catchments and lesser tributaries of the southern seas; the boundary with central EEP is the northern limit of typical steppes at about 47°N in the south-west and 53°N in the south-east EEP. After completion of the database it became clear that northern and southern EEP are not supported by enough amounts of data to be processed separately. Nevertheless the above regional division was used to investigate spatial distribution of designated fluvial episodes. 3. Methodology 3.1. Database compilation We analyzed ca. 150 published sources to pick absolute dates on alluvial and associated (floodplain peats, slopewash loams within erosion forms) deposits. After filtering out some 10% of unreliable dates, 1170 radiocarbon and luminescence dates were included into the database. Inclusion of luminescence, presumably OSL, dates provides wider presentation of ages synchronous to high activity events as majority of radiocarbon dates rather bracket than give exact ages of such events. Each date was supplied with basic information on geographic location, geomorphological position, catchment area (as classes divisible by 10), characteristics of geological section and dated materials. Documented sections refer to fluvial forms in a wide range of catchment sizes from b1 km2 to 120,000 km2 at lower Vychegda River and 410,000 km2 at lower Don River. In the database catchment areas are presented as classes 0…6 at intervals with a 10-fold increment: 0–10°–…106 km2. The “zero class” (area b1 km2) refers to gullies and small valleys with ephemeral flow that are termed balka-valleys, or balkas (they have vegetated bottoms which distinguish them from arroyos, wadi and similar forms in arid regions). Balkas in steppes have catchment areas in the range 10°–101 km2, while catchments of the same size in the forest zone with humid climate belong to valleys with perennial flow. Dates from colluvium were included into the database but not processed in palaeofluvial estimations. Following the call of Chiverrell et al. (2011) upon more robust testing of numerical ages from individual case studies before incorporating them into regional databases, we analyzed both geomorphological position and stratigraphical context of each date to assign it any palaeohydrological meaning. Particular attention was given to dates from archaeological sites that make a noticeable portion of all published radiocarbon data from river valleys and therefore are unreasonable to be ignored. In a number of previous studies such dates were excluded from analysis to avoid biases generated by disturbance of sedimentary context or by land use (Hoffmann et al., 2008; Macklin and Lewin, 2003). We did use the dates from archaeological sites but only those appropriate to sedimentological context, i.e. dates that give age of a

Please cite this article as: Panin, A., Matlakhova, E., Fluvial chronology in the East European Plain over the last 20 ka and its palaeohydrological implications, Catena (2014), http://dx.doi.org/10.1016/j.catena.2014.08.016

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stratigraphic unit rather than age of human activity. Filtered out were all dates on artifacts and dates from materials with clear evidence of redeposition. Example is the world-known Late Palaeolithic site Mamonovaya Kurya at the Usa River (north-eastern EEP) where bones and artifacts found in terrace alluvium of channel facies are most probably redeposited by river bank erosion of a now-destructed ancient alluvial plain during terrace formation (Pavlov et al., 2001). On the other hand, bones and bone charcoal at another Late Palaeolithic site of Avdeevo at the Seim River are included into overbank alluvium and refer to a period of long break in terrace inundation. Given the possibility for re-use of old bone materials by people, dates on this material have been filtered and are now believed to represent different phases of the site occupation (Sulerzhitskiy, 2004). Burial of the cultural horizon by Holocene alluvium indicates active flooding at the site, which could not occur when the site was used for human settling. This makes ground for inclusion of the dates from the cultural horizon into the database to represent the corresponding low-flood period. At the current stage we do not use dates from the EEP north-west due to complicated history of young river-lake systems in recently glaciated regions where palaeohydrologic signals are difficult to discriminate from effects of river incision tendencies and post-glacial crust movements. For example, alluvial–soil/peat sequences have been documented in a number of sections within low terrace of the Volkhov River not far from its emptying into the Ladoga Lake indicating higher stages of river floods in the Late Holocene (Sheetov et al., 2005). When interpreting these dates we took into account the Mid Holocene transgression of the Ladoga Lake over its southern shores caused by tectonic tilting due to glacio-isostatic rebound (Dolukhanov et al., 2010).

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Therefore, high Late Holocene inundation levels in tributary valleys might have exhibited rather the lake level history than changes of river floods. To limit the temporal coverage to the post-LGM time, only the dates were included in further processing which central points after calibration were less than 20 ka BP. Total number of such dates is 983, of which 943 dates are radiocarbon and 40 are luminescence dates. They exhibit uneven geographic distribution: N 80% of dates are located in central EEP (804 dates), b15% in northern EEP (136 dates) and b5% in southern EEP (43 dates) (Fig. 1). 3.2. Indication of fluvial activity Most of previous studies used primarily sedimentological indicators of changing flood activity such as soils or peat horizons buried under overbank alluvium. In the EEP many studies have been carried out of palaeochannel dynamics exhibited in morphology of river floodplains. This geomorphological indication makes a large volume of data that may be interpreted in palaeohydrological terms: links may be suggested between flood activity and channel morphology and dynamics. We therefore use the term “palaeofluvial” that combines two interrelated aspects – river palaeohydrology and river channel morphodynamics in the past. The term “palaeofluvial event” implies both geomorphic (channel avulsion, limited lateral migrations of a channel, etc.) and sedimentological phenomena (formation of floodplain soil, its burial) that exhibit high or low fluvial activity. Local palaeofluvial event (LPE) is the one proved by a single indicator in a given geological section. When combining data at a regional scale both the accuracy of dating techniques and the nature of applied indicators do not allow recognition

Fig. 1. Location of fluvial dates in the East European Plain. Filled circles are indexed dates (dates with assigned codes of palaeofluvial events and class of palaeofluvial activity), open circles – dates without palaeohydrological interpretation but used together with indexed dates as the reference array for calculation of relative PDs.

Please cite this article as: Panin, A., Matlakhova, E., Fluvial chronology in the East European Plain over the last 20 ka and its palaeohydrological implications, Catena (2014), http://dx.doi.org/10.1016/j.catena.2014.08.016

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of individual flood or no-flood events. Such meta-analysis is intended at a probabilistic assessment of centennial-scale time intervals characterized by different fluvial status (high, low activity), which, after (Macklin et al., 2012), are designated here as palaeofluvial episodes. Regional palaeofluvial episode (RPE) is a combination of nearly simultaneous LPEs occurring in a number of locations over a region. The following indicators were used to group dates according to fluvial activity (S – sedimentological, G – geomorphological). Indicators of low activity: - sedimentological: organic horizons (soil, peat) in overbank alluvium, balka bottoms and gully fans; - geomorphological: small palaeochannels; Indicators of high activity: - sedimentological: active sedimentation on river floodplains (burial of organic horizons), balka bottoms and gully fans; - geomorphological: erosion on floodplains, in bottoms of balkas and gullies; river incision; big palaeochannels; chute cutoffs and channel avulsions. When interpreting sedimentary sequences in overbank alluvial sections two different mechanisms of changing sedimentation rates were considered. First is changing hydrological regime – this is useful signal. Second is lateral channel migrations that may cause river approaching or moving away from the studied section and change rates of overbank sedimentation. This is especially characteristic for sand-bed bedload rivers for whom usual is active migration over valley floor. Estimations of recent floodplain sedimentation rates reveal their correlation to site position relative to rivers (Belyaev et al., 2013; Golosov, 2009; etc.). If a given floodplain area is located far from active channel, sedimentation may almost stop on high topographic elements such as levees, and may be mostly organic (peat accumulation) within low elements – inter-levee hollows, silted palaeochannels. Approaching of river may resume mineragenic sedimentation, and the closer the channel is, the coarser overbank sediments are, which produces a coarsening-upward sequence above buried soils or peats at river bank exposure. In such cases dating the top of buried biogenic strata provides information of river lateral movements (channel approach to the site) but does not deal with any changes of flood height or other hydrological phenomena – see example from the middle Vychegda River (northern EEP) described by Karmanov et al. (2013). Variations of activity of erosion/sedimentation processes are thought to have been governed mainly by changes in hydrological regime and total amount of runoff. Two additional factors of changing fluvial activity in the Holocene should be considered. Firstly, climatedriven vegetation changes could regulate conditions for erosion. However no evidence exists from the most part of EEP, except for the arid south-east, of vegetation cover density changes in the Holocene that would be relevant for erosion rates or river channel morphodynamics. Secondly, human impact is known for promoting erosion/sedimentation activity. Due to low population density in the Holocene, anthropogenic factor in the EEP has been active only in the last millennium and within only patchy areas in the Dnieper and Upper Volga regions. Initial cultivation in the southern steppe regions occurred only from the 17th until the early 20th centuries. Northern region in the Barents and White Sea catchments is scarcely populated even today. Therefore we find it reasonable to consider palaeofluvial (geomorphic, sedimentological) changes in the Holocene as having been associated with changing amounts of surface runoff, particularly the height and duration of spring floods (see Section 2 for comments on contemporary hydrological regime). This supports use of the term “palaeohydrological” along with and even as some equivalent to the term “palaeofluvial”. The latter will be used in relation to the direct sedimentological or geomorphological indications – “palaeofluvial events”, while the former will be used in the context of hydroclimatic periodization – “palaeohydrological episodes, epochs, phases”.

3.3. Classification of dates According to the above indicators, particular dates were indexed in relation to corresponding LPEs as high activity dates (HA-dates) and low activity dates (LA-dates). Stratigraphic position of dated samples may differ in documented palaeofluvial signal. Two principal cases may be marked out (Macklin and Lewin, 2003; Starkel et al., 2006; Thorndycraft and Benito, 2006; etc.). Dates from mid-points of lithological units are synchronous to the LPE indicated by this unit; they are termed event-dates (e-dates). Dates from stratigraphic contacts were suggested to be referred to as change dates (Macklin and Lewin, 2003), or bracketing dates (Thorndycraft and Benito, 2006), that indicate transformation of fluvial regimes from stable to active and vice versa. We follow this approach and term such dates as change-dates (c-dates). However we believe that dates from stratigraphic contacts carry information on both the overlying/underlying unit and the unit the sample is from, i.e. on two LPEs. In the former case it is c-date, in the latter case, e-date. Change dates, according to their position at the top or in the bottom of dated unit, are pre-dates (giving knowingly older ages) in relation to an overlying unit and post-dates (giving knowingly younger ages) in relation to an underlying one. For example, a date from top of peat or soil horizon buried under overbank alluvium is indexed as e-date for the period of low floods (end of this period) and as a pre-date for the succeeding high-flood event. The offset between the date and the moment of burial is usually unknown but it is believed to be relatively short and comparable to uncertainty interval of a date (several decades to few centuries). In a few cases one date was indexed as post-date, edate and pre-date for three different LPEs. This is possible if the dated unit is thin and is believed to have formed quickly. An example would be a thin peat or gyttja horizon within actively accumulated overbank alluvium: organic horizons indicate short stabilization events that followed and preceded active alluviation events. Of the total number of entries (983), 646 dates allowed palaeohydrological interpretation and were indexed according to the type of palaeofluvial events they refer to. Of the 646 indexed dates, 542 dates indicated one LPE, 100 dates, two LPEs and 4 dates, three LPEs. In total they document 754 LPEs. About 50 dates refer to slopewash processes at valley sides, but they were not counted as LPEs and will be analyzed elsewhere. Distribution of indexed LPEs between geographic regions and corresponding catchment area is given in Table 1 (see also Fig. 1). Only the central EEP that covers mainly the upper and middle reaches of the Dnieper, Don and Volga catchments had enough LPEs to provide reliable statistics – 732, while the northern and southern zones gave 54 and 41 LPEs respectively, which is insufficient for separate processing. We therefore gave up separate treatment of different parts of the territory in favor of joint processing of all data complemented with further tracking of discovered RPEs to find their presence in different regions and in catchments of different sizes. 3.4. Data processing To sum probability density functions (PDFs) of individual dates we used the online version of OxCal 4.2 program (Bronk Ramsey, 2009) Table 1 Distribution of designated local palaeofluvial events (LPEs) by regions and catchment area. Catchment area, km2

Northern EUP

Central EUP

Southern EUP

TOTAL

b10° 10°–101 101–102 102–103 103–104 104–105 105–106 Total

– 2 2 – 1 36 11 52 (6.9%)

111 109 8 61 163 196 13 661 (87.7%)

13 16 – – 7 – 5 41 (5.4%)

124 (16.4%) 127 (16.8%) 10 (1.3%) 61 (8.1%) 171 (22.7%) 232 (30.8%) 29 (3.9%) 754 (100%)

Please cite this article as: Panin, A., Matlakhova, E., Fluvial chronology in the East European Plain over the last 20 ka and its palaeohydrological implications, Catena (2014), http://dx.doi.org/10.1016/j.catena.2014.08.016

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and the IntCal13 calibration curve (Reimer et al., 2013). For OSL dates we switched the option “Use BC/AD not BP” to “False” so that the program treated input OSL ages as calendar dates in “before present” rather than in “BC/AD” format. Before input into OxCal, we checked that OSL ages were represented as years before 1950 (most labs already report OSL ages this way) and recalculated if necessary. In processing we used the IntCal'13 calibration curve. When combining all OSL and 14C dates in a united summing project we found that the distribution tails extended to future dates by more than 4 ka. All probability densities (PDs) beyond AD 1950 had constant nonzero values of 0.06004. Integration over the whole interval with nonzero PDs, which was made as the sum of individual PDs multiplied by 5-year time increment between neighboring values, gave exactly 1025, i.e. the number of summed dates. It means that the right tail extending into the future was generated at the expense of the real summed PDF. This tail accumulated up to 25% of the total summed probability, which makes too large part to be ignored, though we found that the PDF before AD 1950 was diminished proportionally to its value, so it seems to be not crucial for application this PDF as the reference. As we did not encounter such a problem in our previous experience in processing combined datasets with the same OxCal version and IntCal'09 curve (Panin et al., 2014), we decided to check if the overlongtail effect could be evoked by using the new calibration curve. We repeated the same combined OSL-14C project with IntCal'09 curve, but the problem persisted. We decided therefore that the effect is datasetspecific. To overcome this problem we processed OSL and 14C arrays separately with subsequent manual summing of their PDFs. OSL arrays that contained dates from the last two millennia still demonstrated extending into the future when summed, but these tails were quite reasonable: not so long, small values gradually decreasing to zero. It contained b0.1% of the total summed probability and was therefore ignored (cut away). 3.5. Timescale The output from OxCal is either AD/BC (CE/BCE) or BP (years before CE 1950) calendar scale. We used the latter and added 50 years to convert it to the b2k scale (years before CE 2000). The b2k scale was initially suggested for Greenland ice core chronology (Rasmussen et al., 2006) and is now being used increasingly in a variety of dating methods (Walker et al., 2009). We find this scale convenient both for comparison to AD/BC calendar scale, which has been used in many previous studies on topic, and for correlation with global or hemispherical climatic events revealed in Greenland ice isotopic records. 3.6. Interpretation of probability density plots Theoretical analysis of the construction and interpretation of cumulative PDFs in palaeoenvironmental studies revealed a number of problems (Michczynska et al., 2003): - Non-linearity of the radiocarbon timescale, i.e. the irregular shape of calibration curve. - Preferential sampling – taking samples from places of visible sedimentation changes such as top and bottom of peat or soil layers, which may produce overestimation of PDs at selected time moments. - Decreasing availability of older deposits, or taphonomical losses – they are clearly evident from our dataset that demonstrates exponential decrease with time (Fig. 2a). Also decrease of the amount of dates in the last 500 years is evident: PD values from the last 300 years are at the same level as that of the Early Holocene. This may be explained by deliberate limitations of using radiometric dating techniques when dealing with very young sediments – “preferential unsampling” (cf. to the previous entry).

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- Insufficient number of 14C dates in some time intervals, which makes interpretation of PDF peaks and troughs unreliable. To overcome the first three problems we followed the suggestion of Hoffmann et al. (2008) and normalized summed PDFs of classified dates (HA-dates, LA-dates) dividing them by summed PDF of the total set of 983 dates (Fig. 2a). The resulting relative PDFs (RPDFs) are believed to be balanced in terms of presentation of different time intervals. Preferential sampling was also found to contribute to the shape of calibration curve in producing high, narrow peaks of summed PDF (Michczynski and Michczynska, 2006). The mechanism is that if the intervals of more frequent sampling coincide with steep slope sections of the calibration curve, the corresponding peaks of PDF are significantly amplified. We found that normalization of PDF does not eliminate this effect totally: high narrow peaks are still present in RPDF, which should be accounted for when designating paleofluvial episodes on RPDF plots. Concerning the last problem, Michczynska and Pazdur (2004) estimated the number of dates required for obtaining reliable PDF, i.e. the one that is only slightly different from PDF constructed from admittedly enough amount of dates. This number increases with the rise of standard deviation of dates. For mean uncertainty of calibrated ages of 115 years they estimate the minimum number of 200 dates required for the time interval of 14 ka and the number of 785 dates required for constructing reliable PDF for the same interval. Obviously the number of dates is proportional to the width of the time interval. For a 1000-year interval the minimum number would be 14 dates and the reliable number, 56 dates. In our array mean uncertainty of radiocarbon dates indexed with palaeofluvial codes (i.e. participating in PDF processing) is 119 years (626 dates totally). Inclusion of luminescence dates raises mean uncertainty up to 142 years (646 dates totally). As most luminescence dates are pre-Holocene or Early Holocene, mean uncertainties for the Middle and Late Holocene dates are of the same order as in the test series by Michczynska and Pazdur (2004) and we therefore can use their estimations of number of required dates. For the Early Holocene and pre-Holocene this number must be higher because of higher values of uncertainties. Time-dependent distribution of indexed dates from our collection, i.e. the dates that were assigned palaeofluvial interpretation, is plotted in Fig. 2b. Only low activity e-dates in the last 2 ka fit the criterion of reliability n ≥ 56 dates per millennium. Minimum number criterion of n ≥ 14 dates per millennium is satisfied by low activity e-dates in the last 9 ka and by high activity e-dates in the last 4 ka. Nevertheless, if e-dates are combined with c-dates, then the HA-dates fit the minimum number criterion for the last 6 ka and in selected intervals in the Late Glacial, while combined pre-Holocene LA-dates older than 9 ka do not fit this criterion in any interval. Based on these estimations, we decided that acceptable results cannot be achieved separately from e-dates or cdates, but all types of dates should be combined when designating particular episodes. Also we realized that in the Holocene, reliable periodization may be extracted from PDF plots only in the last 4 ka. Any division within the 4–9 ka interval would be less trustworthy. Periodization in the 9–12 ka interval would not be reliable and should be considered as tentative estimates. Available data are not enough at all for any division of the pre-Holocene time. We use pre-Holocene PDF plots only as a whole to make comparison of the Late Glacial to the Holocene in a very general form. Chiverrell et al. (2011) list a number of problems that undermine the use of cumulative PDFs as hydroclimatic proxies. After the elucidation by Macklin et al. (2011, 2012), some of these concerns are still relevant for our study. Chiverrell et al. (2011) point that databases may incorporate differing interrelations relationships between the measured ages and corresponding events, with variable temporal lags but all mixed together in the same analysis. Obviously, such mixing would decrease reliability of resulting cumulative distributions. To avoid it in our study we construct individual PDFs for e-dates and c-dates (pre- and post-dates) and analyze them separately to detect palaeohydrological variability.

Please cite this article as: Panin, A., Matlakhova, E., Fluvial chronology in the East European Plain over the last 20 ka and its palaeohydrological implications, Catena (2014), http://dx.doi.org/10.1016/j.catena.2014.08.016

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Fig. 2. Time-dependent distribution of dates in the database. (a) Probability density plot for all dates, including indexed dates and dates without palaeofluvial interpretation. PDF of total array of dates is used as the reference for normalization of indexed dates' PDFs. (b) Quantity of different types of indexed dates per 1000 years.

Relatively low peaks in e-date PDFs were interpreted as palaeohydrological episodes only in case if they were supported by bracketing peaks of pre- and post-dates, or at least one of them. Few episodes not documented by e-dates were designated solely from pre- and postdate PDFs, and their age was derived from bracketing peaks, usually as the middle between them. Temporal resolution of such chronology excludes detection of individual fluvial events, but rather provides fluvial variability at multi-centennial scale as pointed out by Macklin et al. (2012). Chiverrell et al. (2011) also proposed wider use of data on river/gully aggradation and incision phases and palaeochannel development based on models of reach-scale fluvial landform evolution. In our study this suggestion is met by analysis of geomorphological indicators of palaeofluvial change that complement traditionally used sedimentological indicators; see the list of applied indicators of fluvial activity in Section 3.2. 4. Results 4.1. High and low activity probability density plots PDF plots were constructed separately for all types of HA-dates and LA-dates (Fig. 3). LPEs of both high and low activity are present within all time intervals on the plot. Graphs exhibit rhythmic variations. Peaks and troughs of high and low activities are generally opposite to each other, which supports the periodization approach. Rhythmicity is best expressed in the low activity graphs, which reflects to some extent its better quality: 80% of its dates are e-dates. For the high activity series

the e-dates constitute only about a half of the total quantity. This makes the temporal pattern not so clear and stresses the need to use both edates and c-dates for construction of periodization. 4.2. Palaeohydrological periodization The succession of peaks and troughs on probability density graphs was used to mark intervals of high and low fluvial activity. The complex shape of PD graphs compels designation of a hierarchy of events. Three hierarchical divisions were discerned: palaeohydrological episodes (centennial scale), phases (millennial scale) and epochs (Marine Isotope Stages (MIS) or considerable part of one). High activity and low activity episodes (HA-episodes, LA-episodes) were detected from the relative PD graphs (Fig. 3). To filter out insignificant or occasional peaks we analyzed both relative and absolute PD distributions and used the following criteria for selection: 1) The peak rises above the background by ≥ 0.1 in relative PDs by ≥ 0.01 year−1 in absolute PDs and it is not less than a centurywide at the base. It was experimentally found that together the latter two conditions guarantee that the peak is formed from no less than two age determinations; in case of doubt we checked it manually with the database. 2) Dates that form the peak are found in not less than two distant locations, which demonstrates the non-local character of an event. The majority of episodes correspond to a particular peak at the LA or HA RPD graph. However not only e-dates but also c-dates (pre- and post-dates) were taken into account when designating valuable peaks.

Please cite this article as: Panin, A., Matlakhova, E., Fluvial chronology in the East European Plain over the last 20 ka and its palaeohydrological implications, Catena (2014), http://dx.doi.org/10.1016/j.catena.2014.08.016

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Fig. 3. Relative probability densities of high activity (a) and low activity (b) dates. Regional palaeofluvial episodes are marked by arrows and indexes: orange – high activity (H-events), blue – low activity (L-events), green – complex activity (C-events). For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.

Few HA episodes were distinguished by pre- and post-dates only, which is reasonable given the significant role that change dates play in detecting HA episodes: they make 46% of the total massif of HA dates against only 14% in case of LA dates. HA and LA episodes were detected as rises in corresponding relative PD graphs of e-dates. Two types of such peaks were found. Most of HA peaks corresponded to falls in LA graphs and vice versa. In few cases rises of both HA and LA coincided, such as around 3000, 4500, 7500 and 9000 years b2k. Such episodes were separated into an individual group as combined, or contrast activity episodes – CA-episodes. Episodes are presented as approximate central points of centennialscale intervals. Rises in PD graphs have in many cases considerable width and more than one peak. Possible reasons may be: (a) really long duration of an episode and its complicated temporal pattern; (b) short term episode which is presented by wide peak due to its non-synchronism over the territory; (c) low accuracy of dates documenting a single event and effects of the shape of calibration curve and preferential sampling (see Section 3.6). Palaeofluvial phases were distinguished in HA–LA difference and averaged graphs (Fig. 4). Averaging was made by moving window of a 500-year width. Averaging was produced not only by e-dates but by total massifs of LA and HA dates including both e-dates and c-dates, 372 and 382 ages respectively. We did that first of all because of large contribution of change dates into the HA massif. Non-inclusion of such dates could lead to significant information losses. Complementing of averaged massifs by change dates produced additional smoothing of distributions especially in the HA graph, where some troughs became blurred. As this blurring was probably caused by large time lags between the c-dates and indicated events, very likely longer than the averaging window in many cases, we were appealing to original PD graphs when distinguishing the PH stages. In the Holocene, difference between HA and LA PD is mostly negative, which reflects the higher availability of evidences of LA-episodes, mostly buried organic horizons, for designation and being dated by radiocarbon, the more popular dating technique. Therefore simple numerical approach is not reasonable when distinguishing between HA and LA hydroclimatic phases and episodes. Rather, we followed relative

oscillations of HA and LA graphs. However obvious is the prevalence of HA indicators in pre-Holocene time after the Last Glacial Maximum (LGM). This provides ground to distinguish the Holocene (0–11.7 ka b2k) and post-LGM part of MIS 1 (11.7 – ca. 18 ka b2k) as separate palaeohydrological epochs with significantly different hydrological regimes. 4.3. Palaeofluvial episodes in terms of indicator types, geographic regions and catchment size The full list of designated epochs, phases and episodes is presented in Table 2. Phases are numbered one by one so that odd numbers are always assigned to HA-phases and even numbers to LA-phases. HA- and LA-episodes are identified separately within each phase. CA-episodes as having both HA and LA features are numbered in the same order with both HA- and LA-episodes. Totally, 19 palaeofluvial episodes were detected in the Holocene, of which 7 are high activity, 8 are low activity and 4 are contrast, or combined, activity episodes. To evaluate the reliability of detected episodes we analyzed their representation by different types of indicators (sedimentological, geomorphological), presence in different regions (northern, central, southern EEP) and manifestation in catchments of different sizes. Intensity of particular episodes was estimated from the height of respective peaks in RPD plots. Values in Table 2 were obtained as summed RPDs of all types of dates (e-dates, pre-dates, and post-dates) that refer to each episode. For CAepisodes both high- and low-activity RPDs are presented. In terms of indicator type, more than a half of all episodes are better expressed by sedimentological indicators, some one third by both indicators equally, and only a few where geomorphological indicators dominate (for C-episode both high- and low-activity indicators were considered). Half of C-episodes exhibit contrast pattern with high activity features demonstrated by geomorphic indicators and low activity – by sedimentological ones (C3.4 – 3000 b2k, C4.2 – 4500 b2k). Probably this may help to better understand the nature of these episodes. All detected episodes are exhibited in the central EEP and only some of them are found in northern or southern regions. When interpreting this fact one should take into account that geographic distribution of

Please cite this article as: Panin, A., Matlakhova, E., Fluvial chronology in the East European Plain over the last 20 ka and its palaeohydrological implications, Catena (2014), http://dx.doi.org/10.1016/j.catena.2014.08.016

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Fig. 4. Variations of high and low fluvial activity PDs and palaeohydrological phases in the Holocene. (a) Difference between high and low activity PDFs and the Holocene palaeofluvial phases and events. Larger circles are the most pronounced events (cf. Table 2). (b) Moving window averages of high and low activity PDFs. Colored background marks the Holocene palaeofluvial periodization: red (dark gray in printed version) are activity phases, blue (light gray) are stability phases. For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.

episodes is distorted due to the initial data lack both in the northern and southern EEP. Therefore absence of particular episodes in the northern or southern periphery of the plain may not provide sufficient evidence as to their real geographic coverage. In this respect more interesting are the episodes exhibited in all the regions, which probably represent their real distribution over the whole EEP. Only one such episode is found: L4.1 – 4000 b2k. Four episodes are found both in central and southern EEP (L1.1 – 400 b2k, H1.2 – 600 b2k, L2.1 – 1300 b2k, H6.1 – 6200 b2k) and two episodes – in both central and northern EEP (L6.4 – 8000 b2k, H7.2 – 10600 b2k). C-episodes demonstrate different patterns: some are expressed only in central EEP (C3.2 – 3000 b2k); others may exhibit different indicators in different regions. Nevertheless, all C-episodes are well represented in both high- and low-activity indicators in the central EEP. This means that the complexity of these episodes does not result from incomplete spatial coverage of data and further additions to the database are unlikely to split these episodes into separate high- and low-activity episodes in different regions. When considering representation of palaeofluvial episodes in different catchment size classes, we account for low contribution from medium catchments (n × 101–n × 103 km2) that refer only to 9% of all detected LPEs while small (b 101 km2) and big (n × 103–n × 106 km2) catchments give 33% and 58% LPEs respectively (see Table 1). We will therefore consider small and big catchments only. Most episodes are represented in both size classes, except for the two oldest ones, which may result from their weak evidence on the whole. Only few episodes may be mentioned for their noticeably stronger presence in big catchments (L2.1 – 1300 b2k, L6.1 – 5700 b2k), and no episodes significantly prevail in small catchments. It may indicate that generally the detected

palaeofluvial episodes acted over a wide range of catchment sizes and were therefore likely to have resulted from spring runoff changes that spread over large areas rather than from changes in storm magnitude and frequency that, in terms of individual storm, cover only small areas. However episodes C3.2 (3000 b2k) and C4.2 (4500 b2k) demonstrate a kind of asymmetry in activity classes by catchment size: high activity features are better expressed in small catchments while low activity features concentrate in big catchment in the former and in small-medium catchments in the latter case. This may indicate warm period storms rather than spring snowmelt contributions for the occurrence of these episodes. 5. Discussion 5.1. General hydroclimatic tendencies in the post-LGM time The constructed chronology for the indicators of high and low fluvial activity demonstrates that not only thermal but also hydroclimatic regime had changed significantly in the EEP at the MIS 2/MIS 1 boundary. Total amount of surface runoff in the Holocene was considerably lower compared to that in the post-LGM part of MIS 2. The main indicator of high river discharges between LGM and the onset of the Holocene is occurrence of large palaeochannels (macromeanders) found almost all over the EEP (Panin et al., 1999) but dated predominantly in the central EEP (Borisova et al., 2006; Panin et al., 2013; Sidorchuk et al., 2009, 2011; etc.). Another line of evidence comes from active gully erosion/ sedimentation in the end of the Late Pleniglacial (Bessudnov et al., 2013). The whole set of dates permits dating of the onset of this high

Please cite this article as: Panin, A., Matlakhova, E., Fluvial chronology in the East European Plain over the last 20 ka and its palaeohydrological implications, Catena (2014), http://dx.doi.org/10.1016/j.catena.2014.08.016

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Table 2 Magnitudes of the Holocene paleofluvial episodes in terms of indicator type, geographic regions and catchment size, expressed as relative probability densities (RPD) of associated eventand change-dates. Phase, time (ka b2k)

0 (LA) 0–0.15 1 (HA) 0.15–0.9

2 (LA) 0.9–1.9 3 (HA) 1.9–3.5

4 (LA) 3.5–4.6

5 (HA) 4.6–5.5 6 (LA) 5.5–8.5

7 (HA?) 8.5–11.7

Episode

Indicators

Regions

Catchment sizes

Index

Central point (years b2k)

Sed

Geo

N

C

S

Small

Medium

Big

H1.1

250

0.5

0.1

–

0.6

–

0.2

0.2

0.2

L1.1 H1.2 L2.1

400 600 1300

0.5 0.5 0.7

– 0.2 0.1

– – –

0.5 0.5 0.8

0.1 0.2 0.1

0.2 0.3 0.1

– 0.1 0.2

0.3 0.3 0.6

H3.1

2200

0.3

0.4

–

0.6

–

0.2

0.1

0.4

L3.1 С3.2

2500 3000

L4.1

4000

0.4 H– L 0.5 0.7

– H 0.4 L– 0.1

– H– L– 0.2

0.4 H 0.4 L 0.5 0.5

– H– L– 0.1

0.1 H 0.4 L 0.1 0.3

0.1 H– L 0.1 –

0.2 H– L 0.3 0.5

C4.2

4500

H5.1

5100

H 0.1 L 0.6 0.2

H 0.4 L– 0.1

H– L 0.1 –

H 0.5 L 0.5 0.3

H– L– –

H 0.3 L 0.3 0.1

H 0.1 L 0.2 –

H 0.1 L 0.1 0.2

L6.1

5700

0.6

–

–

0.6

–

0.1

0.1

0.4

H6.1 L6.2 C6.3

6200 6600 7500

H7.2 L7.2 H7.3

10600 11200 11600

– – H– L 0.3 0.3 H– L 0.3 0.2 – –

0.4 0.6 H 0.3 L 0.7 0.8 H 0.4 L 0.3 0.2 0.2 0.2

0.2 0.2 H 0.2 L 0.2 0.7 H 0.2 L 0.1 0.1 – –

– 0.1 H– L 0.2

8000 9000

0.2 – H 0.2 L 0.6 0.3 H 0.3 L 0.2 0.3 – 0.2

0.1 – H 0.1 L–

L6.4 С7.1

0.3 0.6 H 0.3 L 0.4 0.8 H 0.2 L 0.4 0.1 0.2 0.1

0.3 0.3 H 0.2 L 0.6 0.4 H 0.3 L 0.5 0.3 0.2 0.2

H 0.1 L– – – –

H– L– – – –

Notes: 1. 2. 3. 4.

Marked in bold are the most pronounced episodes, which total RPD, i.e. RPDs summed by indicators, or regions, or catchment sizes, is not less than 0.7. RPDs include both e-dates and c-dates linked to a particular event, which explains why total RPD of an event may principally exceed 1 (e.g., L6.4). Catchment size: small – b101 km2, medium – 101 ÷ 103 km2, big – 103 ÷ 106 km2. Abbreviations: Palaeohydrological phases: LA – low fluvial activity, HA – high fluvial activity. Palaeofluvial episodes: L – low fluvial activity, H – high fluvial activity, C – combined (or contrast) fluvial activity. Indicators: Sed – sedimentological, Geo – Geomorphological. Regions: C – central, N – northern, S – southern EEP.

runoff period at ca. 18 ka b2k. The PD graph for high activity dates exhibits two rises in pre-Holocene time (Fig. 3), but the overall number of dates is too small still to construct any reliable division of this epoch into phases and episodes. Also, there is no confidence in synchronism of these rises of fluvial activity over the whole EEP. At this stage we can only certify the two palaeohydrological epochs characterized by completely different states of hydrological systems – the post-LGM part of MIS 2 (18–11.7 ka b2k) and the Holocene (11.7–0 ka b2k). Considerable increase of runoff in the Late Glacial compared to the Holocene established here by geomorphic and sedimentological indicators is corroborated by quantitative estimates of runoff layer from pollen data. Modern analogs of fossil floras extracted from peat and gyttja infilling of a large palaeochannel of the Seim River (the middle Dnieper River catchment) were used by Borisova et al. (2006) to estimate runoff depth since 17 ka b2k. Annual runoff depth was estimated to some 300 mm in the interval 17–15 ka b2k and around 200 mm in 14–12 ka b2k, which is some 2.5 and 1.5 times greater than that at present. Similar estimates for the Moskva River where the present-day runoff is 235 mm/year provided palaeorunoff values in the range 300–450 mm/year, or 30–90% higher than that at present (Sidorchuk et al., 2009). Palaeorunoff at 14.5 ka b2k was estimated at about 240 mm/year, which equals the present-day value, and 300 mm/year in 13–14 ka b2k.

The Early Holocene until 8.5 ka b2k was formally marked as the high activity phase (phase 7) because the HA–LA PD difference for this interval ranges between 0…+ 0.2, which is characteristic for high activity phases in the Mid and Late Holocene (Fig. 4a). However the sum of high- and low-activity RPDs is around 0.3 during much of this interval (Fig. 3), which means that palaeohydrological interpretation was assigned for only one third of all dates from that period. This is the Holocene lowest proportion of interpretable dates, which may indicate some unusual conditions during that period. We assume phase 7 to be the transitional period characterized by fluvial system relaxation after extremely high runoff in the Late Glacial. Diminished Early Holocene rivers developed within valley bottoms overwidened by migration of Late Glacial macromeanders. Reorganization of river channels hindered both sedimentological and geomorphological signals of changing hydrological regimes. Palaeohydrological indicators become more clear by 8.5–9 ka b2k, which may mean that fluvial systems became balanced with new amounts of runoff: in the last 8.5–9 ka b2k the proportion of interpretable dates estimated as sum of HA and LA RPDs is 70–80% and higher (Fig. 3). The Mid Holocene is the longest period of low fluvial activity that lasted about 3 ka (8.5–5.5 ka b2k). A rise in fluvial activity began after this. The last 5.5 ka exhibits contrast (at the Holocene scale) changes of high and low activity. Consequently, the Holocene may be divided

Please cite this article as: Panin, A., Matlakhova, E., Fluvial chronology in the East European Plain over the last 20 ka and its palaeohydrological implications, Catena (2014), http://dx.doi.org/10.1016/j.catena.2014.08.016

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into three parts according to palaeofluvial activity: Early Holocene – transitional period of fluvial system reorganization with obscure palaeohydrological indication (PH phase 7, 11.7–8.5 ka b2k), Mid Holocene – the prolonged period of fluvial quietness (PH phase 6, 8.5–5.5 ka b2k) and the second half of the Holocene since 5.5 ka BP with succession of contrast high- and low-activity phases and overall tendency to growing peak activities. These general tendencies correspond to earlier reconstructions of climate humidity and runoff based on pollen data, especially that concerning the Middle Holocene. Khotinskiy (1989) designates the end of the Atlantic period in the Upper Volga Region as one of the driest intervals in the Holocene. In the Volga River catchment, all pollen-based estimations demonstrate lower than the present runoff values during the Holocene thermal optimum in the Late Atlantic period 6–7 ka b2k, which corresponds to the second half of our low activity phase 6. In the middle Oka River catchment (the second largest tributary of Volga) the estimated drop of runoff in the Late Atlantic ranges from 5– 10% (Vinnikov and Lemeshko, 1987) to 20–25% (Efimova, 1987; Velichko et al., 1988). In the middle Seim River (the middle Dnieper River catchment) modern analogs of palaeofloras provide the palaeorunoff estimate of 90 mm/year in the Late Atlantic, which is 30% less than the present-day value of 125 mm/year and 30–45% less than runoff estimates for the earlier Holocene intervals (Borisova et al., 2006). 5.2. Comparison to palaeosoil chronologies Most advanced in the region are palaeopedological schemes constructed from radiocarbon dating of buried floodplain and balka (small dry valley) bottom soils. In the Upper Volga and Oka basins, Alexandrovskiy (Alexandrovskiy and Alexandrovskaya, 2005; Alexandrovskiy and Krenke, 2004) distinguished 6 Holocene soilforming phases, S-Phases, alternating with 5 phases of intensive alluvial sedimentation, A-phases (Fig. 5d). Sycheva (2006) used ca. 120 dates on buried soils and ca. 40 dates on alluvium to distinguish 7 pedogenic Pd-phases and 5 lithogenic L-phases in the middle sector of the EEP between 47 and 58°N (Fig. 5e). Datasets used in both studies widely intersect with one another; hence the designated phases are very similar. Most of these dates were included also in our database and thus participate in construction of our scheme. Therefore good conformity of all the chronologies is predestined by using common data for their construction. However the new chronology proposed here is founded on a wider sedimentological and geomorphological basis. Therefore we find it worthwhile to compare it to the palaeopedological chronology, given that soil-forming phases have been widely used as a chronological instrument in palaeoclimate, palaeogeomorphological, archaeological and other kinds of research in the EEP. The scheme suggested in this study is least similar to palaeopedological schemes in the Early Holocene. Our transitional phase 7 corresponds mostly to stability phases Pd-6 and S-6 in the above studies. In the above, we already stressed that definite palaeohydrological interpretation of this period is hindered by its transitional nature, strong reorganization of fluvial systems. Probably, palaeopedological data give reasons for treating this period rather as low-activity than high-activity phase. On the other hand, stability phases Pd-6 and S-6 are grounded on very few dates from Early Holocene buried soils and thus have limited reliability. Also, HA- and CAepisodes within our phase 7 correlate well with sedimentation phases of Alexandrovskiy and Sycheva: H7.3 and H7.2 episodes (11,600 and 10,700 b2k) together correspond to L-6, and C7.1 episode (9000 b2k)

with rather distinct high-activity signal (Table 2) corresponds to phases A-5 and L-5. Probably, it would be reasonable to divide phase 7 into several HA- and LA-phases, but we avoid doing it at the current state of our understanding of this period as it is based on too limited data. In the Mid and Late Holocene, there is much correspondence between all schemes. Our LA-phase 6 corresponds to soil-forming stability phases 4 and 5. In the interval 7000–7500, the soil-forming phases are divided by the active sedimentation phase A-5, or L-5. Most probably it corresponds to our combined-activity episode C6.3 (7400 b2k). High-activity episode H6.1 (6200 b2k) is not reflected in paleopedological schemes. HA-phase 6 with HA-episode H5.1 (5100 b2k) is equivalent to sedimentation phases A-3 and L-3. Also, LA-phase 4 corresponds distinctly to soil-forming phases S-3 and Pd-3. Probably, the combined episode C4.2 (4500 b2k) that occurred in the very beginning of this phase reflects the transitional nature of this time or non-synchronous shift to low flood activity over the territory. Given that, there is an alternative to link this episode to the previous active phase thus extending it 4300–4400 b2k. Soil-forming phase 3 in its both variants (S-3, Pd-3) extends to ages younger than 3000 b2k and overlaps with our HA-phase 3 and its combined episode C3.2 (3000 b2k). We find it reasonable to link this episode along with the whole phase 3 to sedimentation phase 2 in palaeopedological schemes. Sedimentation phase 2 (A-2, L-2) in these schemes is only 500 years long, which is three times as short as our HA-phase 3. Probably this is because more comprehensive account for high-activity markers while paleopedological schemes base mostly on dating of buried soils. Activity phase A-2/L-2 is dated around 2500 b2k. In our scheme, concurrent to it is the low activity episode L3.1 (2500 b2k) and the highest activity occurs few centuries later – episode H3.1 (2200 b2k). This high-activity episode overlaps with the very beginning of the next soil-forming phase, which starts some earlier than the corresponding stability phase 2 in our scheme. Dynamics during the Current Era is much similar in all schemes. The 1st Millennium CE belongs to soil-forming phase S-2/Pd-2 and lowactivity phase 2, which is one of the most pronounced stability phases in the Holocene. Phase 2 starts later than the corresponding phase S2/Pd-2 (2000 vs. 2300–2400 b2k), but ends within the same interval between 800 and 1000 b2k. In the last Millennium palaeopedological schemes distinguish one phase of intensive sedimentation between 500 and 900 b2k followed by the contemporary soil formation phase. In our scheme this activity phase is longer and has more complicated temporal pattern. It consists of two high activity episodes at 600 b2k (H1.2) and 250 b2k (H1.1) separated by a low activity episode at 400 b2k (L1.2). In the study of the Late Holocene pedological– sedimentological rhythms during MCO-LIA, Sycheva (2011) distinguishes the weak pedogenic phase on floodplains in the 17th c. AD, which is equivalent to our low activity episode L1.1 (400 b2k). The contemporary stability phase reflected in the overall blanketing of floodplains by surficial alluvial-type soil, is probably rather short and covers the last one–two centuries only. Its chronology cannot be established by direct 14C or OSL dating because of too young ages, but it follows from the properties of surficial floodplain soils and historical sources. The above comparison shows that our scheme is rather similar to existing palaeopedological schemes in low activity, or soil-forming, phases. It reflects both intersection of the data used and better availability evidences of low flood evidences (buried soils, peats) for dating. In high-activity phases differences exist both in duration of phases and in timing of peak events. These dissimilarities come presumably from much higher abundance of activity dates involved in our study

Fig. 5. Correlation between different hydroclimatic phenomena in the East European Plain. Palaeofluvial activity (this study): a, b – RPDs of high and low fluvial activity indicators, c – palaeohydrological phases and events; larger circles are most pronounced events (cf. Table 2). Soil forming, or pedogenic, and alluviation, or lithogenic, phases: d – after Alexandrovskiy and Krenke (2004), Alexandrovskiy and Alexandrovskaya (2005); e – after Sycheva (2006). Lake level changes: f – lake level status in the Upper Volga River basin (after Tarasov et al., 1997); g – the Caspian Sea level changes through the Holocene (after Kroonenberg et al., 2008; Rychagov, 1997a) and freshening phases in the Southern Caspian Basin (after Leroy et al. (2007)); h – the Caspian Sea level changes in the last millennium (after Naderi Beni et al. (2013) and Rychagov (1997b); since 1837 – instrumental measurements).

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Please cite this article as: Panin, A., Matlakhova, E., Fluvial chronology in the East European Plain over the last 20 ka and its palaeohydrological implications, Catena (2014), http://dx.doi.org/10.1016/j.catena.2014.08.016

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compared to studies of palaeopedologists. Comparison reveals also that our C-episodes that exhibit a mixture of high- and low-activity phenomena correspond rather to active sedimentation than to stability soil-forming phases in paleosoil stratigraphy. Probably this is due to non-synchronism of activity and stability phases in different regions that could lead to combining both types of evidences in the same time interval. More data is needed to construct individual regional schemes that would separate activity and stability signals more definitely. 5.3. Comparison with lake level data The only systematic data on lake levels from the central EUP exist for the Upper Volga region. These data are collected by Tarasov et al. (1997) and presented at an increment of 500 14C years as percentage of lakes with different level status: high, medium and low. We transformed the 14C intervals into the calendar scale using IntCal13 and then to the b2k scale (Fig. 5f). Lake levels demonstrate the overall tendencies that in very general resemble the Holocene tendencies of fluvial activity changes. Lakes have the highest status in the Early Holocene, then drop to the lowest status in the Mid Holocene and then rise by the Late Holocene. Nevertheless, the particular fluvial extremes are either not presented or not coinciding to that in the lake level graph. The Holocene lowest lake level status is expected to occur within the Holocenelongest period of fluvial activity – phase 6 (5500–8500 b2k), but it is shifted to younger ages and becomes synchronous to the high-activity phase 5 around 5000 b2k. This discrepancy may be caused by relatively low precision of lake level chronology that was established mostly from interpretation of pollen diagrams with rather low participation of radiocarbon dating. Sharp fluvial changes in the last 2000 years are not reflected in lake level data. The reason comes probably from the open character of all lakes in this humid-climate region, which makes them less sensitive to relatively short climate variations. Nevertheless, the Holocene-long tendencies are exhibited in lake level data quite distinctly. More relevant data exist on level fluctuations of the Caspian Sea (CS), which is a closed lake and thus it is more sensitive to the water balance changes. Instrumental observation data prove that the CS level changes are governed mostly by cumulative effect from variations of the Volga River runoff (Arpe and Leroy, 2007; Mikhailov and Povalishnikova, 1998). Therefore the CS level behavior is the proxy for runoff changes within the central EUP where the Volga River receives the most part of its waters. We used the CS level history reconstructions by Rychagov (1997a) and Kroonenberg et al. (2007, 2008) and designation of the CS freshening phases made by Leroy et al. (2007) (Fig. 5g). For the last millennium we referred to reconstructions based on historical data (Naderi Beni et al., 2013; Rychagov, 1997b) (Fig. 5h). When comparing terrestrial and marine records one should account for difficulties in calibration of radiocarbon dates obtained from marine carbonates. Different researches prefer either using uncalibrated radiocarbon timescale or applying correction procedures, which may be dissimilar in different cases. Graphs in Rychagov (1997a) and Kroonenberg et al. (2008) are presented in uncalibrated 14C years. To present in the b2k timescale we first digitized and calibrated their critical points. Both curves are based on dates from shells; therefore the challenge is which calibration curve should be taken. Rychagov's dates are conventional dates without correction for isotope fractioning. Given their δ13C values around zero and the reservoir effect for the CS about 300–400 years, Karpytchev (1993) proposed for such dates that corrections for isotope fractioning (adding ~400 years) and for reservoir effect (subtracting 300–400 years) closely compensating each other. Hence we calibrated the Rychagov's curve using the terrestrial calibration set IntCal13. The CS level curve by Kroonenberg et al. (2008) is based on AMS dates on in situ shells. Given that AMS dates automatically include the δ13C correction, we calibrated this set using the Marine13 curve, for which offsetting from the IntCal13 curve depends on time but is usually in the range 300–400 years. After calibration we added 50 years to shift

to the b2k scale. Leroy et al. (2007) dated bulk carbonates and in their correction to measured 14C activities accounted for both the difference in 14C content in the atmosphere and in surficial waters (analog for the reservoir effect correction) the proportion of detrital and authigenic fractions of carbonate assuming zero 14C activity for the former. Together both corrections gave the 800–900-year shift to younger ages. Karpytchev (1993) estimated for shelf carbonates even greater ±100 years. Evidently, several hundred years may be a real estimate for precision of dates obtained from bulk carbonates. The first half of the Holocene exhibits poor similarity between the CS levels and fluvial activity data. Occurrence of the deep Mangyshlak regression at the onset of the Holocene (Fig. 5g) is a bit contradictory to the high lake level status in the Upper Volga region (Fig. 5f) and high fluvial activity and active sedimentation episodes over the central EUP (Fig. 5a–c). Probably this is due to the transitional character of the Early Holocene fluvial and lacustrine system development when traces of high activity are rather due to reorganization of geomorphic systems than to higher amounts of runoff. The Holocene highest levels at the highest stage of the Novo-Caspian transgression, according to Rychagov (1997a), fall into the Holocene-longest phase of low fluvial activity (phase 6) but can be correlated to high activity episodes within this phase – C6.3 (7500 b2k) and H6.1 (6200 b2k). The high-activity phase 5 is not reflected in the CS level reconstructions both by Rychagov (1997a) and by Kroonenberg et al. (2008). Much more similarities exist in the second half of the Holocene. The CS lowstand around 4000 b2k corresponds to the fluvial stability phase 4. Fluvial activity phase 3 correlates to highstands in both Rychagov's and Kroonenberg's curves. Nevertheless, the timing of the peak stages differs greatly: the highest levels occur at 3000–3500 b2k according to Rychagov (1997a) and between 2000 and 2500 according to Kroonenberg et al. (2008), the latter being synchronous to our high activity episode H3.2 (2200 b2k). We consider the Kroonenberg's dating more reliable as it is based on ages from in situ shells and the number of dates is much greater. In their other paper Kroonenberg et al. (2007) propose that the highstand was reached around 2600 BP and continued until 2200 BP. Nevertheless the calibrated dates convince that at 2600 BP the sea level was below −27 m and all dates on samples above − 25 m lie within the range 2000–2300 BP (see Table 1 in Kroonenberg et al., 2007). The next low fluvial activity Phase 2 corresponds to the so called Derbent regression of the CS. According to Rychagov (1997a,b) the lowest levels were reached around the 8th c. AD, or 1300 b2k. In the Kroonenberg's curve this minimum is much lower and extends into the 10th c. AD, 900–1000 b2k. This looks too late given the majority of the CS level reconstructions. If the reservoir effect not accounted for, this minimum would be some 400 years earlier, which corresponds better to other reconstructions and to the fluvial activity data (low activity episode L2.1, 1300 b2k). Probably, this reflects some uncertainties in radiocarbon calibration (see discussion in the above). Leroy et al. (2007) used palynological and dinoflagellate data to reconstruct the Caspian Sea salinity changes and deduce the changes of river inflow into the Caspian Sea. They found two phases of lesser salinity and stronger river inflow in the second half of the Holocene: the major phase started before 5.45 and ended by 3.9 cal ka BP (N 5500– 3950 b2k), and the second phase, less important and shorter, occurred at ca. 2.1–1.7 cal. ka BP (2150–1750 b2k). Leroy et al. (2007) assume some contribution from the Uzboy River into the first freshening phase, but they also account that the reliable chronology for the Uzboy flowing into the Caspian Sea has not been established yet. Therefore one could propose that the Volga River runoff was the major source of freshwater in the second half of the Holocene like it does now. The N5500–3950 b2k high river inflow and sea freshening phase correlates well with our activity phase 3 (5500–4600 b2k), which is missed in the CS palaeolevel data (Fig. 5g). The freshening phase extends also into the stability phase 4 (4600–3500 b2k) and ends around our low activity episode L4.1 (4000 b2k). The second freshening phase starts close

Please cite this article as: Panin, A., Matlakhova, E., Fluvial chronology in the East European Plain over the last 20 ka and its palaeohydrological implications, Catena (2014), http://dx.doi.org/10.1016/j.catena.2014.08.016

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to our HA-episode H3.1 (2200 b2k) and extends a little into the fluvial stability phase 2. Given the uncertainties with dating bulk carbonates discussed in the above we consider the coincidence of both freshening phases with periods of high fluvial activity quite satisfactory. For the last millennium we could compare our results to historicalbased reconstructions of the CS level that are devoid of calibration problems (Fig. 5h). After the Derbent regression, Rychagov (1997b) distinguishes two highstands in 14th–early 15th and in 17th–18th centuries separated by a lowstand in the 16th century. Similar phases are proposed in the recent paper by Naderi Beni et al. (2013), but their peals are significantly higher and the first highstand occurs some earlier, at the 13th–14th century boundary (Fig. 5h). Both highstands may be correlated to our high activity episodes H1.2 (600 b2k) and H1.1 (250 b2k), the lowstand – to the low activity episode L1.1 (400 b2k). One can conclude that in the last millennium the reconstructed CS palaeolevel history is closely connected to the fluvial history over the sea catchment. The above comparison reveals rather good similarity between the terrestrial fluvial phases, that may be interpreted in terms of changing amounts of river runoff, and the level changes in a closed lake that integrates water balance of the large part of EUP. Both activity/stability phases and transgression/regression cycles of the CS exhibit similar successions that are synchronized rather well. The lack of coincidence between phases of fluvial activity and the corresponding level change/ water freshening phases of the CS may occur because of the uncertainties in calibration of radiocarbon dates on marine carbonates. Similarity is much poorer in the first half of the Holocene. It reflects either the lower level of our knowledge of both marine and terrestrial dynamics, or our underestimation of real complexity of water balance formation in the past, or both. In either case, this is a challenge for for further study. 5.4. Comparison with palaeofluvial data from central and western Europe Holocene hydroclimates of European mid-latitudes from the British Isles to Urals were to a great extent governed by common climatic mechanisms generated in North Atlantics, such as frequency and power of cyclones, tracks and intensity of westerly winds and competition between latitudinal and meridional types of atmospheric circulation. However the vast, some 4000 km, latitudinal expanse of the territory and eastward rise of climate continentality could have promoted existence of regional hydroclimatic differences. Analysis of west–east hydroclimate correspondence in Europe in the Holocene would contribute better understanding of changing atmospheric circulation patterns. To achieve it we compared our results from EEP to the published data on the Holocene river flooding from Great Britain, Germany and Poland derived by similar procedures (Fig. 6). For the Great Britain and Poland we used the PDFs initially obtained from regional palaeofluvial databases by Johnstone et al. (2006) and Starkel et al. (2006) and then corrected for the form of calibration curve by Macklin et al. (2006). These curves were produced from change dates and therefore they represent the occurrence of major flooding episodes in the form “event after”, i.e. peaks of PDFs are somewhat older than peaks of corresponding flooding episodes. For Germany we used the relative PDFs on activity and stability dates from Hoffmann et al. (2008). In this case both activity and stability PDFs are contemporaneous to corresponding episodes, which is similar to the PDFs from EEP. We accounted for different chronological relationships between PDFs and dated episodes when making correlations. The four regional fluvial activity curves are shown in Fig. 6 in identical timescale and positioned west to east to make spatial correlations more convenient. Two of the four regional fluvial scales contain separate indication of high and low fluvial activity (Germany), or activity and stability (EEP). In British and Polish schemes low activity/stability episodes may be deciphered indirectly as troughs of the activity curves. In the combined plot (Fig. 6), none of the high/low activity phases and only few fluvial episodes in the EEP demonstrate strict correspondence with other European regions. Probably it reflects both complex

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temporal pattern of palaeohydrological changes over Europe and differences in methods of construction of fluvial activity schemes and lack of their precision and reliability. However a number of time spans 0.2– 0.4 ka long may be identified that exhibit equal mode of fluvial activity, high or low, on two or more adjoining curves. Below we refer to central points of identified time spans rounded to 0.1 ka. All four regions, i.e. the whole Europe from west to east, demonstrate high fluvial activity at 0.8, 2.0 and 2.9 ka, and low activity at 1.2, 1.7, 6.6 and 7.9 ka b2k. Several episodes were found limited within eastern-central Europe: high activity at 5.1 and 6.3 ka, and low activity at 2.5, 4.2 and 5.6 ka b2k. High activity episode at 5.7 ka and low activity episode at 9.5 ka b2k occurred only in west-central Europe. Of the phases identified in EEP most universal for the whole Europe are the Late Holocene phases 1–3. In western and central Europe, rise of fluvial activity in the beginning of the EEP HA phase 1 started 1.1–1.2 ka b2k, some earlier than in EEP (0.9 ka b2k), and may have finished also earlier. On the graphs from Britain and Poland, fluvial activity dropped at 0.5 ka b2k, much earlier than in EEP (0.15 ka b2k). However this early drop may be due to “preferential unsampling” of young sediments in the databases for Britain and Poland. In Germany this effect is not found (Fig. 6c). LA phase 2 is the most uniform LA phase in EEP and in Germany in that it is not complicated by HA episodes, but in Germany stability phase ends earlier than in EEP – 1.2 and 0.9 ka b2k respectively. In Poland and in Britain this phase is interrupted by non-synchronous HA episodes. HA phase 3 contains two spans at 2.0 and 2.9 ka b2k which may be identified as European-wide high activity episodes. The low activity episode at 2.5 ka b2k is detected in EEP, Poland and Germany but not in Britain. Earlier in the Holocene, the European-wide palaeohydrological episodes are found only within the EEP LA phase 6. These are the two low activity episodes at 6.6 and 7.9 ka b2k. In many cases different regions demonstrate asynchronous or out of phase palaeohydrological changes. 5.5. Role of human impact in the changes of hydrological regime and fluvial activity Interpretation of increased river overbank sedimentation in central EEP in the last millennium as the result of anthropogenic impact through land use change is commonly used in Russian literature (Kurbanova, 1997; Markelov et al., 2012; Perevoschikov, 2007, etc.). Sycheva (2011) associates the increased inundation of floodplains and rise of overbank sedimentation rates with climatic conditions of Little Ice Age. However she suggests that deforestation and land cultivation and corresponding acceleration of erosion were responsible for high thickness of overbank alluvium of the last millennium and its particular features such as clear lamination and higher sand/silt ratio. In our study, both sedimentological and geomorphic traces of increased fluvial activity in the beginning of the second millennium CE (start of high activity phase 2 – 900 b2k, episode H1.2 – 600 b2k) were found over vast areas in the central and southern EEP, either populated or uninhabited (Table 2; see also the end of Section 3.2 for brief occupation history of EEP). Consistent spread of occupation area and increase of population density since the beginning of Slavonic colonization of EEP in the 9th-10th centuries were not followed by constant rise of fluvial activity but rather were accompanied by variations of both sedimentation rates and geomorphic activity (phases 1 and 1 in Table 2). These data support rather climatic than human origin of the increased overbank sedimentation in river floodplains in the last millennium. Erosion in small catchments demonstrates higher sensitivity to land use changes: in the test area in the south-west Moscow Region, increased erosion rates in old gullies are found in the last 400–50 years, which coincides with establishment of permanent settlements and rise of population density in the area (Panin et al., 2009). However,

Please cite this article as: Panin, A., Matlakhova, E., Fluvial chronology in the East European Plain over the last 20 ka and its palaeohydrological implications, Catena (2014), http://dx.doi.org/10.1016/j.catena.2014.08.016

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Fig. 6. Comparison of fluvial activity chronologies in a west–east transect across Europe: a – flooding episodes in Great Britain (Johnstone et al., 2006; Macklin et al., 2006); b – fluvial activity and stability chronologies in Germany (Hoffmann et al., 2008); c – flooding episodes in Poland (Macklin et al., 2006; Starkel et al., 2006); d – high and low fluvial activity chronologies in the East European Plain (EEP) (this study). Red and blue background (dark gray and light gray in printed version) mark EEP phases of high and low fluvial activity respectively. For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.

even stronger increase of gully erosion accompanied by appearance of new gullies occurred in the same area in several phases between 3 and 6 ka b2k when no human presence in a wide surrounding area is known (Panin et al., 2009, 2011). Two of the detected rises of gully erosion correspond to the C-episodes detected in the present study and characterized by occurrence of high-activity features rather in small than big catchments (Table 2: episode С3.2 – 3000 b2k, episode C4.2 – 4500 b2k). This may support the interpretation of these gullying phases as resulting from extreme storm activity phases (Panin et al., 2011). 6. Conclusion Collecting numerical ages of fluvial deposits, their indexing according to corresponding geomorphic or sedimentological phenomena and combining of classified dates to obtain their probability density functions provided us with proxies of high and low fluvial activity over the East European Plain. They were used to construct palaeohydrological periodization for the post-LGM time at three hierarchical levels. Two contrast palaeohydrological epochs were found: the post-LGM MIS 2 (18–11.7 ka b2k – before CE 2000) characterized by very high runoff amounts, and the Holocene with much smaller runoff amounts and lower fluvial activity compared to the Late Glacial time. Within the Holocene epoch, eight palaeohydrological phases were distinguished of relatively high (odd numbers) and low (even numbers) fluvial activity associated with changing flood magnitudes and overall runoff amounts. The oldest phase 7 bears features of fluvial system relaxation after abundant runoff in the Late Glacial. The Mid Holocene between 8.5 and 5.5 ka b2k (phase 6) was the Holocene's longest interval of low floods and small runoff amounts. After 5.5 ka b2k, oscillations of fluvial activity began with growing amplitude, mainly because of growing peaks of high fluvial activity that coincided with colder climatic phases. The last active phase 1 corresponds to Little Ice Age. Low fluvial activity coincided with warm climatic intervals: phase 2 – Medieval Climatic Optimum, the current phase 0 (since the 19th century) – the modern climatic warming.

Within the palaeohydrological phases, a total of 19 palaeofluvial episodes were detected with high (7 HA-episodes), low (8 LA-episodes) and contrast activity (4 CA-episodes). The latter were characterized by simultaneous (within the time resolution of decades to few centuries) occurrence of both high and low activity phenomena. Potential explanation of such episodes may involve: (1) separation of high and low activity over territory (not found, probably, because of insufficient amount of data), (2) short-term high-amplitude oscillations of activity within designated episodes (not investigated because of insufficient temporal resolution of data), (3) occurrence in different parts of fluvial systems – catchments of different size (probably detected for the last two CA-episodes around 3000 and 4500 b2k and explained by the predominant influence of rising storminess in the warm season while other high activity episodes seem to have been governed by rising snowmelt runoff). Comparison of the constructed hydroclimatic chronology with palaeopedological and lake level data revealed good correspondence in the second half of the Holocene and much less accordance before 4 ka b2k. This is very likely explained by insufficient amount and reliability of data behind all kinds of reconstructions. Consequently, the perspective of future research is associated with further rising of arrays of dated LPEs, particularly that from the Early and Mid Holocene. Correlation of fluvial activity changes throughout the west-central to eastcentral Europe revealed relatively poor similarity in the Early and Mid Holocene, with the highest resemblance between 6.5 and 8 ka b2k when two European-wide time spans of low fluvial activity/stability were found. Since 3.0 ka b2k palaeohydrological changes demonstrate significantly higher synchronism throughout Europe, which may mean rising climatic role of westerlies and their deeper penetration into the continental interior in the Late Holocene. Analysis of the role of anthropogenic factor in regional palaeohydrological changes over EEP showed that throughout the whole Holocene, dynamics of fluvial activity was governed by natural climate forcing until the last few centuries when land use changes induced accelerated hillslope and gully erosion.

Please cite this article as: Panin, A., Matlakhova, E., Fluvial chronology in the East European Plain over the last 20 ka and its palaeohydrological implications, Catena (2014), http://dx.doi.org/10.1016/j.catena.2014.08.016

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Acknowledgment Financial support for this study was received from the Russian Foundation for Basic Research (RFBR), Project No. 14-05-00146.

References Alexandrovskiy, A.L., Alexandrovskaya, E.I., 2005. Evolucia pochv i geograficheskaya sreda (Soil evolution and the geographical environment). Nauka Publ., Moscow (223 pp., in Russian). Alexandrovskiy, A.L., Krenke, N.A., 2004. Stages of soil formation on floodplains in the centre of the Russian Plain. In: Dobrzanska, H., Jerem, E., Kalicki, T. (Eds.), The Geoarchaeology of River Valleys. Archaeolingua, Budapest, pp. 171–184. Arpe, K., Leroy, S.A.G., 2007. The Caspian Sea level forced by the atmospheric circulation, as observed and modeled. Quat. Int. 173–174, 144–152. Belyaev, V.R., Golosov, V.N., Markelov, M.V., Evrard, O., Ivanova, N.N., Paramonova, T.A., Shamshurina, E.N., 2013. Using Chernobyl-derived 137Cs to document recent sediment deposition rates on the River Plava floodplain (Central European Russia). Hydrol. Proced. 27 (6), 807–821. Bessudnov, A.N., Zaretskay, N.E., Pokrovskiy, B.G., Kuznetsova, T.V., Panin, A.V., Bessudnov, A.A., Burova, N.D., 2013. Osobennosti i chronologia formirovaniya tafocenoza loshadei v Divnogorye, bassein Srednego Dona (Specific features and chronology of the horsebone tafocenosis at Divnodorye, the Middle Don River basin). VIII Vserossiyskoye soveschanie po izecheniu chenvertichnogo perioda. YNC RAN, Rostov, pp. 70–72 (in Russian). Borisova, O., Sidorchuk, A., Panin, A., 2006. Palaeohydrology of the Seim River basin, MidRussian Upland, based on palaeochannel morphology and palynological data. Catena 66, 53–73. Bronk Ramsey, C., 2009. Bayesian analysis of radiocarbon dates. Radiocarbon 51 (1), 337–360. Chiverrell, R.C., Thorndycraft, V.R., Hoffmann, T.O., 2011. Cumulative probability functions and their role in evaluating the chronology of geomorphological events during the Holocene. J. Quat. Sci. 26, 76–85. Dolukhanov, P.M., Subetto, D.A., Arslanov, K., Davydova, N.N., Zaitseva, G.I., Kuznetsov, D.D., Ludikova, A.V., Sapelko, T.V., Savelieva, L.A., 2010. Holocene oscillations of the Baltic Sea and Lake Ladoga levels and early human movements. Quat. Int. 220 (1–2), 102–111. Efimova, N.A., 1987. Izmenenia usloviy uvlazhnenia na chasti territorii Evrasii pro vozmozhnom global'nom poteplenii climata (Change of humidity over a part of Eurasia as a result of possible global warming). Meteorol. Gidrol. 11, 54–58 (in Russian). Golosov, V.N., 2009. Issledovania akkumulacii nanosov na poimakh rek: potencial'nie metody I perspektivy (Investigations of sediment deposition on the floodplains: potentials of methods and perspectives). Geomorfologiya 4, 39–45 (in Russian). Hoffmann, T., Lang, A., Dikau, R., 2008. Holocene river activity: analysing 14C-dated fluvial and colluvial sediments from Germany. Quat. Sci. Rev. 27, 2031–2040. Johnstone, E.C., Macklin, M.G., Lewin, J., 2006. The development and application of a database of radiocarbon-dated Holocene fluvial deposits in Great Britain. Catena 66, 14–23. Karmanov, V.N., Chernov, A.V., Zaretskaya, N.E., Panin, A.V., Volokitin, A.V., 2013. Paleochannel studies in archaeology: the case of the Vychegda River, Northeastern European Russia. Archaeol. Ethnol. Anthropol. Eurasia 41 (2), 83–93. Karpytchev, Yu.A., 1993. Reconstruction of Caspian Sea-level fluctuations: radiocarbon dating coastal and bottom deposits. Radiocarbon 35 (3), 409–420. Khotinskiy, N.A., 1989. Diskussionnye problemy reconstrukcii i correlacii paleoclimatov golocena (Controversies in reconstructions and correlations of the Holocene palaeoclimates). Paleoklimaty Pozdnelednikovia i Golocena. (Palaeoclimates of the Late Glacial and the Holocene). Nauka Publ., Moscow, pp. 12–17 (in Russian). Kroonenberg, S.B., Abdurakhmanov, G.M., Badyukova, E.N., van der Borg, K., Kalshnikov, A., Kasimov, N.S., Rychagov, G.I., Svitoch, A.A., Vonhof, H.B., Wesselingh, F.P., 2007. Solarforced 2600 BP and Little Ice Age highstands of the Caspian Sea. Quat. Int. 173–174, 137–143. Kroonenberg, S.B., Kasimov, N.S., Lychagin, M.Yu., 2008. The Caspian Sea: a natural laboratory for sea-level change. Geogr. Environ. Sustain. 1, 22–37. Kurbanova, S.G., 1997. Antropogennoye izmenenie rezhima stoka i erozionnoakkumuliativnykh processov v Srednem Povolzhie (Anthropogenic transformation of runoff regime and erosion/sedimentation processes in the Middle Volga Region). PhD Thesis Kazan University, (153 pp., in Russian). Lang, A., 2003. Phases of soil erosion-derived colluviation in the loess hills of South Germany. Catena 51, 209–221. Leroy, S.A.G., Marret, F., Gibert, E., Chalié, F., Reyss, J.-L., Arpe, K., 2007. River inflow and salinity changes in the Caspian Sea during the last 5500 years. Quat. Sci. Rev. 26 (25), 3359–3383. Macklin, M.G., Lewin, J., 1993. Holocene river alluviation in Britain. Z. Geomorphol. Suppl. 88, 109–122. Macklin, M.G., Lewin, J., 2003. River sediments, great floods and centennial-scale Holocene climate change. J. Quat. Sci. 18 (2), 101–105. Macklin, M.G., Johnstone, E., Lewin, J., 2005. Pervasive and long-term forcing of Holocene river instability and flooding in Great Britain by centennial-scale climate change. Holocene 15 (7), 937–943. Macklin, M.G., Benito, G., Gregory, K.J., Johnstone, E., Lewin, J., Michczynska, D.J., Soja, R., Starkel, L., Thorndycraft, V.R., 2006. Past hydrological events reflected in the Holocene fluvial record of Europe. Catena 66, 145–154.

15

Macklin, M.G., Jones, A.F., Lewin, J., 2011. Comment: Cumulative probability functions and their role in evaluating the chronology of geomorphological events during the Holocene. Richard C. Chiverrell, Varyl R. Thorndycraft and Thomas O. Hoffmann, Journal of Quaternary Science 26, 76–85. J. Quat. Sci. 26, 238–240. Macklin, M.G., Fuller, I.C., Jones, A.F., Bebbington, M., 2012. New Zealand and UK Holocene flooding demonstrates interhemispheric climate asynchrony. Geology 40 (9), 775–778. Markelov, M.V., Golosov, V.N., Belyaev, V.N., 2012. Izmenenia tempov accumulatcii nanosov na poimakh malykh rek v centre Russloy ravniny (Changing sedimentation rates in small river floodplains in the Centre of Russian Plain). Vestn. Mosk. Univ. Ser. 5 Geogr. 5, 70–76 (in Russian). Michczynska, D.J., Pazdur, A., 2004. Shape analysis of cumulative probability density function of radiocarbon dates set in the study of climate change in Late Glacial and Holocene. Radiocarbon 46 (2), 733–744. Michczynska, D.J., Michczynski, A., Pazdur, A., Zurek, S., 2003. 14C dates of peat for reconstruction of environmental changes in the past. Geochronometria 22, 47–54. Michczynski, A., Michczynska, D.J., 2006. The effect of PDF peaks' height increase during calibration of radiocarbon date sets. Geochronometria 25, 1–4. Mikhailov, V.N., Povalishnikova, E.S., 1998. Esche raz o prichinakh izmeneniy urivnya Caspiiskogo morya v XX veke (Once more on the reasons of the Caspian Sea level changes in the XX century). Vestn. Mosk. Univ. Ser. 5 Geogr. 3, 35–38 (in Russian). Naderi Beni, A., Lahijani, H., Mousavi Harami, R., Arpe, K., Leroy, S.A.G., Marriner, N., Berberian, M., Andrieu-Ponel, V., Djamali, M., Mahboubi, A., Reimer, P.J., 2013. Caspian Sea-level changes during the last millennium: historical and geological evidence from the south Caspian Sea. Clim. Past 9, 1645–1665. Panin, A.V., Sidorchuk, A.Ju., Chernov, A.V., 1999. Historical background to floodplain morphology: examples from the East European Plain. In: Marriott, S., Alexander, J., Hey, R. (Eds.), Floodplains: Interdisciplinary Approaches. Geol. Soc., London, Spec. Publ. 163, pp. 217–229 Panin, A.V., Fuzeina, J.N., Belyaev, V.R., 2009. Long-term development of Holocene and Pleistocene gullies in the Protva River basin, Central Russia. Geomorphology 108, 71–91. Panin, A., Fuzeina, Yu., Karevskaya, I., Sheremetskaya, E., 2011. Mid-Holocene gullying indicating extreme hydroclimatic events in the centre of the Russian Plain. Geogr. Pol. 84 (Spec. Iss. Part 1), 95–115. Panin, A.V., Sidorchuk, A.Yu., Vlasov, M.V., 2013. Moschniy pozdnevaldaiskiy rechnoy stok v basseine Dona (Abundant river runoff in the Don River Basin in the Late Pleniglacial). Izv. RAN Ser. Geogr. 1, 118–129 (in Russian). Panin, A.V., Adamiec, G., Arslanov, Kh.A., Bronnikova, M.A., Filippov, V.V., Sheremetskaya, E. D., Zaretskaya, N.E., Zazovskaya, E.P., 2014. Absolute chronology of fluvial events in the Upper Dnieper river system and its palaeogeographic implications. Geochronometria 41 (3), 278–293. Pavlov, P., Svendsen, J.I., Indrelid, S., 2001. Human presence in the European Arctic nearly 40,000 years ago. Nature 143, 64–67. Perevoschikov, A.A., 2007. Voprosy proiskhozhdenia i diagnosticheskie priznaki antropogenno obuslovlennogo poimennogo alluvia (Origin and diagnostic characteristics of anthropogenically stimulated overbank alluvium sedimentation). Vestn. Udmurt. Univ. Nauki Zemle 11, 111–121 (in Russian). Peros, M.C., Munoz, S.E., Gajewski, K., Viau, A.E., 2010. Prehistoric demography of North America inferred from radiocarbon data. J. Archaeol. Sci. 37, 656–664. Rasmussen, S.O., Andersen, K.K., Svensson, A.M., Steffensen, J.P., Vinther, B.M., Clausen, H.B., Siggaard-Andersen, M.L., Johnsen, S.J., Larsen, L.B., Bigler, M., Röthlisberger, R., Fischer, H., Goto-Azuma, K., Hansson, M.E., Ruth, U., 2006. A new Greenland ice core chronology for the last glacial termination. J. Geophys. Res. 111, D06102. Reimer, P.J., Bard, E., Bayliss, A., Beck, J.W., Blackwell, P.G., Bronk Ramsey, C., Buck, C.E., Cheng, H., Edwards, R.L., Friedrich, M., Grootes, P.M., Guilderson, T.P., Haflidason, H., Hajdas, I., Hatté, C., Heaton, T.J., Hoffmann, D.L., Hughen, K.A., Kaiser, K.F., Kromer, B., Manning, S.W., Niu, M., Reimer, R.W., Richards, D.A., Scott, E.M., Southon, J.R., Staff, R.A., Turney, C.S.M., van der Plicht, J., Hogg, A., 2013. IntCal13 and Marine13 radiocarbon age calibration curves 0–50,000 years cal BP. Radiocarbon 55 (4), 1869–1887. Rychagov, G.I., 1997a. Holocene oscillations of the Caspian Sea, and forecasts based on palaeogeographical reconstructions. Quat. Int. 41/42, 167–172. Rychagov, G.I., 1997b. Pleistocenovaya Istoria Caspiiskogo Morya (Pleistocene History of the Caspian Sea). Moscow Univ. Publ., (267 pp.). Sheetov, M.V., Biske, Yu.S., Pleshivtseva, E.S., Marakov, A.Ya., 2005. Pozdnegolocenovye izmeneniya urovnya Volkhova v rayone Staroy Ladogi (The Volkhov River level changes in the Late Holocene at Staraya Ladoga town). Vestn. Sankt-Pereburgskogo Univ. Ser. 7 4, 3–16 (in Russian). Sidorchuk, A., Panin, A., Borisova, O., 2009. Morphology of river channels and surface runoff in the Volga River basin (East European Plain) during the Late Glacial period. Geomorphology 113, 137–157. Sidorchuk, A., Panin, A., Borisova, O., 2011. Surface runoff to the Black Sea from the East European Plain during Last Glacial Maximum–Late Glacial time. In: Buynevich, I., Yanko-Hombach, V., Gilbert, A.S., Martin, R.E. (Eds.), Geology and Geoarchaeology of the Black Sea Region: Beyond the Flood Hypothesis. Geol. Soc. Am. Spec. Pap. 473, pp. 1–25 Starkel, L., Soja, R., Michczynska, D.J., 2006. Past hydrological events reflected in Holocene history of Polish rivers. Catena 66, 24–33. Sulerzhitskiy, L.D., 2004. Vremya suschestvovatiya nekotorykh pozdnepaleoliticheskikh poseleniy po dannym radiouglerodnogo datirovaniya kostei megafauny (Age of selected Late Palaeolithic sites according to radiocarbon dating of megafauna bones). Ross. Archeol. 3, 103–112 (in Russian). Sycheva, S.A., 2006. Long-term pedolithogenic rhythms in the Holocene. Quat. Int. 152–153, 181–191. Sycheva, S.A., 2011. Maliy climaticheskiy optimum golocena I maliy lednikoviy period v pamyati pochv i otlozheniy poim rek Russkoi ravniny (Little Climatic Optimum and

Please cite this article as: Panin, A., Matlakhova, E., Fluvial chronology in the East European Plain over the last 20 ka and its palaeohydrological implications, Catena (2014), http://dx.doi.org/10.1016/j.catena.2014.08.016

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A. Panin, E. Matlakhova / Catena xxx (2014) xxx–xxx

Little Ice Age recorded in soils and sediments in river floodplains in the Russian Plain). Izv. RAN Ser. Geogr. 1, 79–93 (in Russian). Tarasov, P.E., Gunova, V.S., Uspenskaya, O.N., 1997. Urovni ozer basseina Volgi kak indicator izmenenia climata v golocene (Lake levels in the Volga River catchment as indicators of Holocene climate changes). Vestn. Mosk. Univ. Ser. 5 Geogr. 3, 36–41 (in Russian). Thorndycraft, V.R., Benito, G., 2006. The Holocene fluvial chronology of Spain: evidence from a newly compiled radiocarbon database. Quat. Sci. Rev. 25, 223–234. Velichko, A.A., Klimanov, Belyaev, A.V., 1988. Reconstrukcia stoka Volgi I vodnogo balansa Caspia v opyimumy mikulinskogo mezhlednokovia i golocena (Assessment of the Caspian Sea water balance during the optimal phases of the Eemian and the Holocene). Izv. Akad. Nauk SSSR 1, 27–37 (in Russian). Vinnikov, K.Ya., Lemeshko, N.A., 1987. Vlagosoderzhanie pochvy i stok dlya territotii SSSR pri global'nom poteplenii (Soil humidity and runoff over the USSR under the global warming). Meteorol. Gidrol. 12, 96–103 (in Russian).

Walker, M., Johnsen, S., Rasmussen, S.O., Popp, T., Steffensen, J.P., Gibbard, P., Hoek, W., Lowe, J., Andrews, J., Bjorck, S., Cwynar, L.C., Hughen, K., Kershaw, P., Kromer, B., Litt, T., Lowe, D.J., Nakagawa, T., Newnham, R., Schwander, J., 2009. Formal definition and dating of the GSSP (Global Stratotype Section and Point) for the base of the Holocene using the Greenland NGRIP ice core, and selected auxiliary records. J. Quat. Sci. 24, 3–17. Williams, A.N., 2012. The use of summed radiocarbon probability distributions in archaeology: a review of methods. J. Archaeol. Sci. 39, 578–589. Zielhofer, C., Faust, D., 2008. Mid- and Late Holocene fluvial chronology of Tunisia. Quat. Sci. Rev. 27, 580–588. Zielhofer, C., Faust, D., Linstadter, J., 2008. Late Pleistocene and Holocene alluvial archives in the Southwestern Mediterranean: changes in fluvial dynamics and past human response. Quat. Int. 181, 39–54.

Please cite this article as: Panin, A., Matlakhova, E., Fluvial chronology in the East European Plain over the last 20 ka and its palaeohydrological implications, Catena (2014), http://dx.doi.org/10.1016/j.catena.2014.08.016