I acknowledge Prof. Natalia Gerasimenko for helpful comments and correction the English. I am also grateful to Andrii Bonchkovskyi and Vladyslav Vasyliuk for participation in the field work. Many thanks to Bogdan Ridush, Larysa Kulakovska, Vitalyi Usik and Andrii Bardetskyi for their help in interpreting archaeological artefacts.

1 - Introduction

1In the Volyn’ Upland (NW Ukraine), the loess-palaeosol cover (up to 10-20 m thick) is almost continuous (with the exception of some areas of strong Neotectonic uplift such as the Povcha Upland and Mizoch Ridge. As compared with the other regions of Ukraine, loess-palaeosol units here are strongly deformed by ice-wedge casts, solifluction, and gleying processes. These features of the Volyn’ Upland loess-palaeosol cover, which obviously appeared as the result of a higher humidity, hamper correlation with stratigraphic sections in central and southern Ukraine. More intense Neotectonic uplift in the Volyn’ Upland, than in other areas of Ukraine, made very infrequent the occurrence of Lower Pleistocene and Middle Pleistocene deposits.

2The loess-palaeosol formation of the Volyn’ Upland has been intensively studied by Ukrainian, Russian and Polish researchers (e.g. Bogucki et al., 1975, 2014; Tsatskin, 1980; Morozova, 1981; Artiushenko et al., 1982; Nechaev, 1983; Bogucki, 1986; Voloshyn, 1987; Dmytruk, 2001; Bezusko & Bogucki, 2004; Jary, 2009; Bezusko et al., 2011; Bogucki & Voloshyn, 2011, 2014; Palamarchuk, 2011; Bezusko, 2013; Kusiak et al., 2012; Jary & Ciszek, 2013, Bonchkovskyi, 2015, 2019; Hlavatskyi et al., 2016). Despite the numerous studies, some problems have not been yet resolved, e.g. short environmental development phases have not been reconstructed. This was due to the concentration of the former studies on plateaux sections, whereas the most complete loess-palaeosol record are located lower in the relief, in ‘sediment traps’ (Kukla & Cilek, 1996; Gerasimenko, 2004; Sycheva, 2008). The complete loess-palaeosol sequence on the palaeoslopes or in ‘sediment traps’ has recently been studied in different regions of Europe (Antoine et al., 1999, 2009, 2013; Rousseau et al., 2001; Haesaerts et al., 2003, 2016, 2019; Gerasimenko, 2004, 2006; Łacka et al., 2007; Łanczont & Boguckyj, 2007; Moine et al., 2008; Fuchs et al., 2012; Schirmer, 2012; Gocke et al., 2014; Łanczont et al., 2015; Hošek et al., 2017; Sycheva et al., 2017, 2020; Coutard et al., 2018). As several Paleolithic sites have been discovered in the Volyn’ Upland in recent decades (Piasetskyi, 2009), reconstruction of the environment of prehistoric settlements and the relationships with human adaptation and subsistence strategies has become another important task.

2 - Site settings

3The Novyi Tik section (50°29’50’’ N, 25°12’17’’ E, 206 m a.s.l. in its highest part) is situated in the central part of the Volyn’ Upland, about 27 km south of the city of Lutsk, in the brickpit of Novyi Tik village (figs. 1 & 2). The excavations are in the left-bank slope of the Berestova River valley, a left-bank tributary of the Styr River – the main river of the area (Dnieper basin).

4In the Volyn’ Upland, the Precambrian basement, lying at a depth of 3-5 km (Gerenchuk, 1976), is overlaid by Cambrian, Silurian, Devonian and Cretaceous deposits. The Upper Cretaceous limestones, chalk and marls (with flint nodules), are up to 1000-m-thick and underlie the Quaternary loess-palaeosol formations (Bogucki et al., 2007a). The Volyn’ Upland (200-250 m a.s.l.) is intensively dissected, down to 50 m, by small river courses and gullies. Within the Povcha Upland and Mizoch Ridge, absolute elevations are higher, reaching 340-350 m. Holocene ravines are most common within the latter areas. Karst forms are seen there and developed on chalk and other limestones.

5In the Styr valley, a Middle Pleistocene and two Upper Pleistocene terraces have been distinguished (Chervanev, 1968; Gnatiuk & Novak, 2016). At places, the younger terrace alluvium is superimposed on the older one. Sand dunes (up to 4-5 m in height) are located on the youngest (Late Pleniglacial) terrace. The larger tributaries of the River Styr within the Volyn’ Upland are the Ikva, Lypa and Chornoguska rivers. The last two during the Oka (Elsterian) glaciation carried glacial melt water (Bogucki, 1969). The Novyi Tik site is located on a valley slope near the head of the Berestova River. Two fragmented terraces of this river can be distiguished near its mouth, where they gradually join the terraces of the River Styr.

6The climate of the area is now temperate, less continental than in the central and eastern Ukraine. The mean annual temperature is +7.9°С, the mean January temperature is -3.5°С, and the mean July temperature +19.0°С. Mean annual precipitation is 570 mm (mainly summer precipitation). Westerly and north-westerly winds dominate.

7In the Volyn’ Upland, Greyzemic Phaeozem, Luvic Phaeozem, Luvic Chernozem, and Chernic Chernozem are common. On the sandy river terraces, Retisol and Arenosol occur. Leptosol forms on the marl and chalk/limestones outcrops (Pozniak et al., 2019). The modern vegetation comprises agrocoenoses. The natural vegetation, locally preserved, consists of oak-hornbeam woods on loess plateaux and meadow steppe on the slopes of gullies and valleys. On low alluvial terraces, pine, pine-birch and mixed (pine-hornbeam-oak) woodland occurs (Gerenchuk, 1976; Kuzmishyna, 2008).

3 - Materials and methods

8From 2014 to 2020, the site’s stratigraphy has been studied in 16 outcrops (figs. 3 & 4). The Pleistocene buried gullies were revealed in the quarry exposures. Twenty-one basic stratigraphic units have been revealed, some of which are polygenetic soils, therefore, they are divided into subunits (e.g. subunits 18a and 18b).

9Grain-size has been measured by the pipette technique of Kachynskyi (Kachynskyi, 1958), recording the following fractions: < 1 µm (clay), 1-5 µm (very fine silt), 5-10 µm (fine silt), 10-50 µm (coarse silt or ‘loess fraction’), 50-250 µm (fine sand) and > 250 µm (coarse sand). Humus content was determined using Turin’s method (Arinushkina, 1970). The micromorphology of loess and palaeosol units has been studied according to the methodology of Parfeneva & Yarilova, 1977; Matviishyna, 1982; Gerasimova et al., 1992; Stoops et al., 2003; Gagarina, 2004. A study of the micromorphology of the soils of unit 10, formed on different parent rocks, has been carried out (sections #2, 6 and 12) (fig. 3). The classification of palaeosols follows IUSS Working Group WRB (2015), whereas the features of their genetic horizons (pedons) have been described according to FAO (2006).

10Pollen data have been obtained from all genetic horizons of palaeosols and from some loess units (units 7 and 17) in sections #1, 2, 6, 11 (fig. 3). Pollen samples have been prepared using the following techniques: boiling in a 10 % HCl solution to remove carbonates; boiling in a Na⁴P²O⁷ solution to remove clay particles; boiling in HCl to remove secondary carbonates; boiling in a 10 % KOH solution to remove organic matter; separation in a heavy liquid (CdI2+KI) with the specific gravity 2.0-2.2, and, finally, treatment with a 40 % HF solution to remove quartz grains. In the pollen diagrams, all percentages have been calculated from the total sum of pollen and spores. The correlation between grain-size and content of palynomorphs have been noted. Pollen and spores frequencies are lower in beds with a high content of sand and, thus, within well-aerated sediments. The majority of palynomorphs was well-preserved and identifiable. When reconstructing palaeovegetation from pollen data, the over-representation of Pinus pollen has been taken into account, as well as under-representation of pollen of broad-leaved trees and grasses. The transfer functions of Grychuk (1989) and Bolikhovskaya (1995) have been used in this respect.

4 - Results

4.1 - Studied sections

11Site’s stratigraphy has been studied in 16 outcrops, located in the different forms of palaeorelief (figs. 3 & 4). The welded palaeosols of plateaux turn into well-developed pedocomplexes including thin loess beds in palaeogullies, and in some places into facies of pedosediments. Well-developed palaeosol complexes are also exposed on the slopes of the river valley. The correlation between different sections is reliable due to the large number of sections that makes it possible to trace easily the lateral variability of each unit from one profile to another. If there were any doubts in correlation between adjacent sections, then additional sections have been excavated ad cleaned in between.

12In the Novyi Tik sequence, six main subdivisions (three pedocomplexes and three main loess series) have been distinguished and subdivided into 21 units (fig. 3). The lowest units (20-21) were excavated at the bottom of the quarry, though the bedrock (Createceous limestones) was not found.

13The synthetic macromorphological and micro-morphological descriptions of the main stratigraphic units can be seen in table 1 and the summary of micromorphological features of site palaeosols is given in table 2.

4.2 - Stratigraphy

4.2.1 - Pedocomplex III

14The soil complex is related to unit 20 that is underlaid by the loess-like silt (unit 21). The lastest is characterised by a high content of the ‘loess fraction’ (52.3 %) (fig. 5). It was significantly modified by both illuviation processes and bioturbation linked with the subsequent pedogenesis that led to the formation of unit 20.

15Two different soils (subunits 20a and 20b) are distinguished within the Pedocomplex III (fig. 6F) owing to presence of a network of up to 1.0‑1‑2‑m-deep soil veins and frost fissures that open from the top of the Eg horizon of the lower soil. Although each of the soils is made of a Bt horizon, their pollen assemblages differ. The lower soil (subunit 20b) is the Luvisol with horizons Eg, Bt, Btg and BCtg. The fine organic matter is present only in the upper horizon Eg, whereas the prevalence of clay coatings (fig. 7L) sharply increases downward (in Bt, Btg and BCtg horizons). Cutans include both streaks of fine organic matter and individual dust grains. The latter indicates a very active lessivage (Bronnikova, 2008). The lower part of the Luvisol is disturbed by crotovinas filled in with material from the upper soil.

16In the lower soil (subunit 20b), three pollen assemblages have been obtained, the two upper of them are of a forest type (fig. 8). Pollen of Pinus sylvestris L. (44.3 %) dominates in the Eg horizon, though broad-leaved trees Quercus sp., Ulmus sp. and Corylus avellana L., as well as Picea abies (L.) Karst. are also well represented. The pollen from the Btg horizon is dominated by Pinus sylvestris L. (55.9 %), broad-leaved species being absent. Spores of ferns (Filicales, trilete and monolete) and club-mosses (Lycopodiaceae) frequently occur. In the BCtg horizon, NAP significantly increases, especially Poaceae (33.3 %), whereas pollen of Pinus sylvestris L. decreases (19 %). Palynomorphs of Picea abies (L.) Karst. (4.8 %) and Ephedra distachya L. (4.8 %) appear.

17The upper soil (subunit 20a) is secondary gleyed and deformed by solifluction, reticulate-blocky post-cryogenic textures and soil veins up to 1.5-m deep that open from the top of the subunit. The soil includes Ag and Btg horizons. The content of clay increases to 23.9 % downward and microlaminated clay coatings appeared there. The dusty grains are concentrated along fissures that probably result from cryogenic sorting, by analogy with the modern tundra soils formed under multiple freeze-thawing cycles (Rogov, 1989).

18The pollen assemblage of the upper soil (subunit 20a) is of forest-steppe type (fig. 8). Pinus sylvestris L. (25.5 %), Alnus sp. (10.9 %) and Betula sp. (5.5 %) dominate in the AP, whereas NAP is mainly that of ruderal plants: Asteraceae (10.9 %) and Lactuceae (14.5 %). Pollen of xerophytic herbs (Ephedra distachya L. and Chenopodiaceae) occur in very low percentages.

4.2.2 - Loess III

19The loess (unit 19) is weakly gleyed, has a high content of coarse silt (55.5 %) (fig. 5) and large carbonate nodules (up to 5 cm large). In the lower part of the loess, the Bk horizon of the Pedocomplex II is located. The 0.3-m-thick lower part of the unit is disturbed by solifluction.

4.2.3 - Pedocomplex II

20The soil complex comprises two welded soils (units 16-18) separated by loess-like silt (unit 17) (fig. 6e). The unit 18 is likely represented by two soils (subunits 18a and 18b), as evidenced by clearly different pedological features and pollen assemblages. On the palaeoslopes (sections #9-11), the upper soil is almost truncated (fig. 3). The lower soil (subunit 18b) has Eg and Bt horizons. In the Bt horizon, there are well-expressed prismatic structure and microlaminated clay coatings that enable to interpret it as a Luvisol. The upper part of the soil has carbonate nodules associated with the later pedogenesis. In the palaeogully (section #2) (fig. 3), carbonate nodules occur along the entire profile.

21In the lower soil (subunit 18b), two different pollen spectra have been revealed (fig. 8). In the Eg horizon, spores prevail, and pollen of Alnus sp. (7.7 %) and Betula sp. (3.8 %) occur. The percentages of Cyperaceae are high (19.2 %). In the Bt horizon, the assemblage is of forest type: arboreal pollen (AP) is strongly dominated by Tilia cordata Mill. (71.8 %), with only a few grains of Pinus sylvestris L. and Alnus sp. Percentages of Cyperaceae (6.4 %) and Ephedra distachya L. (3.6 %) are low.

22The upper soil (subunit 18a) is richer in humus, with considerable fine organic material and granular microaggregates in thin sections, though microlaminated clay coatings also present. This soil is interpreted as an incipient Luvic Phaeozem. The pollen assemblage of the soil is of forest-steppe type (fig. 8). The AP includes Pinus sylvestris L. (23.4 %), Alnus sp. (4.2 %) and a few pollen of Salix sp., and Pinus cembra L. Pollen of broad-leaved species is absent, whereas pollen of xerophytes, Chenopodiaceae (11.3 %) and Ephedra distachya L. (1.4 %) occur.

23The loess bed (unit 17) in the middle of the Pedocomplex II is weakly gleyed and enriched in ‘loess frac tion’ (59.5 %) (fig. 5). Small frost fissures up to 0.5 m deep open from the middle of the unit and they are filled with the loess material. The pollen assemblages of this unit are of tundra-steppe type and includes Betula sect. Nanae (2.2-7.8 %) and Ephedra distachya L. (6.7-7.8 %). In the upper part of the loess, Lycopodiaceae spores are most abundant (41.2 %). In its lower part, pollen of Pinus sylvestris L. (20 %) and arboreal birch (2.2 %) occurs.

24The unit 16 evidently comprises two steppe soils (16a and 16b), in places (section #11), separated by a thin loess layer (fig. 3). Soil wedges and veins up to 1-2 m deep dissect the unit. In section #1, soil veins of two separate cryogenic events are well distinguished. The oldest cryogenic features are represented by soil wedges and veins opening from the top of the lower soil (subunit 16b), whereas the youngest ones are thinner but deeper soil veins opening from the top of the upper soil (subunit 16a). In other sections where subunit 16a is truncated, it is very difficult to separate both generations of wedges and veins.

25The lower soil, interpreted as a Chernozem, includes А, АВ and BC horizons. The soil is enriched in coarse silt (64 %) (fig. 5). A lot of bioturbation affects the lower part of the soil and the subsoil. Few clay coatings occur in the upper part of the soil presumably as the result of later pedogenesis. The pollen assemblage of the subunit 16b is dominated by non-arboreal pollen (NAP) (from 42.1 % in the AB horizon to 52.2 % in the A horizon), especially forbs (43-53 %) (fig. 8). In the A horizon, pollen of broad-leaved taxa (mainly Quercus sp., Ulmus sp. and Corylus avellana L.) increase (from 1.6 % to 4.4 %), as well as pollen of xerophytes (mainly Ephedra distachia L.) and hygrophytes (Cyperaceae). In the AB horizon, Carpinus betulus L., Quercus sp., Ericaceae and Juniperus sp. occur.

26The upper soil (subunit 16a) is mainly disturbed by solifluction and, in places, involutions. On the palaeoslopes, this unit is entirely eroded (sections #2, 6-8), or it is truncated (fig. 3). The soil is enriched in coarse silt (60 %) and, relatively, in humus (0.49 %) (fig. 5). In the lower part of the soil, the appearance of clay coatings enables identification of a BCt horizon. In the upper part of the soil, spongy microstructure with the pronounced biogenic aggregates is present (fig. 7H). Moreover, there is a platy microstructure, which according to Rode & Smirnov (1972) and Antoine et al. (1999), resulted from segregation of ice lenses. On the basis of these features, the soil is interpreted as a Cambisol.

27The pollen assemblage of subunit 16a is of mesophytic steppe type (fig. 8). Pollen of forbs dominates: mainly Asteraceae (13.1 %) and Lactuceae (11.2 %). They share dominance with Cyperaceae (20.6 %), and the xerophyte Ephedra distachya L. is noteworthy (14 %). The AP consists of a few grains of Corylus avellana L., Alnus sp., Pinus sylvestris L. and P. cembra L.

4.2.4 - Loess II

28The unit 15 is mainly represented by a loess-like silt (‘loess fraction’ 72 %) (fig. 5), penetrated by reticulate and reticulate-blocky post-cryogenic textures (1-2 cm by 2-4 cm). In thin sections, the groundmass is broken by a system of perpendicular fissures and planes, defining angular blocks. The reticulate pattern of the pore space, according to Van Vliet-Lanoё (1998), has a cryogenic genesis.

29Towards the river valley, the whole unit is disturbed by solifluction, and re-deposited flints (up to 5 cm in diameter) appear here. On the gentle slopes (2-3° steep), the lower part of the loess is deformed by solifluction, whereas on palaeoslopes with an angle of 5°, solifluction is completely replaced by hillwash textures. The lower part of the unit includes a level with gleying (subunit 15b) (fig. 3).

30Frost fissures up to 0.7-m-deep, filled with ferrous-rich sandy silt, open from the top of the unit. As the result of involutions, that disturb the upper part of loess, cryostructures have intricate shapes. The disturbed zone is only 20-30 cm thick. From the middle part of the unit, a 1.5-m‑deep ice‑wedge pseudomorph, partially eroded, opens. The structure is filled with loess, which is absent above in the section (fig. 9e). Subsidence textures occur in the loess. According to Van Vliet-Lanoё et al. (2016), they could appear as the result of reticulate ice melting.

4.2.5 - Pedocomplex I

31The structure of the pedocomplex is dependent on the palaeorelief. On the palaeoplateaux (section #1), the unit comprises only two soils: the upper Chernozem and the lower Podzol (fig. 3). The latter is disturbed by involutions (fig. 9d) and soil veins. In the palaeogullies (sections #2, 12), these soils are replaced by a well-developed pedocomplex (fig. 3). The lower forest soil and bedded pedosediments of the forest soils (sections #8-12) appear clearly correlated. The facies change from the Podzol soil on the plateau to the Stagnic Retisol (unit 13) in the palaeogully (section #2-3) can be traced visually (fig. 6b). Towards the river (sections #5-6), the two soils (subunits 12a and 12b) appear above pedosediments of the Retisol (unit 13) (fig. 6d), whereas in the section #11, the Gleysol (unit 14) appears under these pedosediments.

32The Stagnic Retisol (unit 13) includes A, BEg and Bt horizons. The top of the unit is truncated by a sharp erosional boundary. The humified A horizon has a well-expressed prismatic structure, with cutans on the ped surfaces, which is not typical for A horizons. Thus, it may be assumed that after formation of the A horizon, it was re-worked by translocation processes from the overlying soil. The A horizon of this soil was obviously truncated later. Downslope, the Stagnic Retisol is replaced by pedosediments.

33The pollen assemblage of the unit 13 is dominated by AP (fig. 8), including Pinus sylvestris L. (12.1 %), Carpinus betulus L. (5.2 %), Ulmus sp. (3.4 %), Betula sp. (4.3 %) and rare Quercus sp., Picea abies (L.) Karst. and Alnus sp. Spores of ferns and mosses occur frequently.

34The Gleysol (unit 14) in the section #11 is characterised by the prismatic structure and cutans on the ped surfaces that indicate an illuviation processes, presumably, of a subsequent pedogenesis. The pollen assemblage of unit 14 is dominated by Betula sp. (23.1 %) and Cyperaceae (32.3 %) (fig. 8). Spores of ferns, club-mosses and green mosses are also abundant, including Sphagnum sp.

35Towards the river (sections #5-6), two soils (subunits 12a and 12b) appear above the pedosediments of the Retisol (unit 13) (fig. 6d). The lower soil (subunit 12b) includes Eg and Bt horizons. Locally, a thin soil horizon A, is observed. The well-developed prismatic structure as well as microlaminated clay coatings occur in the Bt horizon (fig. 7G). In the Eg horizon carbonate nodules are present, whereas the structure disappears. This soil is interpreted as a Luvisol.

36In the Luvisol (subunit 12b), two pollen assemblages have been analysed (fig. 8). In the Bt horizon, AP dominance indicates forest. A peak of Carpinus betulus L. pollen is observed (16.3 %) and Picea abies (L.) Karst. (12.2 %), Alnus sp. (10.2 %) and Salix sp. (6.1 %) also occur rather frequently. The Cyperaceae pollen percentage (18.4 %) is high. On the contrary, the pollen assemblage of the Eg horizon is of mesophytic steppe type, with significant predominance of NAP (70.6 %), mainly Cyperaceae (30.9 %), Poaceae (11.8 %) and Asteraceae (19.1 %). Pollen of xerophytes (Ephedra distachya L. and Chenopodiaceae) appear. The AP percentage is low, represented by a few finds of Pinus sylvestris L., Betula sp. and Ulmus sp.

37The upper soil (subunit 12a) consists of sandy silt, enriched in humus. In the voids, there are few microlaminated clay coatings. On the basis of these features, A and BCt horizons were distinguished. The latter partly overlies the lower soil. The soil is interpreted as an incipient Entic Podzol. The pollen assemblage of this soil (subunit 12a) is dominated by Pinus sylvestris L. (66.7 %) (fig. 8). A few pollen of Picea sp. occur.

38In the palaeogully (section #2-3, 11), the Retisol (unit 13) is overlain by a sand bed (unit 11) that is probably a gully alluvium (fig. 6b). An incipient Gleysol (subunit 11b), with prismatic structure, occurs within the gully alluvium. In the section #11, this Gleysol is underlaid by bedded pedosediments with frost fissures up to 0.7 m deep that open from the middle of the unit. Flints, rounded and angular up to 5 cm in diameter, occur in the upper subunit 11a. In sections #12-13, the unit 11 is a loess-like sandy silt (fig. 6c). A dense network of small frost fissures up to 1 m deep opens from the bottom of the unit 11. These structures are filled in with sand and they were primarily sand veins. In the section #2-3, the involutions in the forms of loading textures appear. Wedge- and cup-shaped fluvial-thermal erosional furrows up to 0.6-m-deep occur, filled in with layered sandy loam and including solid blocks of soil.

39The pedocomplex constituing unit 10 laterally turns into a Chernozem on the palaeoplateaux (section #1). In  other sections, the pedocomplex is made of two to four distinct soils. The types of the lower soils are dependent on their parent material. The Chernozem is definitely the stratigraphical marker as it is present in all sections. In the relief palaeodepressions (sections #2, 3, 5, 6), the Chernozem is underlaid by the forest soils and overlaid by the Cambisol (sections #3, 12, 13) (fig. 3). The forest soils, the Chernozem and the Cambisol constitute subunits 10c, 10b and 10a respectively.

40In sections #2-3, the soil 10c is represented by an incipient Albic Podzol, which includes А, E and BCs horizons (fig. 6b). In the BCs horizon, the appearance of iron-clay coatings held sand grains together. The soil is strongly disturbed by the subsequent bioturbation. The forest soil (subunit 10c) is also present in sections #5-6, and it includes A and BCtg horizons (fig. 6d). In the BCtg horizon, a large number of the clay coatings appear (fig. 7E). This soil is similar to an incipient Entic Podzol.

41The pollen assemblage of the Entic Podzol (subunit 10c) is of meadow-forest type (fig. 8). The AP dominates (40.1 %) and includes pollen of broad-leaved trees (Quercus robur L. and Carpinus betulus L.) with pollen of Betula pendula Roth. (11.7 %) and Pinus sylvestris L. (19 %) most prominant. The NAP percentage is also relatively high (31.4 %).

42The Chernozem (marker subunit 10b) is characterised by noticeable Mollic pedon, granular structure and many crotovinas in the lower part of the soil and in the subsoil. In the palaeogully (sections #2-3), the Chernozem is sandy, with features of podsolization and illuviation. In sections #12-13, features of weak podsolization and illuviation in the Chernozem are also present. On the contrary, in sections #5-6 there is no marks of podsolization, whereas the well-expressed crumb structure occurs (fig. 7d). Various forms of the Chernozem (unit 10b) are as follows. In sections #2-3, 12-13 this soil can be interpreted as a Luvic Chernozem (fig. 6c) and in sections #5-6 as a Haplic Chernozem.

43In the A horizon of the Luvic Chernozem (section #12), the pollen assemblage is a forb-grass steppe type (fig. 8). The NAP percentage is high (72.5 %) and Poaceae pollen is prominent (20 %). The percentages of xerophytic herbs increase, especially Ephedra distachya L. (5 %) and Chenopodiaceae (5 %), whereas those of Cyperaceae decrease (7.5 %). In the pollen assemblage of the AB horizon, xerophytes disappear, whereas the portion of forbs pollen become larger: Dipsacaceae (29.8 %), Asteraceae (10.2 %), Fabaceae (14.3 %), and Rosaceae (13.9 %). A few AP taxa (Betula sp. and Pinus sylvestris L.) occur.

44In sections #3, 12, 13, the Chernozem is overlaid by an incipient soil (subunit 10a) (fig. 6c). Locally, there is a thin loess layer between these soils. The soil of the unit 10a is composed of sandy silt and very slightly enriched in humus (0.41 %) (fig. 5). Numerous worm burrow fillings and earthworm granules occur. On the basis of these features, the soil is interpreted as a Cambisol. In the pollen assemblage of this soil (unit 10c), NAP is dominant (80 %), especially Cyperaceae (32.5 %) and Poaceae (15 %) (fig. 8). A few AP occur, noteably Alnus sp. and Pinus sylvestris L. Xerophyte pollen is found, especially those of Ephedra distachya L. (5 %).

45The unit 9 shows a facies of layered sands interpreted as a gully alluvium. The unit includes much of re-deposited soil material. Soil veins (0.5-1.5 m deep) and small frost fissures open from the lower part of the unit. On the slopes, the soil veins are bent by solifluction (fig. 9c), and, locally, so strongly that they become sub-horizontal. In sections #12-13, soil veins open from a loess-like bed (fig. 6c). It is possible that it corresponds to unit 9 as it lies between units 10a and 8. In this loess-like bed, well-preserved shells of Pupilla loessica have been found.

46In sections #12, 13, the unit 9 is overlaid by pedosediments, which in sections #2 and 3 turn into a relatively well-preserved soil. The soil includes A and ABkg horizons and is interpreted as a Cambisol. Soil veins and wedges, up to 2.5 m deep, open from the upper boundary of the unit. Almost all of them are bent by solifluction. Locally, the soils are disturbed by involutions in such a way that the underlying soil material protrudes up through small cracks. They can be related to involutions of type 2 (Vandenberghe, 1988). Locally, pedosediments sit in graben-like features that evidently formed, as well as involutions, during permafrost degradation (Murton & French, 1993; Vandenberghe, 2013; Van Vliet-Lanoё et al., 2016).

47In sections #2-4, an iron layer up to 4 cm thick is located in the middle of the unit 9, whereas in the plateaux sections, it is located in the lower part of the unit 8. This streak is visible everywhere in the Novyi Tik site. It was probably formed under hydromorphic conditions above an aquiclude layer of permafrost, and, thus, might indicate the upper boundary of permafrost during the later stadials.

4.2.6 - Loess I

48The unit comprises a thick loess with units of incipient soils (units 2, 4, 6). The lower loess unit (unit 7) is almost throughout disturbed by solifluction with numerous carbonates (fig. 7C). Sand fraction almost disappears. The pollen assemblage of the unit 7 is of a tundra-like type (fig. 8). The NAP percentage decreases (40 %), but spore frequency increases sharply (50 %). Palynomorphs of cryophytes (Betula sect. Nanae Alnaster fruticosus Ledeb., and Selaginella selaginoides (L.) Link.) appear.

49The first incipient soil (unit 6) is the most clearly expressed in the Loess I (fig. 3). The soil includes Ag and Bgk horizons. It is strongly gleyed, enriched in humus (0.6 %) and with an increase in clay particles (26.1 %) (fig. 5). Based on these features, the soil is interpreted as an Umbric Calcic Gleysol. In the palaeodepression (section # 2), the unit 6 is represented by pedosediments (fig. 3). The pollen assemblage of the unit 6 is of mesophytic steppe type (fig. 8). The NAP percentage is high (52 %), especially Cyperaceae (15.7 %), though the percentage of spores is high (27.4 %). Percentages of herbal xerophytes are also relatively high, mainly Artemisia sp. (5.5 %) and Chenopodiaceae (2.7 %). The AP is represented by Pinus sylvestris L. (20.6 %), and a few Pinus cembra L. (1.4 %).

50The thickest part of Loess I (unit 5) is enriched in coarse silt (65-68 %) (fig. 5). Big carbonate nodules up to 15 cm in diameter occur here. The lower part of the loess is deformed by solifluction and includes bedded post-cryogenic textures. The plastic deformation affecting the loess material is picked out by iron. On south-facing slopes, 0.4-m-deep cup-shaped fluvial-thermal erosional furrows occur, filled in with layered material (fig. 9b). Two incipient tundra-gley soils (subunits 5b and 5d) take place in the upper part of the loess.

51The unit 4 includes two incipient soils (subunits 4a and 4b) locally (section #2) separated by a thin loess bed. The lower incipient soil (subunit 4b) is a Gleysol (fig. 6a) locally disturbed by involutions. In section #3, it turns into pedosediments. Its NAP percentage is high (76 %) (fig. 8) and dominated by forbs (51.1 %), especially Asteraceae (12.9 %) and Lactuceae (24.2 %). A few pollen grains of Tilia cordata Mill. occur.

52The microstructure of the upper soil (subunit 4a) is well-aggregated, with complex granular and crumb microaggregates (fig. 7b). The amount of carbonate pedofeatures increases markedly. Numerous worm burrow fillings and earthworm granules appear. The soil is interpreted as a Gleyic Calcic Cambisol (fig. 6a). In this soil, the pollen assemblage is strongly dominated by NAP (78.4 %), espeсially Brassicaceae (32.4 %) (fig. 8). There is a relatively high percentage of the pollen of xerophytic herbs: Artemisia sp. (17.6 %), Ephedra distachya L. (4.1 %) and Chenopodiaceae (2.7 %). The AP percentage is low (20.3 %), and represented by Pinus sylvestris L., Betula pendula Roth., Alnus sp. and Salix sp.

53The loess units 3 and 1 are weakly developed and disturbed by Holocene bioturbation. The amount of carbonates increases and carbonate nodules up to 5 cm in diameter appear. A 2-m-deep ice-wedge cast filled in with a loess material (fig. 9a) opens from the lower loess (unit 3). A bigger one, up to 3 m deep and 1.5 m wide and filled in with material of a Gleysol, opens from the top of the unit 2. On the palaeoslope (sections #2, 3, 12, 13), the Gleysol (unit 2) occur, whereas on the palaeoplateaux (section #1), it is absent (fig. 3).

4.3 - Grain size distribution through the section

54Grain-size analyses of the Novyi Tik’s sediments (fig. 5) shows the following features. A bimodal fractional distribution is characteristic for the Pedocomplexes II and III and the units 3, 6 and 8. These beds have a large content of silt and a relatively high content of clay (20-30 %). Almost all units of the Loess I (with the exception of units 3 and 6) are characterised by unimodal, asymmetric, empirical, fractional distribution fields that indicate the dominance of a single geological agent in their formation.

55Pedocomplexes II and III are characterised by much coarse silt (40-68 %), though in the Pedocomplex III a large proportion of fine silt (up to 50 %) was observed. Clay gradually increases in this pedocomplexes: from 12 % in the Cambisol (unit 16a) to 30 % in the incipient Luvic Phaeozem (unit 18a). In the Loess II, the sand fraction appears, even though the grain-size is typical for a loess with a high percentage of coarse silt (72 %) and low сontent of clay (7-9 %).

56Soils and sediments of Pedocomplex I are characterised by a sharp increase in the content of sand (50-90 %), which reflects the intense erosion and soil re-deposition during these times. A significant increase in coarse sand (67 %) occurs in the gully alluvium (unit 11). Coarse flint fragments (rounded and unrounded) also occur here. An increase in clay content (17-27 %) is typical for the Bt horizons of soils (unit 14b) and for the BCg horizon of the Cambisol (unit 8).

57The units of the Loess I have a high content of the coarse silt (‘loess fraction’) from 42 % in unit 3 to 68 % in unit 5. A relatively high clay content (26-32 %) is observed in the units 3 and 6. Slightly lower percentages of clay are found in other units of the Loess I: from 10 % in unit 5 to 23 % in unit 4.

58Five levels of inclusions of flint (up to 3-4 cm) were found. The two upper of them are located within units of gully alluvium (units 11 and 13). Furthermore, flint inclusions within Loess II and at the lower boundary of Loess III (solifluction horizon) occur. Two fragments of flint within the unit 21 also have been found. Inclusions of flint evidently indicate erosion phases. The source of flint is most likely limestone formation upward the slope.

59The units of the Loess I, II, III and pedocomplexes II and III are characterised by small sizes of average particle diameter (Mz = 7-20 µm). However, in the Pedocomplex I, the average particle size increases significantly from 50 µm in the Cambisol (unit 8) to 340 µm in the lower part of the gully alluvium (unit 11). The increase in the average particle size in the Pedocomplex I has been noted in many sections of the Volyn’ Upland (Bonchkovskyi, 2019).

4.4 - Archaeological artefacts

60In section #2, two archaeological artefacts have been found at different levels. In the BCs horizon of the Podzol (subunit 10c), a Levallois core nucleus has been found. The archaeological identification of the artefact was made by L. Kulakovska and V. Usik (Institute of Archaeology of National Academy of Science of Ukraine). Near to the lower boundary of the unit 5 (a loess bed), a split bone of Mammuthus primigenius has been found. The identification of the bone was made by B. Ridush (Yuriy Fedkovych National University of Chernivtsi) who considers that, according to the type of the breakage, the bone was split by Palaeolithic humans.

5 - Discussion

5.1 - Chronostratigraphic attributions

5.1.1 - Stratigraphical frameworks and pedostra-tigraphical subdivisions in Ukraine

61In order to determine the chronostratigrpahic attribution of the units and subunits at Novyi Tik, the correlation with the well-studied and dated sections is necessary. The correlation was carried out with the closely located sequences at Korshiv and Boyanychi (Kusiak et al., 2012; Fedorowicz et al., 2013; Bogucki & Voloshyn, 2014), on one hand, and Central Ukrainian sections with their detailed stratigraphy (Veklitch et al., 1984; Gerasimenko, 1988; 2006; Rousseau et al., 2001; Gerasimenko & Rousseau, 2008; Bokhorst et al.,2009; Karmazinenko, 2010; Haesaerts et al., 2016), on the other (fig. 10). It should be mentioned that different stratigraphical frameworks are applied for the loess-palaeosol sequences in Western Ukraine: the regional stratigraphic scheme of Western Ukraine (Bogucki, 1986; Bogucki et al., 2014) and the Quaternary stratigraphical framework of Ukraine established by Veklitch et al. (1993) and modified by Gerasimenko (2004), Gozhik et al. (2000; 2014) and Matviishyna et al. (2010). The majority of the units within the frameworks are shown to be equivalents but the attribution of the Dnipro and Kaydaky chronostratigraphic units are different in various publications (Rousseau et al., 2001; Gerasimenko, 2006; Lindner et al., 2006; Łanczont & Boguckyj, 2007; Bogucki et al., 2012; Łanczont et al., 2014; Haesaerts et al., 2016).

62In the Ukrainian Quaternary framework (Veklitch, 1982; Veklitch et al., 1993), loess and palaeosol units are subdivided into subunits, e.g. the Kaydaky unit is subdivided into ‘kd¹’ (pedocomplex), ‘kd²’ (loess) and ‘kd³’ (pedocomplex). Loess subunits are frequently associated with cryogenic features. In Ukrainian palaeopedology (Veklitch et al., 1979; Sirenko & Turlo, 1986), the initial, optimal and final phases of soil formation are distinguished in soils of interglacials and interstadials. They are marked by the indices ‘a’, ‘b’ and ‘c’, respectively. If the optimal phase of pedogenesis (‘b’) is represented by two soils, additional numerical indices (‘b¹’ and ‘b²’) are introduced. Initial, optimal and final phases of pedogenesis are also distinguished within subunits (e.g. ‘kd^1a’, ‘pl^3b2’).

5.1.2 - Correlation of the Novyi Tik sequence

5.1.2.1 - Pedocomplex I

63One of the ways to achieve the reliable correlation of the sections is a comparison of their marker horizons. The most pronounced stratigraphic marker, revealed in loess-palaeosol sequences of both Western and Central Ukraine, is the Chernozem, underlied by the forest soil, within Pedocomplex I. At Novyi Tik, this Chernozem corresponds to subunit 10b. At Korshiv and Boyanychi, it is related to Kolodiiv (Upper Horohiv) soil, which is dated to 76.3 ± 9.2 and 83.1 ± 14.1 ka (Fedorowicz et al., 2013) and to 101 ± 13 ka (Kusiak et al., 2012). In the Middle Dnipro area, the Chernozem is related to the part of the Pryluky unit, namely to the ‘pl^1b2’ soil (Veklitch et al., 1984; Gerasimenko, 1988; Rousseau et al., 2001; Gerasimenko & Rousseau, 2008), and it is dated to 95 ± 8 ka (Karmazinenko, 2010).

64These most pronounced Chernozems within the Kolodiiv and Pryluky units are underlaid by one or several forest soils. In the western Ukraine, one soil is usually described, and it is regarded as the Horohiv soil, assignable to the last interglacial (Morozova, 1981; Bogucki, 1986; Gozhik et al., 2000; Lindner et al., 2002, 2006; Jary, 2009; Bezusko et al., 2011; Bogucki et al., 2014). Locally, a loess bed and cryogenic features occur between the Chernozem and the forest soil (Nechaev, 1983; Bogucki, 1986). In the Middle Dnipro Area, comparative studies of this Pedocomplex I on plateaux and on slopes demonstrate that the single forest soil of the plateaux corresponds on slopes to the lowest of the set of forest soils located below the Chernozem. This lowest soil is related to the Kaydaky unit (Veklitch, 1968, 1982; Veklitch et al., 1984; Matviishyna et al., 2010). By palaeopedological and pollen data, it is demonstrated to have formed during the last (Mikulino) interglacial (Gerasimenko, 1988, 2006; Rousseau et al., 2001; Haesaerts et al., 2016). It is widely accepted that Mikulino interglacial is an equivalent of the Eemian (Grichuk, 1989; Bolikhovskaya, 1995). At Novyi Tik (section #1, palaeogully on a plateau), the Pedocomplex I consists of an upper Chernozem and a lower forest soil, separated by cryogenic features. Thus, the well-pronounced Chernozem of unit 10 at Novyi Tik corresponds to the ‘pl^1b2’ and Kolodiiv soils, whereas the lower soil (units 12-14) corresponds to the last interglacial soil according to the pollen assemblages. It is thus correlated with the Horohiv soil in the Western Ukraine and with Kaydaky soil in the Central Ukraine.

65At Novyi Tik, in palaeodepressions, the Pedocomplex I includes a soil succession, which is very similar to those described in the Middle Dnipro Area (Rousseau et al., 2001; Gerasimenko, 2006) (fig. 10). The pollen assemblage of the lowest soil (unit 14b) might be correlated with the pollen zone M3 (mixed forest) of the Mikulino interglacial in Russia (Grichuk, 1989). It corresponds to the transition from the initial phase of the Kaydaky interglacial (‘kd^1a’) to the optimum (‘kd^1b’) (Gerasimenko, 2004). Due to a relatively high content of pollen of broad-leaved trees (Carpinus, Ulmus, Quercus) in the Retisol (unit 12a), the corresponding pollen zone might be correlated with M4 zone of the Mikulino interglacial in Russia (Grichuk, 1989), which in Ukraine takes place in the ‘kd^1b1’ soil (Gerasimenko, 2004). The pollen assemblage from the Bt horizon of the Luvisol (unit 12b) evidently corresponds to the M6 (Carpinus) pollen zone of the Mikulino interglacial in Russia (Grichuk, 1989) and, on the basis of palynological data, to the ‘kd^3b1’ phase in Central Ukraine (Gerasimenko, 2004).

66The Entic Podzol (unit 12a) could be the youngest soil of the last interglacial. The pollen assemblage of its subsoil is of mesophytic steppe type, whereas the Entic Podzol’s pollen assemblage is of boreal forest type. This reflects a gradual cooling and aridification at the end of the interglacial, which took place at the end of the Eemian (Caspers et al., 2002; Kukla et al., 2002). The soil is richer in humus than the other soils of the last interglacial, which is typical for the ‘kd^3b2’ soil in the Central Ukraine (Gerasimenko, 2006).

67At Novyi Tik, the marker Chernozem soil (unit 10b) turns into a well-developed pedocomplex in palaeodepressions. The soil succession of this pedocomplex is clearly correlated with the Pryluky pedocomplex at Vyasivok sequence (Rousseau et al., 2001; Haesaerts et al., 2016) (fig. 10). The marker Chernozem is attributed to the ‘pl^1b2’ soil there, whereas the underlying forest soil (subunit 10c) is attributed to the ‘pl^1b1’soil. The pollen assemblage of the unit 10c includes broad-leaved trees (Quercus robur L. and Carpinus betulus L.), which is typical for the ‘pl^1b1’ soil in Central Ukraine (Gerasimenko, 2006), to which it is correlated. The Cambisol (unit 10a) had not yet been found in other sites of Ukraine. We tentatively suggest to correlate it with the ‘pl^1b2-y’ soil (Haesaerts et al., 2016). Similar Cambisols, overlying the marker Chernozem, have been discovered in the Boremel and Novostav sections (Volyn’ Upland) (Bonchkovskyi, 2017, 2019).

68The bed of gully alluvium and loess silt with cryogenic features (unit 9) probably corresponds to the ‘pl²’ loess unit at Vyasivok, whereas the Cambisol (unit 8) might be correlated with the ‘pl^3b’ in the Middle Dnipro area (Rousseau et al., 2001; Gerasimenko, 2006; Haesaerts et al., 2016). The loess bed between Kaydaky and Pryluky pedocomplexes is attributed to the Tyasmyn (‘ts’) unit (Veklitch, 1968; Veklitch et al., 1984; 1993; Gerasimenko, 2006; Matviishyna et al., 2010). The loess bed as well as gully alluvium (unit 11) with cryogenic features at Novyi Tik can be tentatively correlated with the Tyasmyn unit due to its position between pedocomplexes of the last interglacial and the first interstadial of the last glacial. However, the stratigraphic position of a Gleysol (subunit 11b) within the gully alluvium remains unclear. Thus, at Novyi Tik, the units 8-10 correspond to the Pryluky unit, the unit 11 to the Tyasmyn unit, and the units 12-14 to the Kaydaky unit of the Ukrainian Quaternary framework.

69In the most complete sections of Western Ukraine (Kolodiiv and Pronyatyn), three Kolodiiv soils have been identified, separated by levels affected by cryogenesis and by loess beds (Łanczont & Boguckyj, 2007; Łanczont et al., 2015). The lower soil (Kolodiiv-3) was formed under a forest-steppe, whereas the younger soils (Kolodiiv-1 and Kolodiiv-2) are steppe-type soils. It is likely that the forest soil (subunit 10c) at Novyi Tik corresponds to Kolodiiv-3 soil, whereas the Chernozem (subunit 10b) to Kolodiiv-2 and Cambisol (unit 8) to Kolodiiv-1.

5.1.2.2 - Loess I

70At Novyi Tik, the Loess I comprises three Gleysols (units 2, 4, 6) that can clearly be correlated with Gleysols at Korshiv and Boyanychi (fig. 10). The lower Gleysol (unit 6), which is enriched in humus and overlaid by the thickest loess horizon, is a correlative of the Dubno soil (Bogucki et al., 2014) by its pedomorphology. Its pollen assemblage is in addition very similar to the optimum of the Dubno interstadial (Bezusko, 2013). The Dubno unit is dated to 27.0 ± 3.2, 46.8 ± 5.4, 46.8 ± 5.4 and 44.1 ± 5.4 ka at Korshiv (Fedorowicz et al., 2013), and to 48.6 ± 6.3 ka at Boyanychi (Kusiak et al., 2012). At Stari Bezradychi in the Middle Dnipro area, the Vytachiv unit is dated to 36.3 ± 3.4, 47.4 ± 4.4 and 47.3 ± 5.3 ka (Bokhorst et al., 2009). Thus, the Dubno unit as well as unit 6 at Novyi Tik site correspond to the Vytachiv unit of Central Ukraine, represented by a Cambisol instead of a Gleysol (Sirenko & Turlo, 1986; Gerasimenko, 2006; Karmazinenko, 2010).

71The main loess bed (unit 5) with two tundra-gleys at Novyi Tik undoubtedly corresponds to the thickest loess unit (Bug unit) in Central Ukraine, therein several incipient soils (Gerasimenko & Rousseau, 2008; Rousseau et al., 2011; Veres et al., 2018) occur. The Bug loess is overlaid by the Rivne unit in Western Ukraine (Bogucki, 1986) and by the Dofinivka unit in Central Ukraine (Veklitch et al., 1993). The Rivne unit is dated at Korshiv to 20.4 ± 2.7, 23.2 ± 2.7 and 22.5 ± 2.5 ka, and at Boyanychi to 20.9 ± 2.7 ka (Kusiak et al., 2012; Fedorowicz et al., 2013). The unit 4 at Novyi Tik, which overlays the thickest loess, might correspond both to the Rivne and Dofinivka units. However, based on the palynological and palaeopedological data, the upper soil of unit 4 at Novyi Tik was formed under a cooler and drier climate than that reconstructed from the other sections of Dofinivka unit in Ukraine (Matviishyna, 1982; Sirenko & Turlo, 1986; Gerasimenko, 2004; Doroshkevych, 2018).

72The upper Gleysol (unit 2) at Novyi Tik is likely a correlative of the Krasyliv unit at Korshiv and Boyanychi. The Krasyliv unit is dated to 15.8 ± 1.5 ka in the Boyanychi section. The largest ice wedge casts open exactly from the Krasyliv unit (Bogucki et al., 1975; Nechaev, 1983; Dolecki, 2003; Jary, 2009), the same as from unit 2 at Novyi Tik. The infilling of the ice-wedge pseudomorph that opens from Krasyliv unit is dated to 15.4 ± 0.8, 17.4 ± 0.9, 16.1 ± 0.9 and 19.6 ± 1.0 ka (Fedorowicz et al., 2018). According to Bogucki et al. (2012), the Krasyliv unit corresponds to the middle subunit of the Prychornomorya unit (‘pc²’). Thus, the units 1 and 3 at Novyi Tik might correspond to subunits ‘pc³’ and ‘pc¹’ of the Prychornomorya unit, respectively.

5.1.2.3 - Pedocomplex II and Loess II

73The Korshiv unit is an important marker in the loess-palaeosol sequences of Western Ukraine due to both upper Chernozem soil and lower Luvisol (Bogucki, 1986; Bogucki et al., 2007b; Palamarchuk, 2011; Fedorowicz et al., 2013; Łanczont et al., 2014). Locally, a thin loess between soils occur (Alexandrowicz et al., 2014). The correlation between the Pedocomplex II and the Korshiv pedocomplex at Novyi Tik and Korshiv sections is clear. Particularly, the Pedocomplex II comprises an upper Chernozem soil dissected by a network of soil veins, and a lower Luvisol. As in the Korshiv section (Fedorowicz et al., 2013), the lower soil includes a remarkable A horizon, interpreted as a separate incipient Luvic Phaeozem (unit 18a). It is widely accepted that the Korshiv pedocomplex corresponds to MIS 7 (Bogucki et al., 2007b). The Potyagaylivka soil (‘pt’) is correlated with MIS 7 in Central Ukraine (Gerasimenko & Matviishyna, 2007) and is defined as the first soil complex under the marker unit of the till (Veklitch, 1968; Gozhik & Gerasimenko, 2011). The Potyagaylivka unit at Vyasivok-4 site (Gerasimenko, 1988) as well as Stari Kaydaky site (Gerasimenko, 2019) is similar to Pedocomplex II in Novyi Tik. The pollen assemblages of both the Pedocomplex II and the Potyagaylivka unit (Gozhik & Gerasimenko, 2011) represent the aridification and decline of trees towards the end of the warm stage. The Pedocomplex II at Novyi Tik site includes several soils (units 16 and 18) and loess (unit 17), which would be appropriate to mark as ‘pt¹’, ‘pt³’ for soils and ‘pt²’ for the loess bed.

74The truncated Loess II at Novyi Tik corresponds to the thick loess horizon (L2 according to Boguckyj et al., 2009) between the Horohiv and Korshiv pedocomplexes in Western Ukraine. The plicately deformed Gleysol (Ternopil unit) at Korhsiv and Boyanychi sites is revealed in the lower part of the L2 and dated to 159 ± 53 ka (Kusiak et al., 2012; Fedorowicz et al., 2013). A similar Gleysol (unit 15b) occurring at Novyi Tik in the lower part of the Loess II may correspond to the Ternopil unit. Moreover, a thick loess between the Kaydaky and Potyagaylivka soil is marked as the Dnipro unit (‘dn’) (Veklitch, 1968; Gerasimenko, 2004). Including a till unit in Northern Ukraine, this latter is considered as a marker horizon (Veklitch, 1982; Gozhik & Gerasimenko, 2011). It is likely that Loess II at Novyi Tik site corresponds to Dnipro unit.

5.1.2.4 - Pedocomplex III and Loess III

75The first soil unit under the Korshiv pedocomplex in the Western Ukraine is the Luck soil (Fedorowicz et al., 2013; Bogucki & Voloshyn, 2014). The pedological features of the Luck soil are very similar to those of the forest soil in Pedocomplex III at Novyi Tik despite the latter is less disturbed by solifluction. Both Luck soil and the forest soil of Pedocomplex III at Novyi Tik are more podzolised and have less prominent A horizon than the Korshiv soils. The Luck soil has been correlated with MIS 9 (Lindner et al., 2004; 2006; Alexandrowicz et al., 2014).

76In Central Ukraine, the Upper Zavadivka unit (‘zv³’) was correlated to MIS 9 (Gerasimenko, 2004; Gerasimenko & Matviishyna, 2007; Gozhik & Gerasimenko, 2011). The ‘zv³’ unit consists of two soils: an upper Chernozem and a lower Luvisol. The soil succession of the Pedocomplex III at Novyi Tik is similar to the ‘zv³’ unit, although the upper soil at Novyi Tik is significantly less pronounced. The gleyed loess-like silt underlying Pedocomplex III at Novyi Tik probably corresponds to loess unit ‘zv²’ in Central Ukraine (Vozgrin, 1990; Gozhik & Gerasimenko, 2011). Then, the Loess III might corresponds to Oril (‘or’) loess unit, which separates the Upper Zavadivka and Potyagaylivka pedocomplexes (Veklitch, 1968; Gozhik et al., 2000; Gerasimenko & Matviishyna, 2007).

77Thus, correlation of the site studied with regional stratigraphical framework by Bogucki (1986; Łanczont & Boguckyj, 2007) and with the Ukrainian Quaternary framework (Veklitch et al., 1993; Gerasimenko, 2004; Matviishyna et al., 2010) is proposed as follows (fig. 11). The correlation enables the comparison of the main units of the Novyi Tik sequence with the LR04 curve of Lisiecki and Raymo (2005) (fig. 12).

5.2 - Palaeoenvironmental reconstructions

5.2.1 - Sub-sequence I

78The sub-sequence I includes Pedocomplex III (Upper Zavadivka) and Loess III (Oril). During the formation of Pedocomplex III in the Upper Zavadivka period (MIS 9), the palaeolandscape succession was as follows. At the end of the preceding ‘zv²’ time unit (MIS 10), there were contrasting landscapes of a cold climate – sparse spruce-pine forest alternated with grassland in which Ephedra played a rather significant role. At the beginning of the late Zavadivka times (‘zv^3a’?), the climate was relatively dry, as evidenced by a slight increase in soil humus and the absolute predominance of pine in the pollen record from the lower part of the Luvisol ‘zv^3b1’ (subunit 20b). During the formation of this Luvisol, pine, spruce and broad-leaved trees (oak, elm and hazel) shared dominance in the forests in which ground cover was weakly developed. Based on pedomorphological features of the Luvisol and the spread of broad-leaved trees, the phase ‘zv^3b1’ may correspond to an interglacial, probably to 9e sub-stage of MIS 9 (fig. 12).

79During the times ‘zv^3b2’ (subunit 20a), climate aridification took place, which led to the activation of humus accumulation. Nevertheless, the processes of lessivage and podzolization also occurred. Landscapes were again contrasting. An incipient Gleyic Luvic Phaeozem formed, under sparse birch‑pine forest, and patches of mesophytic steppe with admixtures of xerophytes (Ephedra distachya L., Chenopodiaceae). The spread of open landscapes led to an increase in the activity of the soil fauna. The disappearance of broad-leaved taxa indicates a cooling of the climate, compared to the phase ‘zv^3b1’, therefore this time span could be regarded as an interstadial. Moreover, the cold event between the two phases of soil formation (subunits 20a and 20b) are marked by soil veins, which open from top of the lower soil.

80During the beginning of the Oril period (MIS 8), a relatively wet and cold climate led to activation of cryogenic processes, particularly of solifluction and soil vein formation. Erosion also took place. Cryogenic features are not clear evidence that permafrost existed. Nevertheless, small ice-wedge casts in other sections in the Volyn’ Upland at this level (Bogucki et al., 1996) indicate that there was probably sporadic or discontinuous permafrost at that time as it is seen in the modern analogues (Kudryavtsev, 1978; Romanovskiy, 1993; Murton & Kolstrup, 2003). During the second half of the cold stage, cryogenic processes stopped whereas loess accumulation took place.

5.2.2 - Sub-sequence II

81The sub-sequence II includes Pedocomplex II (Potyagaylivka) and Loess II (Dnipro). Previous studies in the region of the Potyagaylivka (= Korshiv) soil (the terrestrial analogue of MIS 7) have shown that there were two phases in its formation: an early phase of forest pedogenesis and a late phase of Chernozem formation (Bogucki, 1986; Bogucki et al., 2007b; Palamarchuk, 2011). Nevertheless, in recent studies as many as four phases of pedogenesis have been distinguished (Fedorowicz et al., 2013; Łanczont et al., 2014). Studies conducted at Novyi Tik have confirmed the existence of four warm and two cold phases during the Potyagaylivka times.

82Luvisol (subunit 18b) was formed during the early phase, ‘pt^1b1’, which has less distinct signs of lessivage than in the lower Zavadivka soil (Pedocomplex III), that is, fewer clay coatings and more of its destruction. The interglacial climate of the phase ‘pt^1b1’ (subunit 18b) is evidenced by the very high pollen percentages of broad-leaved trees (71.8 %). Lime forests with mesophytic ground cover were widely spread. Therefore, we suggest to correlate this phase with sub-stage 7e of MIS 7 (fig. 12).

83During the phase ‘pt^1b2’, climate aridification occurred, which led to the activation of the humus accumulation and to the appearance of xerophytes (Ephedra distachya L., Chenopodiaceae) in the vegetation composition. Incipient Luvic Phaeozems (subunit 18a) were formed under mesophytic steppe with patches of pine forests. Association of willow and alder occupied valleys and wet depressions. The soil has features of lessivage (such as clay coatings in the channels), as well as chemical weathering. The absence of the pollen of broad-leaved trees may indicate the climate cooling, compared to the early phase. Probably, it represents the final phase of the interglacial.

84Significant cooling of the climate is represented in ‘pt²’ times by a bed of loess-like silt (unit 17). At the beginning of the cold phase, sparse birch-pine forests with abundant herbs spread, in which shrub birch appeared for the first time since the beginning of the whole described period. According to micromorphological data, it is possible to identify the initial pedogenesis as having been of a podzolic type. There were processes of lessivage, podzolization and colloid translocation (in the form of microlaminated clay coatings) at the very end of ‘pt^1b2’ soil formation (subunit 18a). At the end of cold phase ‘pt²’, the severity and aridity of the climate increased, and loess accumulation and cryogenesis resumed. There was the spread of subperiglacial spruce-pine associations together with cryophytes (mainly Betula sect. Nanae) and xerophytes (mainly Ephedra distachia L.). Alder associations probably occurred in the valleys. Based on all these features, the ‘pt²’ phase was a stadial that might have been the first stadial of MIS 7 (7d sub-stage) (fig. 12).

85During the later Potyagaylivka times ‘pt^3b’ (subunit 16b), leached Chernozems were formed under a mesophytic steppe with rare xerophytes (Ephedra distachya L., Artemisia sp., Chenopodiaceae). In places, broad-leaved forests (of oak, hornbeam, elm and hazel) and juniper thickets also occurred. In the soil, the presence of single clay coating in the channels indicate initial lessivage, whereas the soil fabric reflects the contrasting conditions of wetting and drying. The soil is well-aggregated, with complex biogenic aggregates and coprolites, which demonstrates intense humus accumulation. Much bioturbation in the subsoil indicates one of the most prominent phases of pedofaunal activity. On the basis of the palynological and paleopedological data, this phase was less warm and humid that the ‘pt^1b1’, therefore we suggest to correlate the ‘pt^3b’ phase with the first interstadial of MIS 7 (7c sub-stage) (fig. 12).

86The uppermost soil of the Pedocomplex II (subunit 16a), interpreted as Cambisol, was formed under meadow-steppe at the end of Potyagaylivka times (during the ‘pt^3c’ phase). The disappearance of broad-leaved species (except Corylus) was probably due to a general trend towards a cooler climate. Pedogenesis included active humus accumulation and biogenic aggregation of the material, but traces of lessivage and colloid translocation are more pronounced than in the soil below. The dense system of soil wedges and veins, which opens between the subunits 16a and 16b soils, as well as, in places, a loess streak, mark a significant cooling event. The climate probably was arid and cold, but there was no permafrost. Probably, the cooling event correspons to second stadial of MIS 7 (7b sub-stage), whereas the ‘pt^3c’ phase to the interstadial of the 7a sub-stage (fig. 12).

87Activation of solifluction, formation of patterned ground and a network of soil veins indicate wet and cold climate during the early Dnipro times (MIS 6). Modern patterned ground is formed in permafrost (Mackay, 1979; Popov et al., 1985; Romanovskiy, 1993; Bertran et al., 2017), so it can be assumed that permafrost existed, at least, at the beginning of the Dnipro time. Partially eroded ice-wedge casts indicate a cryogenic event in the mid Dnipro times, when solifluction was presumably happening on the slopes. At the beginning of the phase, there was probably a slight warming of the climate (the Ternopil times), when an incipient Gleysol (subunit 15b) was formed. By the end of the Dnipro times, loess accumulation and erosion has become more active. Erosion processes led to almost complete denudation of loesses, and the re-deposition of a few rounded flint pebbles, which bear the signs of frost cracking.

5.2.3 - Sub-sequence III

88The sub-sequence III is characterised by the most complicated structure and includes Pedocomplex I and Loess I. As it was described above, the Pedocomplex I was formed during the Kaydaky (units 12-14), Tyasmyn (unit 11) and Pryluky (units 8-10) times. Due to several phases of erosion during Kaydaky (Horohiv) times (MIS 5e), the soils (Podzols and Luvisols) were mainly eroded and re-deposited. A detailed study of the sections, particularly in the sedimentation traps, allows the reconstruction of the general trend of environmental development during the Kaydaky times. In the palaeodepressions, at the beginning of the Kaydaky times (phase ‘kd^1a’), Gleysol (subunit 14b) was formed under a cover of sparse birch forest with dense forbs ground cover.

89During the ‘kd^1b’ phase, Stagnic Retisol (subunit 14a) was formed under broad-leaved forest (elm, oak, hornbeam), with an admixture of birch, pine and spruce, and with the mesophytic ground cover. As earlier, alder associations occupied the valleys. Soils at that time were frequently eroded or re-deposited.

90During the ‘kd³’ phase, two subphases – an early wetter one (‘kd^3b1’) and a later slightly drier one (‘kd^3b2’) − have been documented. During the first subphase, a Luvisol (subunit 12b) formed under spruce-hornbeam forest with abundant cover of fern and mosses. Dense alder associations with sedges occupied the wetlands. The spread of highly mesophillous genera (hornbeam, spruce and hop) and the presence of typical hygrophytes in the vegetation cover (alder, willow, sedges) indicate a highly humid climate, which leads to the correlation of this phase with the time corresponding to M6 (Carpinus) zone of Mikulino interglacial, established by Grichuk (1989). During the late subphase – ‘kd^3b2’, Entic Podzol was formed under mesophytic steppes, with elm-birch woodland. Broad-leaved species (except Ulmus) disappeared at that time, whereas xerophytes (Ephedra distachya L. and Chenopodiaceae) appeared. The climate become cooler and drier. By the end of the Kaydaky times, pine forests with an admixture of spruce had spread, as well as an abundant fern and club-moss cover. Pollen data obtained allows the suggestion that the Entic Podzol with pronounced mollic pedon was actually formed in two phases. At first (‘kd^3b2’) there was humus accumulation under mesophytic steppe, and later on (the ‘kd^3c’? phase), a strong podzolisation developed under boreal pine forests.

91Erosion and accumulation of gully alluvium (unit 11) occurred, and loess-like sandy loam deposition on the plateaux represents the Tyasmyn stadial (MIS 5d). At the beginning of the Tyasmyn stadial, a dense network of frost fissures formed, which reflect a dry and continental climate (Kudryavtsev, 1978). In wet depressions, involutions grew as well as cryogenic block subsidence. The latter has been regarded as the result from reticulate ice melting (Van Vliet-Lanoё et al., 2016).

92In the most complete sections of Western Ukraine, three interstadial soils (Kolodiiv unit) have been identified, separated by levels affected by cryogenesis as well as by loess beds, which are correlated with the Pryluky unit (Łanczont & Boguckyj, 2007; Łanczont et al., 2015). In the Novyi Tik section, four phases of pedogenesis (units 8 and subunits 10a, 10b, 10c) and a phase of significant cooling (unit 9) have been distinguished.

93The lowest soil (subunit 10c) with marked podsolization formed under light birch-pine forest with an admixture of broad-leaved trees (mainly oak and hornbeam) during the ‘pl^1b1’ phase. Patches of meadow-steppe also existed. Willow and alder associations occupied wet depressions. Different soil types were formed on the various parent substrates: e.g. on the gully sands Albic Podzol (sections #2-3), on the sandy loam Entic Podzol. Considering the high role of broad-leaved tree species in the woods (the largest in the Pryluky times), it is assumed the ‘pl^1b1’ phase to have been the climatic optimum of the Pryluky times, and believe that the climate at this time was close to subboreal. The large extende of hygrophytes (Salix, Alnus, and Cyperaceae), club-mosses, ferns and green mosses, as well as the soil characteristics, all indicate a humid climate.

94The Chernozem (subunit 10b) formed during the phase ‘pl^1b2’ indicates a significant aridification. Differences in the grain size of parent substrate materials determined how pedogenesis developed. A Luvic Chernozem formed on the sandy loam and the loess-like sandy loam, and a Haplic Chernozem on the silty loam. Soils show weak signs of podzolization and clay translocation downward into AB horizon. According to the pollen data, there was some increase in aridity by the end of the phase: meadow-steppe vegetation was replaced by forb-grass steppe with xerophytic associations (from Ephedra distachya L. and Chenopodiaceae). Based on pollen data, the same trend towards increasing aridity has been identified at the end of this phase in the Kolodezhy section (the Volyn’ Upland) where light birch-pine forests was replaced by forb-grass steppe. The disappearance of broad-leaved species probably points to a cooling and development of boreal vegetation.

95A slight increase in ambient moisture at the end of Pryluky times caused a final phase of pedogenesis (‘pl^1b2‑y’),
when Cambisol (unit 10a) formed under mesophytic steppe. In wet depressions, alder grew.

96A thin loess-like silt bed (unit 9) with shells of Pupilla loessica marked a significant cooling (‘pl²’), which can be correlated with MIS 5b. On slopes, first solifluction and then erosion occurred. A network of soil veins formed, probably under deep freezing conditions. During the late Pryluky times (‘pl³’), the strong erosion led to redeposition of soil material. Locally, there is a well-preserved soil (unit 8), interpreted as Cambisol. This may indicate an interstadial, correlated with 5a sub-stage of MIS 5 (see fig. 12).

97The whole Loess I probably formed during Pleniglacial. The Gleysols (units 2, 4, 6) represents interstadials and loess units (#1, 3, 5, 7) stadials. The lowest loess unit (unit 7) formed during Uday (MIS 4) times. The limited thickness of the unit, as in other sections of the Volyn’ Upland, and the increased clay content and reduced coarse silt, probably indicate less intense aeolian accumulation than during other stadials. Tundra landscapes existed, with cryophytes: Betula sect. Nanae, Alnaster fruticosus Ledeb. and Selaginella selaginoides (L.) Link. On slopes, solifluction occurred, which bent soil veins. Involutions as well as cryogenic subsidence, caused by reticulate ice melting, also took place. The morphology of cryogenic features is not a sure indicator of the existence of permafrost. However, earlier investigations have shown that permafrost most likely existed (Nechaev, 1983; Dolecki, 2003; Bonchkovskyi, 2018).

98The first interstadial soil (unit 6) probably formed during Vytachiv (MIS 3) times. Calcic Gleysols and Umbric Calcic Gleysols (on the plateaux) formed under boreal mesophytic steppe, with patches of sparse pine forest, including Pinus cembra L. The high percentage of pollen of xerophytic (Artemisia, Chenopodiaceae) and hygrophytic (Cyperaceae) plants is an indicator of contrasting edaphic conditions (Bezusko, 2013). Humus accumulation took a noticeable part in the pedogenesis, but the humus was predominantly of moder or mull-like moder type, indicating acid conditions of soil formation. Erosion and redeposition of soils also occurred.

99The main (Bug) loess (unit 5) with a high content of coarse silt (65-68 %) formed during the first half of the Late Pleniglacial (Gerasimenko, 2004). At the beginning of the stadial, solifluction and erosion occurred. Above the solifluction horizon, there are two incipient soils (tundra gleys), also known from other sections of Northern Ukraine (Gerasimenko, 2006; Rousseau et al., 2011; Veres et al., 2018).

100A special feature of the Bug loess at Novyi Tik is the presence of very large carbonate nodules up to 15-cm-large, whose genesis is explained in different ways (Kovda, 2004; Barta, 2011; Zaidelman & Nikiforova, 2001). The most plausible hypothesis is that the nodules formed in ground moisture over a level of local water resistance under conditions of alternating pronounced arid and humid seasons, with the rhythmic flow of carbonate solutions (Kovda, 2004). During Bug times, ground moisture was due to the existence of a waterproof permafrost layer. Moreover, carbonate nodules are mainly located in a palaeorelief depression.

101Two incipient soils (subunits 4a and 4b) formed under interstadial conditions during Dofinivka times. During the earlier phase ‘df¹’, an incipient Gleysol formed under boreal mesophytic steppe with patches of light pine-birch forests and a small admixture of lime. During the later phase ‘df³’, Gleyic Calcic Cambisol formed under northern-boreal forb-grass steppe with xerophytes (Artemisia, Chenopodiaceae, Ephedra distachya L.) and patches of light birch-pine forest. Considering the presence of lime and the absence of xerophytes, the large extend of Cyperaceae, and the soil genesis, we assume that the phase ‘df¹’ was warmer and wetter than the later. During ‘df³’ phase, humus accumulation, as well as biogenic aggregation, took place.

102At the end of the Pleistocene (Prychornomorya times) two thin loesses (units 1 and 3) and Gleysol (unit 2) formed. The latter formed during the warm phase ‘pc²’. The soil is characterised by the processes of initial pseudogleying and biogenic aggregation. Two cryogenic events are recorded, during which formed a network of the largest ice-wedge casts. Such palaeocryogenic features indicate continuous permafrost at these times, as already documented (Bogucki et al., 1975; Nechaev, 1983; Jary, 2009; Bonchkovskyi, 2018). According to Fedorowicz et al. (2018), the formation of the largest ice-wedge casts took place between 16.1 and 13.9 ka and may be correlated with Heinrich event (H1).

103The palynological and palaeopedological studies of the Novyi Tik sequence enables a more detailed comparison with the LR04 curve of Lisiecki and Raymo (2005) (fig. 12), e.g. the units of both Pedocomplexes I and II can be correlated with MIS 5 and MIS 7 sub-stages.

6 - Conclusions

104The loess-palaeosol sequence at Novyi Tik demonstrates significant lateral changes in facies, mainly caused by the palaeorelief. A very detailed loess-palaeosol record has been obtained here thanks to the position of the sequence on a slope, dissected by a palaeogully. This, as well as the application of sedimentological, palaeopedological (including micromorphology) and palynological methods, makes the sequence an important key to understanding the regional palaeoenvironment during MIS 10.

105The Novyi Tik sequence comprises three sub-sequences, each consisting of a well-developed pedocomplex overlaid by a loess series. Within the pedocomplexes, thin loess beds and cryogenic features are a reflection of relatively short and dry cold events within otherwise warm stages. Within the main loess units, interstadial soils as well as incipient soils occur, also reflecting palaeoclimatic oscillations. The upper part of every pedocomplex was disturbed by solifluction and the formation of soil veins, at the beginning of each stadial. Larger ice-wedge pseudomorphs, found at the top of the sections, formed at the end of MIS 2.

106At the base of the sequence, Pedocomplex III includes a lower Luvisol, formed during an interglacial, and an upper incipient Gleyic Luvic Phaeozem. The Luvisol has the most pronounced features of lessivage in the entire sequence. Podzolization features in the upper Gleyic Luvic Phaeozem indicate a rather high humidity. Nevertheless, the pollen record demonstrates a moderately dry climate at both the beginning and at the end of the interglacial. The Pedocomplex III is correlated with the Upper Zavadivka unit in stratigraphy of Central Ukraine, the Luvisol with the Luck soil of Western Ukraine - both supposedly formed during MIS 9.

107Studies of Pedocomplex II at Novyi Tik have confirmed earlier results (Fedorowicz et al., 2013; Łanczont et al., 2014) and the existence of four phases of soil formation during Korshiv times (MIS 7), which is correlated with the Potyagaylivka pedocomplex in Central Ukraine. A well-pronounced loess unit with pollen of typical cryophytes within this pedocomplex was documented in Western Ukraine firstly. During the early Potyagaylivka times (‘pt¹’), first a Luvisol and then an incipient Luvic Phaeozem formed under an interglacial climate, detected from the pollen data. During the late Potyagaylivka (‘pt³’) times, Chernozem and Cambisol developed under steppe during two successive interstadials, tentatively correlated with 7c and 7a sub-stages, respectively.

108The soil succession and pollen data from Pedocomplex I enables its correlation with the Kaydaky-Pryluky sequence in Central Ukraine, and MIS 5. The redeposition of soils of the Pedocomplex I and the truncation of the Loess II were caused by strong erosion phases. The pedological and palynological evidences of the last interglacial were found in the lower soils of Pedocomplex I (Luvisol and Retisol of the Kaydaky unit). The four upper soils of the pedocomplex, corresponding to the Pryluky unit and formed during interstadials, are tentatively correlated to MIS 5c and 5a. Two cryogenic events within Pedocomplex I reflect strong coolings during the first (MIS 5d = Tyasmyn) and second (MIS 5c = ‘pl²’) Early Glacial stadials. During the cold periods (‘ts’ and ‘pl²’), gully alluvium – with generations of soil veins and frost fissures – accumulated in the palaeodepressions. Higher on the slope, gully alluvium facies turn into thin loess-like sediments.

109High rates of silt accumulation and a decrease in erosion are reflected by the Loess I formation, which formed during the Pleniglacial, particularly during the Late Pleniglacial (Bug period). Three well-developed Gleysols, formed under cold steppe, correspond to Pleniglacial interstadials (supposedly from ‘vt’, ‘df’ and ‘pc²’ times). At least two incipient tundra gleys have been documented within the Bug loess in the sections of the palaeodepression. Gastropods shells have been found in the Bug loess, the ‘pl²’ loess streak and in the oldest loess (correlated with MIS 10).

110The importance of the Novyi Tik site is underlined by the presence of two valuable archaeological artefacts, which are located at different stratigraphic levels. The older one is a Levallois core nucleus, found in the BCs horizon of the Podzol (‘pl^1b1’) tentatively correlated with the beginning of the MIS 5c. The second artefact is a split bone of Mammuthus primigenius, found in the lower part of the Bug loess (MIS 2). Therefore, further archaeological investigation in this area is necessary.

111Studies of the Novyi Tik site have provided new information on short-term development of palaeoenvironment. However, in order to make more reliable correlations with other Ukrainian and European key sections, further studies should involve dating, malacological and archaeological research.