LOESSFEST'09 | Aug. 31st – Sept. 3rd, 2009 |Novi Sad-Serbia
Loess-Paleosol and Pollen Succession from the Donets Area (Eastern Ukraine)
Gerasimenko, N.1
1Earth Sciences and Geomorphology Department, National Taras, Shevchenko University of Kyiv, Glushkova str., 2, DSP 680, Kyiv, Ukraine;
The Donets Area is presently located in steppe, though its northern part is transitional to forest-steppe. Lithological study of seven loess-paleosol sections (humus and CaCO3, grainsize and bulk chemical analyses), as well as pollen study of the sections Novoraysky, Novotroitsky, Bantyshevo, Kryva Luka and Amvrosievka demonstrate an alternation of different paleoenvironments during the Middle and Late Pleistocene. The Quaternary framework of Ukraine (Vekitch et al., 1993) is used for stratification of the sections.
The Martonosha unit is the first pedocomplex above the Brunhes-Matuyama boundary. All Martonosha soils are strongly enriched in Al2O3, Fe2O3 and clay. The lowest red-brown soil was formed under warm-temperate forest which includes pine, broad-leaved trees and small admixture of diverse Neogene relics. The middle red-cinnamonic soil developed under sparse oak-pine forest with Pinus subgen Haploxylon and Neogene relics. It is separated by loess bed from the uppermost brown soil formed under temperate mixed forest. The Sula unit is the thick loess connected with formation of deep and widely open frost wedges. At the beginning of the Sula time, grassland occupied plateau and birch-pine groves occurred in gullies. Few oak and lime possibly survived on the southern slopes. Later on, more xeric components (Artemisia and Chenopodiaceae) expanded, and woods consisted of pine only. The Lubny unit includes two pedocomplexes (each of them consisting of the lower grey forest soil and the upper thick chernozem), separated by loess bed. The Lubny soils are less rich in Al2O3, Fe2O3 and clay than the Martonosha ones. The lowest soil was formed under forest: firstly boreal one, then Quercetum mixtum (though with few Juglans), and finally Carpinus appeared. The lower chernozem, always leached of carbonates, developed under forest- steppe. During the accumulation of loess bed between the two pedocomplexes, two generations of ground wedges were formed, and grassland was replaced by xeric steppe. The Upper Lubny grey forest soil developed under Quercetum mixtum in forest-steppe landscapes, and the Upper Lubny chernozem was formed under mesophytic steppe (forbs and grasses). Thus, the climate of the Lower Lubny sub-unit was wetter than during the Upper Lubny sub-unit. The Tiligul unit is the thick loess, formed in treeless grassland. Frost wedges are open, in a raw, from its bottom.
The Zavadivka unit consists of two sub-units, separated by the thin loess. The Lower Zavadivka sub-unit, represented by reddish-brown soils and leached chernozems, was formed in warm-temperate forest-steppe. The woods included Quercus, Ulmus, Tilia, and, later on, Carpinus and few Neogene relics. The steppe was mesophytic. This time is correlated with the Holsteinian interglacial (after the last Pterocarya appearance). The Upper Zavadivka subunit includes brown and cinnamon-brown soils, formed under mixed forest and mesophytic bushy steppe. Frost wedges open, in a raw, from the bottom of the loess unit, separating the two Zavadivka sub-units. The Oril’ unit is the whitish-pale loess, strongly enriched in carbonates. Xeric steppe existed during its accumulation (only few Pinus occurred in valleys). The Potyagaylivka unit is represented by chernozems and brown rendzinas, both less thick than the above-described soils, and both with the characteristic forms of carbonates. They developed under forest-steppe of temperate climate. From the beginning to the end of the unit, mesophytic steppe was replaced by grassland, and the mixed forest was changed by pine wood. Thus, the climate became drier. The Dnieper unit, correlated with Saalian, is the thick loess which includes two incipient soils at the base. Cryogenic structures of the Dnieper time are diverse: wedges (up to 3 m deep), fissures, lamination and heaving. Plateau was covered by xeric steppe, but, in depressions, Pinus and Betula (including shrub Betula) grew, and, at the beginning of the unit, few Rhamnus and Malaceae occurred.
The Kaydaky unit includes a succession of luvisol, grey forest soil and chernozem. Sometimes the luvisol is underlain by incipient chernozem, and the upper chernozem is overlain by humic hillwash. The incipient chernozem was formed under boreal steppe, and the other soils developed in forest-steppe of temperate climate. During the luvisol formation, a role of broadleaved trees was the highest one, and early-temperate Quercetum mixtum phase was replaced by late-temperate phase (with Carpinus appearance) of an interglacial. During the upper chernozem formation, a role of broadleaved trees gradually became smaller, marking a transition to south-boreal and boreal environments. The Kaydaky unit is correlated with the Eemian, as it has been earlier suggested for the Central Ukraine (Roussaeu et al., 2001). The Kaydaky chernozem includes the earliest Mousterian findings (Gerasimenko, Kolesnik, 1992). The Tyasmyn unit is the thin loess formed in xeric steppe, though some Pinus, Betula, Alnus, Salix grew in valleys, and, at the beginning of the unit, few Quercus occurred. Two generations of cryogenic features developed during this time. The Pryluky unit consists of two soil sub units, separated by thin loess. Each of the sub-units includes the lower cambisol and the upper chernozem (or kashtanozem in the south of the area). The cambisols were formed in forest-steppe of south-boreal climate (few broad-leaved trees grew). Chernozems and kashtanozems developed under grassland and xeric steppe, correspondingly. Absence of pollen of broadleaved trees in the upper chernozems and kashtanozems indicates that the climate became cooler to the end of the Pryluky soil formation. The loess, separating the two soil sub-units (TL 95±6 ky BP), was firstly formed under grassland (few Tilia in gullies), and then under xeric treeless steppe. The Pryluky soils are correlated with the Early Glacial interstadials, and the Tyasmyn and inter- Pryluky loesses correspond to the Early Glacial stadials. Mousterian cultures existed in the area during these times.
Th e Uday unit is the very calcareous loess (75±4 ky BP) connected with formation of deep frost wedges. Humus content in the Uday loess is somewhat higher than in the other loesses that might indicates slower sedimentation rates. Plateau was covered by xeric steppe, but Pinus, Betula, Alnus, Rhamnus and Malaceae grew in valleys, and the Mousterian sites occurred on terraces. The Vytachiv unit is a set of three brown rendzinas, separated by thin loess layers. This unit (36,0±3,0, 57,5±13,0 ky BP) is related to the Middle Pleniglacial. The two lower soils were formed in south-boreal environment – mesophytic steppe and Betula-Pinus forest (few Quercus and Ulmus). The upper soil developed under steppe (forbs and grasses), though some woods obviously occurred in valleys. During formation of loess interlayers in the Vytachiv unit, treeless grassland existed, and the underlying soils were densely dissected by thin long fissures. The Bug unit is the thick loess (25,5±2,0 ky BP), corresponding to the first half of the Late Pleniglacial. Several incipient soils occur in its lower part. During the first half of the unit, grassland occupied plateau, and some Pinus, Betula, Alnus and Salix grew in valleys. Later on, only xeric treeless steppe existed. Cryoturbations of the Bug time are similar to those of the inter-Vytachiv loess units. The Dofinivka unit is a couplet of incipient soils (17,0±3,0, 15,5±3,0 ky BP), separated by thin loess. The soils of light-brown colour are not strongly distinguished from loesses by the contents of humus, Al2O3, Fe2O3 and clay, but they are rich in carbonates (frequently also in gypsum). Dry steppe existed on plateau, though mesophytic herbs and boreal trees grew in gullies. The Upper Paleolithic sites connected with the Dofinivka unit, are dated around 18 ky BP (Krotova, 1996). The Prychernomorsk unit is the loess, separated into two parts by the Late Glacial incipient soils (13,5±2,0, 11,4±1,4 yr BP). The lower loess was formed under dry steppe, and the upper loess was accumulated under grassland. Shrub Betula grew in gullies since the Dofinivka times. Boreal forest-steppe existed during the Late Glacial interstadials.