Nowdays series of mesolithic and neolithic peat sites are discovered at 6 peat bogs on Upper Volga: Dubna (Moscow region), Ivanovskoye and Berendeevo (Yaroslavl region), Sakhtysh and Podozerskoye (Ivanovo region), Ozerki (Tver region). The last is situated at 20 km to the south from Tver, in the basin of river Shosha, right tributary of Volga. More, than 20 mesolithic and neolithic sites were discovered there in 1990-1991 by M.G. Zhilin and N.V. Levina.

In early Holocene territory of the future peat bog was occupied by a lake system, drained by river Inyuha, left tributary of Shosha. Pollen analisys, carried out by E.A. Spiridonova, showed, that sedimentation of peat began already in Preboreal. Several transgressions and regressions during first half of the Holocene caused changes of the shoreline, which is reflected in site situation. The site Ozerki 14, one of the earliest there, occupies the top of a sandy island, surrounded by peat, in the middle of the former lake system. It is not excavated yet, but small sounding showed such stratigraphy: 1 - modern soil, thickness - 5 cm; 2 - grey sand - 10 cm; 3 - orange sand - 20 cm; 4 - pale yellow sand - 14 cm; 5 - grey spotty sand (ancient soil) - 15 cm, 6 - pale sand with iron oxyd. Flint artefacts were found in layers 3-5, mostly in layer 5, among them flakes, blades, fragment of a subconical core, endscraper and a tanged point, made of irregular blade. Stratigraphy and finds are typical of early period of Butovo culture. Connection of the site with the highest level in the lake system supports its early, probably, Preboreal, dating.

The next stage is represented by sites Ozerki 16 and 17, situated in 600 m to the west from this island. They were occupied during deep regression, so their cultural layers are blanketed by 1,8-2,5 m of peat (before peat mining started it was about 5 m). 12 square metres are excavated at Ozerki 16. Stratigraphy is: 1 - pale brown peat, thickness 6-22 cm; 2 - dark brown peat with wood - 0-32 cm; 3 - brown-yellow peat - 26-84 cm, 4 - a streak of hyttia with shell - 2-4 cm; 5 - brown peat with mall admixture of hyttia with shell - 4-20 cm; 6 - dirty yellow hyttia with small quantity of shell - 2-14 cm; 7 - brown peat with admixture of sand, wood branches and rubbish, charcoal and long splinters of worked pine wood, used for making creels (conical fishing traps) - we call it "creel splinters"- 0- 16 cm; 8 - grey clay with peat - 0-15 cm; 9 - bluish-grey clay (lake bottom). The site has two cultural layers. The upper coinsides with layer 4, it contained several flint flakes, bones and a fragment of early neolithic pottery of Upper Volga culture. The lower cultural layer occupies layer 7, some flints and bones, belonging to it were found in upper part of layer 8. An oval-shaped float with a hole at one end, made of pine bark, met in layer 6 probably also belongs to it. Ends of poles, sharpened with flint axe, were driven into lake bottom from this layer. Finds include flint flakes, blades and tools: endscraper, scraper-knife on blade, tanged point, made of blade, with traces of black resin (birch pitch) on the tang. A sinker, made of a limestone pebble with concave edges, tied by a bog plant, was found. Bone tools are represented by long arrowhead with biconical head, even longer arrowhead with double biconical head, a point of a spearhead and a fragment of a burin-side scraper, made of beaver'incisor. Small fragment of a wooden barbed point supplement the collection. A C-14 dating - 8770+-40 B.P. (GIN-6654) was obtained from splinters of worked wood from this layer. Pollen analisys dates the upper layer to early Atlantic, and the lower layer - to the first half of the Boreal (approximately 8800 - 8600 B.P.). Forests of the taiga type with dominance of birch played leading role in the landscape. Bones of elk and beaver are most numerous, marten, mice, birds and fish are also present. Shells of haselnuts and seeds of water lilies were found in the cultural layer (the latter also in human excrements). The site was occupied, most probably, in late summer-early autumn by the population of the second period of Butovo culture.

The site Ozerki 17 is much similar. It is situated at 100 m to the north. 41 square metre was excavated there. Stratigraphy is the following: 1 - brown peat, thickness - 50 cm; 2 - pale yellow peat - 0-68 cm; 3 - pale brown peat - 34-134 cm; 4 - pale yellow peat - 0-40 cm; 5 - forest rubbish (splinters of branches, bark, leaves etc.) with brown peat (5a - more rubbish, 5b - more peat - 0-72 cm; 6 - dark brown peat with admixture of sand, charcoal, creel splinters - 0-20 cm; 7 - grey sand with peat - 0-18 cm; 8 - bluish-grey sand with clay - lake bottom. In the southern part of excavated ground some more layers were met: 9 - pale yellow peat - 0-10 cm, underlies layer 5; 10 - dirty-yellow hyttia, - 0-20 cm underlies layer 9; 11 - greyish-brown hyttia with small shells - 0-30 cm, replaces layer 6 and underlies layer 10; 12 - a lense of forest rubbish with admixture of sand and brownish-black peat - 0-12 cm, lies between layers 5 and 9. In the northern part of excavation pit a streak of yellow sand 1-2 cm thick was met in the upper part of layer 6, or between layers 5 and 7, it was named layer 13.

4 cultural layers were traced. The first (upper) is met in the lower part of layer 5a and contains some bones and flint flakes and two fragments of middle neolithic pit-and-comb pottery. The second layer lies in the lower part of the layer 5b, a number of bones, mainly, birds', a bone point, flint flakes and fragments of comb pottery, transitional fron early to middle Neolithic, were found there. The third cultural layer coinsides with the lense of layer 12. It produced numerous birds' and some other bones, flint knife and some flakes, bone figured and blunt arrowheads, a pine bark float with a hole at one end, a sinker, made of pebble with traces of binding, and several sherds of the early neolithic Upper Volga culture. This layer is dated by pollen to early Atlantic.

The forth, lower layer, is connected with layers 6,11,13 and the upper part of layer 7. The layer 6 was sedimented at the site, while layer 11 is its train. Layer 13 is washed layer 6, from which particles of peat were carried away, and finds in layer 7 appeared, mainly, as a result of trampling and sinking. Many ends of poles, sharpened with flint axe were driven from this cultural layer into underliying layers. Finds include willow-leaf shaped and tanged swiderian and postswiderian arrowheads, made of blades; microblade inset, burin, microendscraper, obliquily retouched point, perforator, fragment of woodcutting tool, half-finished subconical core, blades and flakes. A series of sinkers - pebbles with concave edges, and without any secondary trimming, tied across with bog grass was found. One piece of limestone had a natural hole, in which fragment of twisted rope 5 mm in diameter was still preserved. Among other fishing implements are fragments of a net and pine bark oval perforated sinker. Bone tools include needle-like, with biconical head, and blunt arrowheads, fragments of spearheads, intact small fishinghook with remains of a line 1 mm thick on its butt end, an "ice-pick", burin-scrapers made of beaver' incisors, fragments of knives and other tools, pendants of beaver' and elk' incisors, perforated disk. This inventory is characteristic of the second period of Butovo culture.

A C-14 dating 8830+-40 B.P. (GIN-6655) was obtained from splinters of worked wood, collected in the concentration of finds. Pollen analysis dates this layer to the first half of the Boreal (about 8800-8600 B.P.). Faunal remains show the same picture, as in Ozerki 16, only fish bones, among which pike dominates, are more numerous, than all the rest. Shells of hazelnuts and seeds of yellow water lily were met. This site was also occupied during late summer - early autumn. Fishing, supplemented by hunting and food gathering was the economic basis of its inhabitants.

The next group of sites (Ozerki 4, 9-13) is connected with the transgressive phase of the lake system. They occupy small islets, buried under pear and uncovered during peat mining. Their cultural layers lie in semi-clay ancient soil, formation of which began during previous deep regression. 8 square metres were excavated in the train of Ozerki 9. Worked bone and elk' antler, prismatic and pencil-like cores for producing regular microblades, fragments of creel splinters were found in a thin streak of brown peat with forest rubbish, lieyng on bluish-grey clay - the lake bottom. A sample of this peat gave a C-14 dating 8050+-450 B.P. Flint flakes, blades and tools: endscrapers, burins, insets and other implements, typical of late phase of Butovo culture were collected from surface of these sites.

One of the most interesting and rich settlements, Ozerki 5, emerged during the next regressive phase. It is situated near Ozerki 17, at 650 m from the sandy island with the site Ozerki 14. 94 square metres were excavated in 1990-1992. Stratigraphy is the following: 1 - dark brown peat, thickness 18-50 cm; 2 - brownish-black peat with admixture of sand, wood and forest rubbish - 15-30 cm; 2/3 - contact of layers - spotty brown and black peat - 5-15 cm; 3a - brown peat with admixture of sand and small amount of forest rubbish - 10-25 cm; 3b - pale brown peat with large amount of reed-mace leaves - 1 m; 4 - grey carbonised hittia - 30 cm; 5 - grey sand mixed with hyttia - 12 cm; 6 - bluish-grey sand - lake bottom.

Four cultural layers were traced: the first, upper, is met in central and western part of excavated ground in layer 1, severely destroyed during peat-mining (about 3 m of peat was taken away). Several bones, flint flakes and fragments of middle neolithic pit-and-comb pottery were found there. The second cultural layer was also met only in the central and western part of excavation pit. It lies in layer 2 (in eastern part this layer contains no finds). Traces of fireplaces and clusters of finds were discovered there, among them numerous flint flakes and rare blades, cores and a plenty of stone tools: scrapers of different types, rare burins, concave scrapers, perforators, borers, knives, wood-cutting and combined tools. Arrowheads include postswiderian tanged points together with willow-leaf shaped points with flat retouch on both sides. A darthead with flat retouch, covering the whole dorsal and a part of ventral face was found. Scarse bone tools include a one-sided barbed point, fragments of arrowheads, burin-scrapers of beaver' incisors, awls, pendants, fragments of antler wood-cutting tools. Comb pottery with ground granite, transitional from early to middle Neolithic was met in the upper part of this layer, together with comb pottery of the late period of the early neolithic Upper Volga culture. The lower part of this layer produced comb pottery with sand and organic admixture of the second half of the Upper Volga culture. Elk and beaver dominate among mammals' remains, fish and birds' bones also numerous.

The third cultural layer was met in the eastern part of excavated ground, where the second cultural layer was absent. It is connected with the contact of layers 2/3, and at the eastern end with the uppest part of layer 3a, overlieing the IV cultural layer without any sterile streak. Several clusters of finds were discovered. Pottery was made with admixture of ground sherds and some organic, ornamented with shallow imprints, typical of early period of the Upper Volga culture. Lithic artefacts include flakes, blades, cores, scrapers of various types, burins on broken blades and flakes, knives, insets with sharpened edges, concave scrapers, wood-cutting and combined tools. Bone artefacts are represented by biconical, figured and one-winged with a barb arrowheads, awls, fragments of antler axes and adzes, burin-scrapers of beaver' incisors, pendants of beaver and elk teeth. Especially interesting is a wooden dart 1,7 m long with a small biconical head. Faunal remains show dominance of elk and beaver, badger also present, together with numerous birds and fish.

Disappearence of black spots, emergence of sand and calcinated bone powder indicates the IV, lower cultural layer. Number of finds rapidly increases, pottery disappeares. Remains of fireplaces and well-preserved pits, one with a sheet of birch bark at its bottom, we re discovered there. Among lithic artefacts flakes are especially numerous, blades also met, accompanied by cores for their production. More than 500 tools were found, scrapers of various types prevail. Burins on broken blades and flakes are less numerous. Most part of insets is composed by bladelets with sharpened edges, backed bladelets are very rare. Oblique and symmetric points were made of blades. More than 50 arrowheads, made of blades, were found, among them willow-leaf shaped prevail. They are usually trimmed with flat retouch of the point and base, but some bear such retouch over the whole perimeter. Tanged points also compose an important series. Knives, made of blades and flakes, concave scrapers, perforators, borers, combined tools, hammerstones and abrasive slabs, core and polished axes, adzes and chisels are plenty. Some blades are partly wrapped by birch bark, and some sinkers - pebbles, bear traces of binding with bog grass.

Bone and antler artefacts are numerous (more, than 500, including fragments) and various. Arrowheads are represented by needle-like, with biconical head, with flat broad head, one- and two-winged with a barb, blunt. Other tools include barbed points, harpoons, fishing hooks, daggers with straight and oblique blade, different knives, scrapers, awls, punch and pressure-flakers, senew straigtheners, burins and burin-scrapers of beaver, fox and wild boar' teeth, different pendants of animal teeth, splinters of bone and fragments of bone tools. Many bone artifacts are ornamented with simple, or more complicated designs. Especially interesting are fragments of ornamented pebbles, intentionally broken and burned afterwards, resembling australian "churingas". Bones of elk and beaver dominate among faunal remains. Red deer, roe deer, wild pig, badger, hare, marten, otter, wolf, fox, mice, numerous birds and fish are also met. Shells of haselnut and waternut, seeds of yellow water lily indicate, that the site was inhabited in summer-early autumn. Lithic and bone artifacts aretypical of the final stage of Butowo culture.

Several C-14 datings were obtained for this layer: 7410+-150 (GIN-7216 - charcoal), 7190+-180 (GIN-6659 - charcoal), 7120+-50 (GIN-7217 - worked log), 6970+-120 (GIN-6662 splinters of worked wood). Pollen dating of peat, containing this cultural layer is transition from Boreal to Atlantic and early Atlantic. The III cultural layer is dated to the first half of Atlantic by pollen, and the II cultural layer - to the end of the first half of this period. The lower part of this layer produced a C-14 dating 6450+-160 B.P. (GIN - 7215 - splinters of worked wood), and a worked log from its roof was dated to 5930+-200 B.P. (GIN-6663).

In early Holocene territory of the Ozerki peat bog was occupied by a lake system. Since early Mesolithic in was inhabited by the population of the Butovo culture, which lived there for several milleniums. Succesful adaptation of this population to environmental canges during Holocene is reflected in lithic and bone inventory, economy and setlement system. During Mesolithic and the first half of the Neolithic sites were closely tied to shorelines, and changed their place in accordance with regressions and transgressions.

By 7000 B.P. development of the Butovo culture terminated with transition to Neolithic, marked by emergence of the Upper Volga culture, genetically linked with the former. The latter is represented by two periods, and existed there for another millenium. About 6000 B.P. another tradition of comb pottery, characteristic of North-West of Eastern Europe appeares. Population of this tradition mixed with inhabitants of final Upper Volga culture, which led to formation of the Lyalovo culture with pit-and-comb potery and beginning of the middle Neolithic.