extended abstracts - Geomorphic Processes and Geoarchaeology

Geomorphic processes and geoarchaeology
OSL dates have given different results, of which the date 9.9 ± 0.8 ka correlates well with
the 14 C date. These loams cover the terrace surface and continue down the terrace edge
below the low water level of the modern river [4]. This means that the river was incised
by > 1 m in the beginning of Holocene relative to the present.
In the right part of valley bottom a terrace level similar to terrace T0b is found
where the Avdeevo Upper Paleolithic site is located. The site is situated on a gentle hill
with the top at 7 m above the Seim River and 3 m above the Rogozna River low water
level, only a little above the present level of inundation. Core section in the vicinity of the
archaeological site opened two principal units. The upper unit (0-120 cm) consists of
organic-rich loams, which according pollen data accumulated since the Boreal period of
the Holocene. Sharp kind of contact with the lower unit evidence existence of
sedimentation break. The lower unit (opened down to 200 cm) consisted of two 250-35cm
layers of brown loamy sands divided by a 20- cm layer of massive loam. Pollen
content in the middle loam layer is very low, while in both layers of loamy sands it is
high enough to identify steppe or forested steppe communities with participation of
broad-leaf trees (in the upper sand layer) evidencing conditions similar to
modern climate.
Figure 2. Topographic profile across the Seim river valley and lithological sections of
terraces. Symbols: 1 – aeolian sands, 2 – deluvial loam, 3 – alluvial sands, 4 – alluvial
clay and loam, 5 – the main stratigraphic boundaries, 6 – location of sampling, 7 – OSL
date (cal. ka) 8 – 14 C date (uncalibrated 14 C ka), 9 – three periods of Avdeevo site
settlement (uncalibrated 14 C years), according to [2]
Terrace level T0a (h=5-6 m) is widespread at the right bank of the Seim River
between its modern channel and the Avdeevo site (fig. 1). Composition of this terrace
was studied at river bank exposure (section ML-3). The whole section consists of loams
with indistinct stratification interpreted as overbank alluvium. Content of fine sand
increases at depths 0-0.4 and 3.3-4.6 m. OSL dating gave ages immediately following
LGM: between 17.5-20 ka at depth of 2.0 m and between 18.5-21 ka at depth of 4.4 m.
Sandy channel alluvium was reached by hand coring at depth of 3 m below the current
low water level (9 m below the surface of the terrace). Therefore straight after LGM the
river channel was still incised 3-4 m deeper relative to the modern river.
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