extended abstracts - Geomorphic Processes and Geoarchaeology

Geomorphic processes and geoarchaeology
development of peat-bogs in depressions [2]. Younger phase of fluvial deposition falls on
the period 3300-3100 BP [3, 4].
The Roman Period in southern Poland (1-3 rd centuries AD) was a time of
enhanced human activity and flood deposition, which is proved by subfossil stumps and
tree trunks processed by man in the channel alluvia of the Vistula [5] and the San [6] river
valleys, as well as fans of small valleys in the Carpathian margin [2]. In the Migration
Period (5-6 th centuries) regression of agriculture, reforestation and simultaneous increase
in frequency of floods (growth of precipitation) is observed [7, 8]. This phase is recorded
by agglomeration of tree trunks in the channel alluvia of the Vistula [5], Wisłoka [9] and
the San [6] river valleys. This time is also represented by insert of the alluvia within the
Strvyaž terrace in Ukrainian Carpathian foreland [10].
The 8-10 th centuries are attributed by the colonisation of river valley bottoms, the
earliest in the Morava river valley [11]. Correlation of sequences of fluvial, slope and
peat-bog sediments in the Carpathian river valleys indicates that in the 10-12 th centuries
expansion of human settlements took place in the catchment of the Upper Vistula river. In
the Wisłoka river valley migration of meandering channels started about 965 ± 75 BP
(940-1240 cal AD) [12]. Similar dates: 925 ± 30 BP (1030-1180 cal AD) and
1080 ± 30 BP (890-1020 cal AD) were obtained from subfossil tree trunks in the
Wislok valley [13].
The progressing deforestation in the 10-12 th centuries is evidenced by
palynological analyses of overbank sediments of the Wisłoka river valley dated at
1040 ± 95 BP [12], as well as peat-bogs and organic sediments overlain by overbank
sediments in the Upper Dniester Basin [14]. Record of the Early Medieval floods is
reflected in the Dniester river valley, in its Carpathian outlet, by insert of 2-4 m
gravel terrace [15].
The tree felling, overbank deposition and displacements of river channel in the
Vistula river valley indicate frequent floods in the period 900-1150 AD [12, 7, 3]. In the
same time, in the Beskid Śląski Mts. foothill, aggradation of the Upper Vistula alluvial
fan began [16]. Simultaneous aggradation in the Lower Strvyaž river valley [10].
Coincided with increase in precipitation and cooling in the first half of 11 th century.
Covering of peat-bogs by overbank sediments, dated at 620 ± 110 BP (1160-1490
cal AD) and 650 ± 75 BP (1220-1430 cal AD) in the Upper and Middle Dniester
valley [15] indicates increase in frequency and violence of floods in 14-15 th centuries,
which could have been connected with deforestation and increasing precipitation [17]. It
is correlated with dated by dendrochronological method sequence of tree trunks fallen or
cut during the floods in the 14 th century in Starunia in the Velyky Lukavets river valley in
the Ukrainian Carpathians [18]. The phase of floods in the 14-15 th centuries is confirmed
also by tree trunks dated at 650 ± 40 BP and 660 ± 45 BP (1270-1400 cal. AD) buried in
alluvia of the Michydra and Moldova rivers (tributaries of Siret) in Bukovyna region [15,
19]. Similarly, single tree trunks from the 14-15 th centuries were found in the Vistula [5,
7] and the San [15] river valleys.
In the 15-16 th century agriculture stretched on upland and mountainous areas.
Deforested terrain was exposed to soil erosion. Colonisation of the San catchment area in
the Bieszczady Mts. in the transition of the 15-16 th centuries, was directly reflected by
soil erosion and deposition of flood sediments, both in small valleys (460 ± 50 BP) [20],
and in the San river valley [20, 21]. The scale of flow oscillation and rate of overbank
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