extended abstracts - Geomorphic Processes and Geoarchaeology

Geomorphic processes and geoarchaeology
was S. Vainstein who referred its construction to the 3 rd Uigur Khaganate and dated it
using indirect sources to 750 AD [2]. Both researchers stressed the specific island
location of the monument and proposed hypothesis of its initial construction on land. This
proposal was based on logical implications and on local folklore that contains repeated
indications of the young age of Lake Tere-Khol. No direct geomorphological data had
existed in favor or against of this opinion till last years, though the question whether the
fortress had a connection with land at the time of its construction is important for
interpretation of the monument, especially because of negligible signs of its occupation
found during excavations in 2007-2008 [3, 4]. Excavations were a core part of the rescue
project organized in view of potential risk for the monument imposed by destruction of
island banks and fast approaching of the coast line to the fortress walls.
Figure 1. Por-Bajin Fortress (ca 750 AD) in the Tere-Khol Lake
Along with archaeologists a group of scientists was working at the fortress. One of
the aims of scientific research was reconstruction of the history of the Tere-Khol Lake
and the Island of Por-Bajin. The three study objects may make different successions in
their formation: the lake may either older or younger than the fortress, the island may be
either older or younger than the lake, and in any case the island (or the initial hill) is older
than the fortress. Initial scenarios taken into consideration were as follows:
(1) «young lake – old island»: fortress was built on a hill which was later isolated
by transgression of the lake – scenario [1, 2];
(2) «old lake – young island»: the island appeared in an existing lake;
(3) «old lake – old island»: the island was a hill in a dry land that was later
inundated by the lake and only after that the fortress was built.
Preliminary bathymetrical survey revealed that in spite of its rather large area
(33 km²) the lake is very shallow: average depth is 0.5 m, maximum depth – 1.2 m with
single hollows down to 1.9 m. The lake has mostly underground water supply and is
213