Paleohydrogeological and geophysicalresearch aimed at reonstruction of paleoclimate in lake Sevan basin, Armenia

Abstract

In order to determine the natural conditions for the restoration of the paleoclimate of the lake Sevan basin (Armenia) the materials related to the geomorphological-tectonic and paleohydrogeological structure of the inshore and aquatic parts of the lake were analyzed and summarized. Special geophysical studies of the paleohydrogeological orientation have been carried out: the paleohydrogeological zoning of the catchment area has been carried out, data on the structure of its paleorelief have been obtained, a number of paleochannels have been identified, the main routes of concentrated movement and the groundwater discharge area have been determined, including within the lake waters. Data on the section of terrigenous deposits dating of the lake coastal parts were obtained according to paleomagnetic studies The seismic-acoustic wave studies carried out in the water area of the Small Sevan made it possible to draw up geophysical sections characterizing the structural features of the lake’s bottom sediments. In general, the obtained data will be used to determine the age of the limnological deposits of the inshore and bottom parts of the lake, to establish the paleohydrogeological, geoecological, and paleogeographic features of its development in the Holocene in connection with an attempt to reconstruct the paleoclimate of the studied region. According to the bathymetric data, the bottom of the Greater Sevan represents a flat plain with fluctuations of depths on average 40 ÷ 51.5 m. In the south-western part of the territory, north of the village of Getashen, erosion troughs that are associated with the ancient valley of the river of Argichi are traced. The existence of the latter is also confirmed by geophysical data. It is assumed that the morphology of the deep part of the Small Sevan bottom reflects the presence of significant tectonic subsidence here. At the same time, on the south-western and western slopes, in the formation of the present-day relief of the bottom of the lake, the main role was played by outpourings of Holocene-age lavas. In the northeastern coastal part of the Small Sevan, to a depth of 70 ÷ 99 m, closed depressions have been established, the origin of which is explained by local tectonic subsidence. In general, the bottom relief of the Small Sevan differs significantly from the Greater Sevan, both in terms of complexity and origin.