Local neotectonic restructuring in the North Caucasus orogene

Abstract

Cases of regional neotectonic restructuring are well known in the Caucasus. Detailed geotectonic zoning and identification of local structural changes are required for the engineering geological and paleoecological studies. The Baksan River valley was studied in the North Caucasus as an example of such a restructuring. The problem about the number of Quaternary volcanogenic strata and their role in structural rearrangement is considered. The Pliocene – Plio-Pleistocene volcanogenic strata cloak-like covered the Nizhnechegemsky district before the first reconstruction. Zayuksky graben (with an amplitude of 200 m) was formed in the end of Plio-Pleistocene; and a part of Pliocene- Plio-Pleistocene volcanogenic strata sank into it. Two layers with a total thickness of more than 100 m were deposited in the resulting trough. The upper strata (baxangess) contain redeposited boulder-pebbly volcanogenic material. Colluvial, subaquatic-deltoid and lacustrian facies are registered. The orographic depression in Zayuksky graben was completely filled before Eopleistocene as a result of next restructuring. The Baksan River began to form a wide well-terraced valley without any significant left tributaries there. The baxangess strata contain pebble of liparite lavas and obsidians. This pebble was used by the Paleolithic man for making stone tools. Poor roundness of pebble indicates its short transportation distance. Contradictory ideas about the initial distribution of parental volcanic rocks are considered. It is concluded on the acuteness of identifying such neotectonic rearrangements for the analysis of various paleogeographic and paleoecological changes.