Stratigraphic and tectonic settings of Early Paleolithic of North-West Armenia
Abstract
The Quaternary stratigraphy and tectonic development of the southern Javakheti Upland and the adjacent Upper Akhurian and Lori uplifted basins in NW Armenia (Lesser Caucasus) and geological position of the early and middle Acheulian lithic industries were studied using a multi-method approach. Studies of sedimentary sections, petrological and geochemical correlation of lavas and tuffs, K–Ar dating of volcanic rocks and SIMS 238U–206Pb dating of tuffs, examination of obtained fossils and pollen analysis, and determination of remanent magnetic polarity of volcanic rocks and clastic sediments have been used to compile the stratigraphic scheme and to estimate the age of units.
The low-mountain topography was differentiated to ridges and basins to the beginning of Quaternary. The eruptions of basalts and basaltic andesites evened topography of the Upper Akhurian and Lori basins in the Gelasian. The lava flows spread along big river valleys at tens of kilometers. At the late Gelasian, the eruptions of basaltic trachyandesites, trachyandesites and dacites replaced the basaltic eruptions. The latter dammed the Akhurian River flowing to the south and the upper Akhurian River found the flowing to the east via the valley-like depression of the Karakhach Pass to the Dzoraghet-Debed valley. The course-grained tuffaceous-clastic Karakhach unit was deposited during the Olduvai subchron (not earlier than 1.9–1.85 Ma) and the earliest Calabrian. The water transit between the Upper Akhurian and Lori basins was interrupted later because of rise of the Karakhach Pass. Volcanic activity renewed for a short time in the early Calabrian (∼1.7 and 1.5–1.4 Ma). The end Calabrian and earliest Middle Pleistocene sedimentation (∼1–0.5 Ma) occurred in stagnant water, partly lacustrine conditions. This was expressed by formation of the relatively fine-grained Kurtan unit. During the last ∼0.5 Ma, the region underwent flexure-fault deformation and tectonic uplift at 350–800 m.
The epoch of formation of the Karakhach unit was characterized by middle mountain topography and humid climate. Not later than 1.85 Ma, the region was occupied by the earliest hominines producing lithic industries of the Early Acheulian aspect. They contained crude hand-axes and other macro-tools, made of local dacite and basalt (sites of Karakhach, Muradovo and Agvorik). Early appearance of these industries might be caused by natural parting of dacite and basalt to tabulated fragments that gave a possibility to make such macro-tools. The Middle Acheulian artifacts were found in the Kurtan I section of the Kurtan unit.