Carbonate features in the uppermost layers of Quaternary deposits, Northern Armenia, and their significance for paleoenvironmental reconstruction

摘要

Recent archaeological studies in the Lori Depression of Armenia (Lesser Caucasus) revealed a series of multilevel Early Paleolithic (Acheulian) sites belonging to the Early-Middle Pleistocene stage of occupation of the Caucasus. In the uppermost layers of these sites, the paleosols and sediments contain carbonate features (CFs) whereas the lower layers are absolutely free from carbonates. The aim of this work is to examine the role of detected CFs as an indicator for reconstructions of the Early-Middle Pleistocene paleoenvironments, to determine the source, time and conditions of carbonates' accumulation in initially non-calcareous and high-degree weathered humid paleosols. Three sections were studied: Kurtan I, points 1-2 and Muradovo. There are different forms of CFs represented by the calcified root cells in the layer 1, the hard nodules in the layer 2 and the laminae-like carbonates in the layer 3 of the sites studied. All the CFs are of the aqueous (hydrogenic) origin. The CFs of the uppermost layers 1 and 2 in the Kurtan I, point 2 were accumulated in the Holocene lake. The calcified root cells were formed on the swamp shore whereas the hard nodules on the lake bottom under stagnant water. The laminae like carbonates in the layer 3 were accumulated in the Kurtan I and Muradovo sections due to strong erosion cycle(s) in the Late Pleistocene interglacial period(s) that led to the limestone scour in the region by ground and surface water. They reflect the earliest stage of the allochthonous carbonate accumulation in the area dated by radiocarbon method to approximately 20 ka cal BR Therefore, all the CFs cannot be regarded as indicative of Early and Middle Pleistocene environmental changes, as they appeared in the uppermost layers of the studied sections much later than the time of formation for the surrounding groundmass. (C) 2015 Elsevier Ltd and INQUA. All rights reserved.