The Paleolithic cave of Qaleh Kord (Qazvin, IRAN): geoarchaeological study by using micromorphology and physical-chemical analysis

The Qaleh Kord cave is a Paleolithic site located near Qaleh village, some ۱۱۵km west of the city of Qazvinin the western part of the Qazvin Province of Iran. The bulk of archeological materials were unearthed fromtwo major excavation trenches close to the mouth of the cave and a third excavation trench inside a lateralchamber less than ۳۰ meters from the main entrance of the cave. Initial geological investigations on thesediments near the entrance of the cave, revealed a very high frequency of anthropogenic components (notecofacts) occurring during the initial post-depositional formation of almost the entirety of deposit. Methodsimplemented for acquirement of sedimentological data involved general stratigraphy, grain-size analysisand micromorphology, in combination with a series of physical-chemical analyses. Field recordingsestablish the existence of at least two major sedimentological sequences. The upper sequence (Holocene)represents a structurally granular to massive mixture of pedogenized beds of silt-sized sediments withepisodical occurrence of gravelly erosional surfaces and local calcareous flat stones. The lower sequencewhich consists of the much older (Pleistocene?) units is distinguishable from sequence I by the upper-limitwhich in both sections is marked by coarser and more numerous calcic clasts. However, the limit of themajor sequences is for the most part a paraconformity and hard to laterally follow, however structural (andmicro-structural) variations are more readily detectable in the lab results. The grain-size distribution showsa general dominance of the silt (۲ – ۵۰ μm) and fine sand (۵۰ – ۲۰۰ μm) fractions. Overall, the grain sizecurves exhibit a homogenous distribution. The clay fraction makes up less than ۸ percent of the sedimentsin the entire setting and displays only small noticeable rises at the sequential boundary layers.Micromorphology, however, pictures a much clearer shift between the older sequence and the youngsequence. For instance, in the old sequence of the cave deposits, the main components of the ground massare micritic calcite (ash) and vegetal remains; and limestone pebbles and granules make up the coarsefraction and most of them contain Oligo-Miocene fossils which indicates spalling of the cave’s walls as themain formation process of the cryoclasts during predominantly colder and dryer episodes. Whereas theyounger (or Holocene) sequence is characterized by a grey color and by superimposed ash layers, togetherwith limestone boulders, and, locally, chaotic mixtures of geogenic sediments, spherulite and charcoalcontaining sediment (i.e. shepherd deposits), pots, and ash remains. Microscopic observations establishsilt-sized micritic ash as the main component of the ground mass which explains the global dominance ofthe silt fraction in the entire record. Anthropogenic sedimentation remains a constant site forming factorfor the both young and old sequences. Intensification of cryoturbation caused by colder winters probablyled to the increase in coarse fraction in the old sequence. Given the lateral stratigraphic discontinuities andparaconformity between units of the major sequences of Qaleh Kord cave deposits, in the future further indepthanalyses (for instance, magnetic susceptibility evaluation, further micromorphological samplings,etc.) can help to fill our current gaps of knowledge with regards to the determination of the stratigraphicboundaries and correlation of units of the different sections.