Using of microvertebrate remains in reconstruction of late quaternary (Holocene) paleoclimate, Eastern Iran

Study of quaternary microvertebrate remains in eastern Iran, according to a few of the sediments is very important. Reconstruction of quaternary climate in many parts of West and North West of Iran as the biggest karst state is possible, such as cave Kani Mikaiel (Hashemi et al. 2005, 2006, 2007a;b, 2008; 2010, Jangjoo et al. 2010), Yafteh cave (Otte et al. 2007, Hashemi et al. 2015). However, such studies were very poor in eastern and north-eastern Iran (Hashemi and darvish 2006; Hashemi et al. 2008, 2015). Investigation of taxonomic identification; quantification and distribution of micromammals revealed that these remains are useful in paleontology and archaeological research, because their abundance is useful for paleobiostratigraphy and dating of continental sediments. The recent research is about reconstruction of paleoclimate in two archeological sites of Konar sandal (KS) (Jiroft) and Tapeh Naderi (TN) (Mashhad) based on the microvertebrate and especially Tatera indica species. In these sites we attempted to solve the palaeoenvironment condition by analysis of rodent remains which hold the greatest potential to monitoring of ecological parameters (Hoover et al. 1977; Getz 1961; Reig 1970; Merritt 1974). Combining of a rich network of data with using of morphological and morphometric methods; reconstruction of paleoenvironment; documentation and investigation of their relationship with the environment is the main result of this research. Material & Methods; In both zooarchaeological samples which are composed of juveniles and young individual rodent, (KS, NISP=800 and TN, NISP=3) cranial and postcranial remains were sorted anatomically and washed with water. Dental pattern of mandible and maxillary tooth rows were drowns using a drawing tube connecting to a stereomicroscope (Olympus SZH-10). All recovered teeth fragments were measured based on the greatest dental length and width of the upper and lower jaw molars when possible, with the aid of measuring microscope having accuracy 0.001 mm. One of the main goals of the detailed analysis on dental remains is obtaining the changes of teeth size during time and space (Mashkour and Hashemi 2008). KS remains were recovered out by water sieving a column of three geological sieves with decreasing size of the mesh from top to bottom: 1 cm, 0.5 cm and 0.2 cm. Furthermore, all obtained information, which depending on the type of the skeletal remains has been entered in tables of excel for statistical analysis. Combination of morphometric with morphological studies and their identification keys were used to identify of the remains. Based on these methods, known examples in both archeological sites were belonging to Gerbillinae and Tatera indica species. Discussion of Results & The effect of climate change on Tatera indica species was found for the first time in 1973 in the western regions of Iran and Dehloran plain (10,000-3800 years ago) (Redding 1978). This region has 200 to 399 mm of rainfall per year; rivers, streams, marshes and channels which represents wet conditions in most of the year. In this area, in addition of Tatera indica species, Nesokia indica, Mus musculus, Gerbillus nanus and Meriones crassus were identified. The remains of Tatera indica species with Nesokia and Mus were found also in Shahre shoukhteh in Sistan which wa s reported approximately 6000 years ago (Chaline and Helmer 1974). Presence of Tatera indica in KS site and also in other central, western, southwestern and eastern Iran during the mid to late Holocene can be show that climatic and environmental conditions in the southern half part of the country has not changed from 9000 years to recent (Alley et al. 1997). Finding the dental and cranial remains of Tatera indica in TN of Mashhad and in another archeological site such as Kohandejh in north east of Iran (Nishapur) can be indicate the change climate probably was intense in 2,000 years ago in this part of Iran, because recently, this species not found in northeast of Iran and the maximum their current geographical spread of this species is Torbat-e Jam, while density of these remains were very much in KS, 6000 years ago, (Jiroft).This species is very sensible to cold climate and except of this; it is adaptability with other ecological conditions (Misonne 1959). Addition to Jiroft, obtaining evidence from this remain fauna in other regions of half southern part of Iran showed that from about 10,000 years ago and ever since the Holocene started, with gradual warming of the weather, distribution of this species has not been changed in southern part of Iran, which would be indicative the stability of this species against to warm condition.