Elsevier

Vibrational Spectroscopy

Volume 105, November 2019, 102980
Vibrational Spectroscopy

Investigations of the Neolithic potteries of 6th millennium BC from Göytepe-Azerbaijan by vibrational spectroscopy and chemometric techniques

https://doi.org/10.1016/j.vibspec.2019.102980Get rights and content

Abstract

This article presents the results of the vibrational spectroscopic and chemometric analyses of Neolithic pottery remains excavated in Göytepe (Azerbaijan), a typical Shomutepe-Shulaveri culture settlement. Fifty-five pottery fragments, that were unearthed in the excavations of Göytepe during the 2009–2013 years, were investigated using Fourier Transform Infrared (FTIR) and micro-Raman spectroscopy. X-Ray Diffraction (XRD) was used as a complementary technique. The firing-temperature and -conditions were inferred from the mineral phases obtained from the vibrational spectra of the samples and were estimated to be between 600 °C and 750 °C in oxidizing atmosphere. As chemometrics, Principal Component Analysis (PCA) followed by Linear Discriminant Analysis (LDA), were applied to the FTIR spectral data, in order to examine the possible classification of those findings, and to extract the most discriminant features. Pottery fragments were identified and characterized, depending on the excavation levels, by PCA-LDA analysis.

Introduction

The Southern Caucasus, with its rich and versatile fauna and flora and an abundance of mineral sources, including metal ores, provided a favorable basis for the establishment of early human cultures. Azerbaijan has a rich archaeological past. The Tovuz region of Azerbaijan has an ancient settlement of Neolithic period. Tovuz is located in the western part of Azerbaijan on the border with Georgia, 426 km from Baku. One of the largest Neolithic settlements in Azerbaijan is the site of Göytepe, located in the Tovuz region, in a marginal area between two main alluvial fans formed by the Zayam River to the east and the Asrik River to the west [1]. The radiocarbon analysis of the found samples of the material culture of the Neolithic period showed that the oldest settlement in the region was in this area and dated back to sixth millennium BC [2]. Göytepe represents one of the oldest agricultural villages thus far known in the region [1].

Potteries are the most abundant inorganic evidences of ancient life. They have importance as a carrier of information about ancient cultures, and are source of materials on many aspects of the past such as civilization, trade and technology [[3], [4], [5]].

Potteries are made of clay minerals with some inclusions. Clay minerals show some characteristic reactions during the firing; e.g. dehydroxylation, decomposition and phase transformation [6]. Thus by investigation of the mineral composition of the pottery, knowledge about the firing temperature and firing technology can be obtained. Our paper focuses on the vibrational spectroscopic study of 55 potsherds that were unearthed in the excavations of Göytepe during the 2009–2013 years. In order to reveal data embedded IR spectra, multivariate statistical methods were used which provide the ability to analyze the vast spectral distribution. The combination of the Principal Component Analysis (PCA) with the Linear Discriminant Analysis (LDA), is a powerful tool for the analysis of the FTIR spectra of the archaeological artefacts.

The present work aims to characterize the Neolithic potteries from Göytepe-Azerbaijan, and to distinguish the samples obtained from different occupational levels. This research represents the first systematic archaeometric study of the terra cotta fragments from Göytepe. For these purposes, the mineralogical composition and firing temperatures of the pottery fragments of Göytepe were investigated by FTIR and micro-Raman spectroscopy. Multivariate statistical methods were used for the recognition of local pottery production and distinguishing the potteries unearthed in different archaeological levels.

Section snippets

Excavation site Göytepe

Göytepe (40˚58′11.84˝ N; 45˚42′17.81˝ E, ca. 430 m a.s.l.), in the Tovuz region of Azerbaijan, is an ancient Neolithic settlement of the South Caucasus (western Azerbaijan) (see Fig. 1A). The ancient settlement is located at the south part of the Kura River, on a large alluvial plain at the northern foot of the Lesser Caucasus Mountains. The excavations at Göytepe have been going on since 2008. However, the investigated potteries were collected in the 2009–2013 excavations. Archaeological

Description of samples

In this study, totally 55 pottery fragments obtained from six archaeological building levels (0th to 5th layer in depth) of Göytepe archaeological site were analyzed;{12 from 0th level; 9 from 1st level; 7 from 2nd level; 5 from 3th level; 14 from 4th level; 8 from 5th level). The excavation in Göytepe was firstly conducted using a 10 × 10 m grid system, designated by numbers (1, 2, 3…) from the datum point at the summit of the mound to the north, and by the alphabet (A, B, C…) to the east [2].

FTIR and Raman spectroscopic study

The FTIR spectra of the representative samples are shown in Fig. 4. Over all similarity of all spectra is in silica bands. An intense asymmetric stretching vibrational mode of SiO(Si) [νa(Sisingle bondO)] at about 1000 cm−1 and medium intense Si/Al-O-Si bending vibration, at about 460 cm−1 are observed. In addition, there are bands due to the presence of water and hydroxyl groups. The IR spectra show that all samples contain different amounts of calcite (ca. 1430 cm−1) and quartz (795, 776 and 693 cm−1).

Conclusions

In this study 55 pottery fragments, obtained from uppermost part (0th level) into the 5th building levels of the excavation site Göytepe (Azerbaijan) were investigated by FTIR, micro-Raman, and chemometric techniques. The FTIR and Raman data provide a detailed description of the minerals of which the findings consist of. The clay types of the samples are found to be mainly illite and kaolinite. The whole set of samples shows a general similarity in the mineralogical composition. Calcite

Declaration of Competing Interest

There is no conflict interest with this manuscript.

Acknowledgement

This study is supported by Istanbul Kultur University (project No U2407/52/05).

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