การกำหนดอายุด้วยเทคนิคอิเล็กตรอนสปินเรโซแนนซ์ของซากหอยน้ำจืดจากแหล่งโบราณคดีเพิงผาปาโต๊ะโระ ถ้ำเขาหาน จังหวัดสตูล ภาคใต้ของประเทศไทย

Abstract

The Office of the Fine Arts Department 13th Songkhla has surveyed and excavated archaeological sites, in the lower south of Thailand which found evidence of both antiquities and many ecological objects such as human skeletons, pottery, fossil shells, and animal bones, one of the archaeological sites is Pa Toh Roh Shelter Archaeological site, Khao Han Cave, Satun Province, Southern Thailand. In this study, the electron spin resonance (ESR) technique was utilized to determine the age of six freshwater fossil shells collected from the Pa Toh Roh Shelter Archaeological site at three distinct depths. Freshwater fossil shells clams with the codes SH1-010, SH2-123, SH3-248 (level 2, 70–80 cm), SH3-028, SH5-253 (level 3, 80–90 cm), and SH6-140 (level 4, 90–100 cm). X-ray diffraction (XRD) examination of samples revealed the crystal structures of aragonite and calcite. The characteristics of ESR signals from freshwater shells crystal powder, size 90-150 µm, were studied. The ESR signal before irradiation was found two characteristics, that is, six-line signal and double line signal. The six line signal indicated to be manganese ions (Mn2+) and double line signal, caused by the reaction between limestone of calcium carbonate in freshwater shells and humidity. After irradiation with 120 Gy of dose, it was discovered that the signal generated by manganese ions (Mn2+) did not increase when various radiation doses. However, increasing the area under the magnetic field between 349-352 mT can reveal the type of signal produced. It consists of signals generated by molecular ions SO2 - and SO3 - with values g = 2.0057 and g = 2.0031, respectively, and molecular ions CO2 - with g = 2.0016 and g = 1.9973. Analysis of these results revealed that the signal at g = 2.0016 caused by the molecular ion CO2 - was also suitable for the accumulated dose analysis utilized in age determination by the ESR technique. By studying the correlation curve of ESR signal intensity increasing from gamma ray irradiation from 0-120 Gy by additive dose method, it was found that there was a linear relationship. and the accumulated dose was 11.32±0.39 Gy to 22.84±0.76 Gy. Later, an analysis was performed to determine the annual dose of radiation. By measuring the concentration of radioactive elements in nature (U-238, Th-232, and K-40) in the freshwater shells samples and the soil surrounding the samples, as well as the cosmic ray exposure, the range was determined to be between 2.88±0.07 and 6.90±0.06 mGy/y. As a result of the accumulated dose and annual doses. Analyzing the ages of freshwater shells showed a range of ages between 3,310±115 and 4,655±210 years. The age of the samples discovered here shows that it dates back to the prehistoric era. Similar to adjacent archaeological sites, it dates to the Neolithic period. In addition, the age determined was consistent with the results of the report on the relative age determination of the Office of the Fine Arts Department 13th Songkhla, which included the examination of freshwater shells remains. Prior research into thermoluminescence techniques.