Geoarchaeology of Thamlod Rockshelter, Changwat Mae Hong Son, Northern Thailand

Abstract

This research aims to apply the geological methodologies in interpretating archaeological data at the the Tham Lod rockshelter, a prehistoric site in Changwat Mae Hong Son, Northern Thailand. The objectives of this study are to study relationship among stratigraphy, sedimentology and archaeological records, and to examine land- use pattern and natural resources exploitation in the past. The classification of the stratigraphic sequence has been made on basis of physical analysis, chemical analysis, field observations of site stratigraphy, correlation layers and absolute dating (AMS and TL dating technique). It can be grouped into 4 main in 3 series of geological timescale period as 1) Unit A: Late Pleistocene Period I (dated approximately before 32,000 yr. BP). This unit was created by natural depositional processes. The lower layer of this unit is lateritic soil and overlain by fining upward sequence of gravel in area 1. It can be assumed that the old stream was passed this area. 2.) Unit B: Late Pleistocene Period II (dated approximately 32,000 -10,000 yr. BP).This unit was a complex of deposition which mixed of cultural and natural depositional processes. Cultural process layer is thick depositional layer containing homogeneous of sediments. This unit is composed of high density of artifacts (stone tools, animal remains) which are significant and good evidence of human occupation. They are also an important clue to classify this unit from other unit. The evidence of natural process was examined in area 1 and 2. It was characterized by weathered angular gravel to boulder of limestones, and deposited as lens having incline orientation. This unit was clearly product by limestone rock fall during this period, which might be caused by the neotectonic or earthquake in the past. 3.) Unit C: Early Holocene to Middle Holocene (dated approximately 9980 - 2900 yr. BP). The deposition of this unit shows a gab and unconformity caused by flooding in the past which were characterized by increasing of organic matter and clay particle size (montmorillonite). 4.) Unit D: Late Holocene (approximately dates to after 2,900 yr. BP to present). This unit was a top soil layer deposit. The cultural chronology which implied land use pattern and natural resource exploitation, was established on the basis stratigraphic sequence and archaeological analyses from blocks of random sampling of each excavated area. The chronology divided into four occupational periods. The first was the Late Pleistocene period I comprise of numerous stone tools, animal, shells and fish remains. The spatial distribution indicated that the site was used as a temporary camp and lithic workshop. The second period was the Late Pleistocene period II, Similar of occupation in Late Pleistocene period I but found 2 burial have been found in this period. The Third period is assigned as the Early Holocene to Middle Holocene Period. Archaeological evidence include transported potsherds and beads. Therefore, flooding process might be a major factor affecting a re-deposition of archaeological remains which mixed potsherd and beads together. The fourth period was the Late Holocene Period containing archaeological remain such as potsherd, beads, iron tools. They can be relatively dated to late Holocene.