Photo: Ulrich Bismayer

Left: Pre-metal Age sherd (AMS, radiocarbon age 3609 ± 29 BP) (BP=1950), Middle: Bronze Age (3000 – 2300 BP), Right: Iron Age (2300 – 1800 BP).

Recognisable geometric patterns appear on well preserved ancient ceramics from the archaeological UNESCO world heritage site Ban Chiang, Thailand.

Depending on their age, surfaces of those ceramics show cord-marks, roller traces, impressions and incisions (Pre-metal Age) or red hematite pigment painted patterns (Iron Age). Mineralogical and chemical analysis of ceramic artefacts from different newly discovered excavation sites will help to better understand used materials and possible connections between the sites and their population. Parent rocks of the present Northeast Thailand were Cretaceous granites, granodiorites and pegmatites which became after weathering raw materials for the local ceramic makers. Our previous studied Ban Chiang ceramics of Iron Age show recognizable patterns with mainly hematite in their red pigment while quartz and clay minerals dominate the bulk composition.

Pre-metal Age ceramics from Ban Chiang (determined age ca. 3700 years) have a black surface because of reducing conditions during firing around 1200 K, which is compatible with the formation of the mineral mullite in the bulk. Synchrotron tomographic studies show that the older Pre-metal Age samples have larger pore volumes than Bronze and Iron-Age ceramics. Pre-metal Age samples contain phyllosilicate minerals with less OH- compared to younger shards as shown by FTIR studies.

On the elevated Khorat Plateau (ca. 90-250 m above sea-level) in Northeast Thailand further archaeological excavation sites have been discovered, namely Non Nok Tha and Don Up Mung which raises the question of the connection between craftmanship respectively their delineation separating different sites. Up to now, apart from age determination, no detailed mineralogical study was done on artefacts from Non Nok Tha and Don Up Mung nor compared with Ban Chiang ceramics. So far it remains unclear if such surface patterns are unique for the Ban Chiang site nor what meaning they conveyed. Hence, detailed analysis of the pigment chemistry, mineral composition of the ceramics and firing techniques at different excavation sites can provide insights into Iron Age pottery, earlier bronze production techniques, possible links between the aforementioned locations and transitions in prehistoric human activity within the elevated Indochina micro-plate.

Samples from museums in Ban Chiang and Khon Kaen from different sites were selected for comparison of surface patterns, their mineralogical surface and bulk compositions. The excavation sites are roughly 150 km distant from each other in the same geological Korat Plateau corridor and they are connected via river paths, hence, social interactions were likely.

Ongoing collaboration with colleagues from the Synchrotron Light Research Institute, Nakhon Ratchasima (SLRI) Thailand, on archaeological samples from the different sites was approved by the Department of Fine Arts (DFA) Bangkok.

People

Project Lead:

• Ulrich Bismayer

Collaborators:

• Synchrotron SLRI
• Nakhon Ratchasima Thailand:
  • Somchai Tancharakorn
  • Waraporn Tanthanuch
  • Wutthikrai Busayaporn
• Sutham Srilomsak (Khon Kaen University)
• Kanokwalee Suriyatham (Fine Arts Department Ban Chiang National Museum)

Duration

• 2026–2029