The potential of teak log coffins collected from Namjang Cave in Northwestern Thailand for studying the coffin culture and paleoclimate in Southeast Asia

Abstract

Ancient teak log coffins found in Namjang (NJ) Cave, Pang Ma Pha district of Mae Hong Son province in Northwestern (NW) Thailand, were dated using a combination of C-14 dating and cross-dating techniques. The longest tree-ring width chronology (i.e., the CoffinNJ index) in Thailand covered a 477-year period from 106 BC to AD 371. The ages of the NJ log coffins fell within the log coffin culture epoch in NW Thailand. The NJ coffins are considered to belong to the second component of the log coffin culture period in NW Thailand, which began from approximately 2100 BP to 1200 BP. Spectral analysis of the CoffinNJ index displayed a decadal periodicity of 11.2 years, similar to the well-known 11-year periodic change in the sunspot cycle. A positive relationship (r = 0.31, p < 0.035) was observed between the CoffinNJ index and sunspot number for the entire period from 110 BC to AD 370, particularly during the period of AD 191–370 (r = 0.48, p < 0.045). Comparisons with speleothem proxies sensitive to changes in solar activity showed relationships between the CoffinNJ index and speleothem parameters (layer thickness: r = − 0.50, p < 0.001 and δ18O: r = 0.40, p < 0.001). The results confirmed that the ancient teak trees in this study might have responded, at least partly, to solar variation. The ring widths of the teak log coffins proved to be a promising proxy for studying the evolution of coffin culture and past climate change in this area.