Direct ESR dating of the Pleistocene vertebrate assemblage from Khok Sung locality, Nakhon Ratchasima Province, Northeast Thailand

Abstract

We report here the first direct dating study of the faunal assemblage from Khok Sung locality, Thailand. This palaeontological site is of great biochronological, palaeoenvironmental and biogeographical significance. Firstly, it has yielded a rich and diversified Pleistocene vertebrate fauna with up to 15 mammalian species from 13 genera, 10 reptile species, as well as fish and bird remains. Interestingly, while most of the mainland Southeast Asian Pleistocene mammal fossils originate from cave deposits, the Khok Sung fossil layer is located within an 8 m thick fluvial terrace. Secondly, it is geographically located in an area of major importance for reconstructing the migration pathway of large mammals between South China and Java.Combined US-ESR dating of five teeth provides two possible ages of 130 ± 29 ka and 217 ± 36 ka for the fossils. The reason for the occurrence of these two age groups lies in the fact that it was not possible to obtain sediments that were directly associated with the measured samples, nor was it possible to carry out in situ gamma dose rate measurements due to the high water level. Sediment samples recovered from museum specimens show significantly variable concentrations of radioelements. Both options are equally plausible, as independent methods did not provide firm evidence favouring one or the other age range. The results illustrate the intrinsic limitations of the ESR dating method when fossil teeth are not collected in situ during the excavation.Regardless whether the age of the Khok Sung fauna corresponds to MIS 7 or early MIS5, it is nevertheless one of the oldest assemblages directly dated in the region. Further efforts are required for more accurate fossil identification and attribution and for additional numerical dating in this region to improve the biochronological framework of the Pleistocene mammalian faunas in Southeast Asia, which presently remains quite imprecise.

The place beyond the trees: renewed excavations of the Middle Stone Age deposits at Olieboomspoort in the Waterberg Mountains of the South African Savanna Biome

“…We prepared the fossil teeth following a standard ESR dating procedure, as in Duval et al (2019). The enamel layer was mechanically separated from the other dental tissues and both inner and outer surfaces were removed with a dentist drill to eliminate the volume that received an external alpha dose.…”

Long-Term Isotope Evidence on the Diet and Habitat Breadth of Pleistocene to Holocene Caprines in Thailand: Implications for the Extirpation and Conservation of Himalayan Gorals

“…Our stable isotope results also indicate that C. sumatraensis has been well-adapted to variable environmental conditions expanding from closed C 3 to open C 4 landscapes since the Middle Pleistocene and has been a generalist with a greater ecological flexibility in diet and habitat than both Pleistocene and extant Naemorhedus (Figures 2, 4). Although some isotopic data from well-dated localities such as Khok Sung (MIS7 or MIS5) (Suraprasit et al, 2018;Duval et al, 2019;this study) and Nam Lot (MIS5) (Bacon et al, 2018b) as well as from the Early Holocene of Ban Rai Rockshelter have documented the preferred habitat restriction of the Sumatran serows in closed forest environments (Figure 2), this might be explained by the sampling bias for which few specimens are available or analyzed or by the ecological adaptation of C. sumatraensis in response to more homogeneous and closed conditions during interglacial stages. In the heterogeneous environments during the Pleistocene, C. sumatraensis preferably occupied in both closed forest and open grassland landscapes but rarely in an intermediate area between these two canopies.…”

The Chronology of Early Human Settlement in Three Gorges Region, China—Contribution of Coupled Electron Spin Resonance and Uranium-Series Dating Method

“…However, none of them could completely replace the in situ measurement with a portable gamma spectrometer or TL dosimeter, and sometimes measuring the gamma dose rate in variable positions surrounding the dated fossil sample and using the averaged values for the age calculation is the most straightforward way. In the case in situ measurement is not possible, the sediment attached on the surface of the fossil may provide the only choice for external dose rate reconstruction, and the distribution of gamma dose rates may be discussed in order to give a reasonable range of the fossil ESR/U-series ages (Duval et al, 2019).…”