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We employ high-throughput thermal-neutron tomographic imaging to visualise internal diagnostic features of dense fossiliferous breccia from three Pleistocene cave localities in Sumatra, Indonesia. We demonstrate that these seemingly homogeneous breccias are an excellent source of data to aid in determining taphonomic and depositional histories of complex depositional sites such as tropical caves. X-ray Computed Tomographic (CT) imaging is gaining importance amongst palaeontologists as a non-destructive approach to studying fossil remains. Traditional methods of fossil preparation risk damage to the specimen and may destroy contextual evidence in the surrounding matrix. CT imaging can reveal the internal composition and structure of fossils contained within consolidated sediment/rock matrices prior to any destructive mechanical or chemical preparation. Neutron computed tomography (NCT) provides an alternative contrast to X-rays, and in some circumstances, is capable of discerning denser matrices impenetrable to or yielding no contrast with CT imaging. High-throughput neutron imaging reduces neutron fluence during scanning which means there is less residual neutron-induced radioactivation in geological samples; allowing for earlier subsequent analyses. However, this approach remains unutilised in palaeontology, archaeology or geological surveys. Results suggest that the primary agents in the formation of the breccias and concentration of incorporated vertebrate remains are several rapid depositional phases of water and sediment gravity flow. This study highlights the potential for future analyses of breccia deposits in palaeontological studies in caves around the world.

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We provide the first numerical age constraints for the palaeontological assemblage and associated sediment from Ngalau Sampit, Sumatra, one of M. Eugène F.T. Dubois' noted sites that he excavated in 1889, and of which we present a transcript of his unpublished report. A combination of U-series, Electron Spin Resonance (ESR) and Luminescence (pIR-IRSL) methods was employed. The three tooth samples yield 1σ consistent combined U-series/ESR ages (mean age of 105 ± 9 ka, 1 s.d.), supporting the chronological integrity of the fossil assemblage at Ngalau Sampit. Three breccia samples yield internally 1σ consistent pIR-IRSL age estimates (mean age of 93 ± 6 ka, 1 s.d.), suggesting that the breccia may represent one single depositional event. All these results are compatible with the U-series age estimates previously obtained on post-depositional carbonate formations. We cannot exclude that the existing, and systematic, age difference between ESR and pIR-IRSL methods (~12 ka on average) may reflect the difference in the dated events (death of the animals vs. sediment burial). However, this apparent deviation is most likely not significant (mean ages are in close agreement a 1σ) and results from the existing uncertainty around the evaluation of the gamma dose rate, which partly arises from the absence of in situ dosimetry. Despite this uncertainty, all the numerical ages consistently and systematically correlate the breccia and associated fossil assemblage to MIS 5 (a finer correlation to sub-stages within MIS 5 would most likely be too speculative at this stage). Ngalau Sampit represents only the third site from the Pandang Highlands to be radiometrically dated, after Lida Ajer and Ngalau Gupin, and the second site explored and recorded by Dubois to have associated dates. Finally, Ngalau Sampit is the only site in Sumatra that chronologically correlates to MIS 5, and thus with the regionally important site of Punung in Java.

The northern lobe of the White River Ash (WRAn) is part of a bilobate distribution of tephras that originated from the Wrangell Volcanic Field near the border of Alaska, USA, and Yukon, Canada. It is distributed across northeastern Alaska and the northwestern portion of the Yukon. The timing of this eruption has seen little critical analysis relative to the younger and more extensive eastern lobe eruption of the White River Ash. We compiled 38 radiocarbon (14C) dates from above and below the WRAn, and employed several statistical approaches to identify and eliminate or down-weight outliers, combine dates, and different Bayesian models, to provide a revised age estimate for the timing of the WRAn tephra deposition. Our results indicate that the most accurate modeled age estimate for the northern lobe of the White River Ash deposition is between 1689 and 1560 cal BP, with a mean and median of 1625 and 1623 cal BP, respectively. This age range is 90 to 200 years younger than previous age estimates.