2018-08-31 - Tim Pietsch - How old was Kiacatoo Man?
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A talk on OSL and U-series dating of the burial site and skeleton of Kiacatoo Man presented to a meeting of the Riverina branch of Soil Science Australia at Mathoura on 31 Aug 2018 by Dr Tim Pietsch, Griffith University (https://experts.griffith.edu.au/9627-tim-pietsch/about).
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2018-08-31 - Tim Pietsch - How old was Kiacatoo Man?
- 1. OSL and U-series dating of the burial site and skeleton of Kiacatoo Man Justine Kemp, Tim Pietsch, Jon Olley, Rainer Grün, Colin Pardoe, Rachel Wood 0
- 2. 1
- 3. Environmental setting 2 Anabranching riverine plains of the Lachlan upstream from Kiacatoo Weir 1. Large meandering Ulgutherie system south of the present river, now Borapine Creek. 2. Reduction in flow producing smaller channel, occasionally underfit. Active flood deposition on levee banks. 3. Channel avulsion to modern Lachlan floodplain 4. Lateral migration within the incised trough with palaeochannels acting as flood channels for the modern river.
- 4. Excavation 33 Excavated skeleton of Kiacatoo Man following removal of the cranium Colin Pardoe examining the emerging fossil OSL sampleOSL samples were extracted from a trench above (3) and below (3) the grave base.
- 5. 4
- 6. 55 Larger right side indicates right- handedness The (healed) finger was likely broken in a fight or accident. Good preservation of bone, but many small fractures from soil movement and [as we now know] vehicle traffic food remains or burial goods?
- 7. Upper arm shaft diameters indicate overall size. Kiacatoo Large body size, “rugosity”, is typical of Pleistocene Australia Kiacatoo Kiacatoo Man Body mass decreases by about 15% in the early Holocene Kiacatoo Man
- 8. 77 Calculated U-series age for each spot (left) and same data plotted against U/Th ratio. Solid line indicates weighted mean averages. U-series results Weighted mean age of 27.4+0.4 ka (minimum age) No evidence for slow diffusion with depth into bone. Therefore assumed fast diffusion-absorption model for U uptake. Excludes U/Th<30 and two outliers.
- 9. OSL results (FMM) Grave infill: 10-17 ka Dose rates 1.7-3.3 Gy/ka 54 6 17 ± 2 10 ± 1 12 ± 1 27 ± 3 18 ± 3 16 ± 2
- 10. Digging your own grave…. Experimental grave digging at Lake Golgolo, Willandra Lakes. Outline of the “grave” is clearly visible.OSL results for “grave fill” and undisturbed substrate Kemp et al. (2014) Journal of Human Evolution
- 11. OSL results (FMM) Underlying substrate: 16-21 ka 1 2 3 18 ± 2 21 ± 2 16 ± 2 35 ± 4 28 ± 3 42 ± 5
- 12. 11 Dr Uta Stockmann (SSSA NSW)
- 13. 1212 OSL results (CAM) 7 8 9 10 Levee and floodplain sediments channel bed sediments 27 ± 2 25 ± 2 40 ± 4 28 ± 2 OD<20% Maximum age of 27 + 2 U-series Minimum age of 27.4 + 0.4 = 27 ka
- 14. 13 Melbourne Sydney Canberra Locations of Pleistocene and Holocene burial grounds and cemeteries in the lower Murray-Darling Basin. After Pardoe (1995)
- 15. Summary • More than one age method is required for significant human fossils. • Kiacatoo Man is largest Pleistocene individual yet discovered in Australia, and possibly the most robust. • Further evidence that “rugosity” or “robusticity” corresponds to the LGM, at least in the eastern tribes. Lithe, gracile desert people inhabited the lower Lachlan, Darling and Murray during the same period. • Kiacatoo Man provides the first direct evidence for a Pleistocene human presence on any of the riverine corridors upstream of Willandra Lakes. • But extensive searches have not been made. Sandy source-bordering dunes and levees may hold the key to understanding the distribution of people during the LGM, whether they ranged widely or retreated to the river systems as the lakes dried. 14
Editor's Notes
- The burial site of Kiacatoo Man was found in a natural levee lying north of this inset channel belt that follows its northern edge for 3 km. Locally the levee is elevated ~1.5 m above the plain with ~ 1.6 m of strong brown silty fine sand of fluvial origin overlying 2.4 m of brown fine sandy silt grading downwards into silty fine sands of the former floodplain. Six OSL samples extracted from the grave fill and from the underlying levee sediment are presently being analysed at Griffith University (Fig. 2A). The modern Lachlan trench lies 1 km north of the burial site and was formed by avulsion away from the Ulgutherie channel belt around the time that the modern flow regime was established.
- The excavation was done in over two days in May when the soil was soft. A trench was dug alongside the skeleton, and samples were extracted for OSL analysis three above andthree below the apparent base of the grave. One behind the ribs. m The Mandible was used for U-series analysis and radiocarbon dating. There was no teeth enamel so ESR was not possible. The mandible was also used for ancient DNA analysis in the Griffith University lab (unsuccessfully). Morphology. The remains are clearly from a very large male, with an estimated height of 6 ft 5 inches. The leg as apparently broken post mortem probably to fit it into the grave. The large, heavily-built legs have the shins folded back against the thigh in a manner only possible some time after death and rigor mortis. The skeleton had been subject to deep mineralisation, was slightly encrusted with carbonate.)
- Elders, community groups assisted with the excavation, and the remains were returned to the grave site 9 months later for reburial.
- Only fragments of the cranium remained along with the right mandibular body (Fig. 2D). The post-cranial skeleton was complete, but fragmented with poor preservation of articular surfaces and other elements with thinner cortical bone. Very little cancellous, or spongy, bone as preserved. Preservation is a relevant, but imprecise indicator of antiquity. The bone was evenly mineralised, but with slightly darker colouration on the external surfaces. No chemical examination of the mineralisation was possible. Manganese staining was not evident. A carbonate wash was present over exposed surfaces and appeared to be of an even thickness on upper and lower surfaces of bone in resting position. The carbonate had infiltrated the bone, assisting the destruction of cancellous bone and exacerbating or causing expansion of micro-fractures so that, while complete in situ, the bones reduced to hundreds of fragments following excavation. Limited reconstruction was possible during the time the remains were in the laboratory. Given the greater amount of carbonate on external surfaces compared to broken edges, it may be that vehicular traffic was responsible for a considerable part of the fracturing. The preservation, with such a degree of mineralisation and carbonate encrustation, is typical of remains that are at least several thousand years old
- Although most of the cranium was fragmented, morphological features of limb bones, skull vault and face indicate an individual of great size and strength. Analysis suggests that Kiacatoo Man would have stood around six feet tall when alive, making him the largest Pleistocene individual yet discovered in Australia. The cranial fragment is as thick as any of the Willandra series, excepting the enigmatic WL 50. From in situ estimation, long bone lengths are at the upper end of the range, exceeded by no more than 2% of an Australian sampling that includes those from mid to early Holocene Rufus River as well as Kow Swamp further upstream in the Murray River corridor. This individual has the largest absolute femoral and tibial diameters of any recorded. Measurements taken from the femur, both length and circumference, place him in the top five percent of Aboriginal measurements along with exceptional rugosity. Although not necessarily the tallest of men, he would have been among the most heavily built.
- Three bone samples were analysed for Th/U dating using laser ablation at the ANU. In order to provide a minimum age estimate for the fossil. (modern bones and teeth are virtually U-free while fossils contain elevated U concentrations). Used a custom-built laser sampling system interfaced between an ArF Excimer laser and a MC-ICP-MS Finnigan Neptune - principles and procedures described in Grün et al. (2014). The bone samples were analysed along lines perpendicular to the outer surface. The results are shown in Table 1 and Figures 3 and 4. All isotopic ratios are expressed as activity ratios. All errors are reported at 2σ, including the calculated ages. There is a relationship between U/Th <30 and Age, owing to detrital 232Th giving age overestimates. Two of the largest outliers, spot 2 of 3008A and spot 5 of 3008B are associated with high U/Th of > 600. None of the profiles show a depth-age relationship as expected from slow diffusion. Thus, we can assume a fast diffusion process for which the best age estimation is derived from the mean values of the individual analyses. As can be seen from Table 1, there are only small differences from the mean ages derived from all measurements and those that exclude Th/U< 30 and the two outliers. The best age estimate derives from the weighted mean of the tracks of 27.4±0.4 ka. But the model makes little difference to the overall results at this age range.
- Single grain measurments performed on quartz at Griffith University. The gamma spectrometry was performed on sediment collected in the lab, ground and measured in well detectors in the lab. The sampling design was based on the expectation that grave infill material would post-date the age of the sediments into which the grave has been cut, enabling us to distinguish the timing of the burial from the timing of initial levee deposition. But the samples within the grave fill are highly overdispersed. This is not uncommon in fluvial deposits, which may have a small number of well bleached grains during transport in deep rivers. But it may also be owing to bioturbation (which you could normally identify from a number of zero aged grains in the mix, or to disturbance. And of course archaeological sites are by definition DISTURBED. Which makes it very difficult to decide which age model to use. The results were modelled using a Finite Mixture Model, because there were clearly different populations of grains, and the Dose determined from the highest proportion component. The highest components had the lowest De and therefore the lowest ages. I have showed the results here in ages rather than doses, although the plots give doses. Of course, age is calculated by dividing dose by the dose rate, which in these all samples we analysed was between 1.7 and 3.3 Gy/ka. The secondary dose components are within 2 sigma error in two cases. But not in the case of Sample No. 4, which produced an “age” similar to the U-series results.
- This is not very surprising, given that grave spoil may not bleach sufficiently in a single exposure event.
- Samples on the underlying substrate provided to be as badly overdispersed, if not more. Again, the application of the FMM will show populations, and the largest component in this case had ages of between 16 and 21 years. With secondary components to these distributions with ages between 28 (again similar to the U series age, and 42 ka). But the overdispersion is worrying. The samples are too close to the surface, even allowing for some surface erosion over the last 150 years of sheep grazing and other activities. So in the end we decided that none of these OSL ages was reliable.
- In the Lachlan-Willandra system, source-bordering dunes and levees may hold the key to understanding the distribution of people during the coldest phase of the LGM: whether they were able to range widely or retreated to the river systems as the lakes dried. So far, apart from Kiacatoo Man, there is no direct evidence of a human presence on any of the riverine corridors upstream of Willandra Lakes before 15,000 years (Pardoe, 1995),