2015 was incorrect; updated stratigraphy needs to be used in the present paper alongside a simple, clear statement of change from the original interpretations. However, the cave chamber in which they formed may have been completely isolated. Here, a maximum age limit of 414 ka (the upper error limit of OSL5) can be assigned to sub-unit 3b if the OSL ages are taken at face value. The sample has been affected by recrystallization resulting in the formation of radiating acicular crystals of calcite that grow from the core outward. CAM = Central Age Model; MAM = Minimum Age Model. Regardez ! The most important one is that sample RS18 is said to overly Unit 3 (hominin-bearing) in the text, but Unit 2 in the Table. As there are no dates for facies 1c, and as facies 1c is lithologically the same as 1a, this is a hypothesis, not an unquestionable fact. Of course, the data presented as part of this study will provide the age constraints that the reviewer is asking for here. Because the enamel layer analyzed by ESR was not cleaned on both sides, an average external alpha dose rate component of 8 ± 2 μGy a−1 was used based on the alpha attenuation values of Grün (1987). Table 2 presents the actual data from JCU (including the ratios the reviewer refers to) Table 3 presents the actual data from UM. These changes mainly affect the section on ‘lithologic and stratigraphic context for dating’, which has been updated. “Entered” is an interpretation neutral term and can mean many different things. - Line 640/641: Again, Table 1 says RS18 overlies Facies 2b (=Unit2? The laminations are locally recrystallized and overgrown by radiating, elongated crystals of calcite growing from the base to the top of the flowstone layer. Why wasn't radiocarbon dating pursued in the same manner, using established research labs rather than a commercial lab? (a) Comparison of sampling grids across the enamel-dentine boundary measured by SCU-UoW (red lines) vs. GU-ANU (blue circles). Unit 3 is divided into 2 informal members. As a result the ESR results have been presented more clearly, ages and age ranges have now been better and more consistently constrained, and objective and transparent criteria (based on reported age ranges) have been applied consistently throughout the text and figures. The optimal age estimate for the H. naledi fossils, therefore, combines the results from both laboratories with average maximum (i.e., scenario 1) age estimates for samples 1788 and 1810 of 229 + 60/–46 ka and 276 + 59/–77 ka (2 σ uncertainty) respectively, and average minimum (i.e., scenario 2) age estimates of 179 + 49/–40 ka and 220 + 50/–60 ka (2 σ uncertainty) respectively. OSL dating is a radiation dosimetric dating technique based on the time-dependent accumulation of radiation damage in minerals (Adamiec and Aitken, 1998; Murray and Wintle, 2000), as a result of exposure to low levels of ionising radiation in the environment. 5) The U-Th ages must be quoted as just ka, using kyr BP is a radiocarbon convention and does not apply to U-Th - there is no industrial carbon adjustment to U-Th ages, so to quote them as kyr BP is misleading and incorrect. Combined US-ESR ages determined by CENIEH-GU for samples 1810 and 1788 under this scenario are 210 ± 50 ka and 163 ± 24 ka (2σ uncertainty), respectively (Table 7). Areas of enamel with higher U concentrations return older ages (Tables 4 and 5). This suggests a different depositional regime and timing for the sediments and the fossils (Dirks et al., 2015, Dirks et al., 2016a). 6) The reviewers also had suggestions for the order of presentation that may help the reader more readily interpret the results. Videos you watch may be added to the TV's watch history and influence TV recommendations. Each coral standard was analysed by solution MC-ICPMS at UoW and used for reference. Should just stick to the ESR data. This is explained in the methodology section and shown in Figure 10. In particular, the effects of possible post-depositional U uptake, which would result in apparent ages that are younger than the true age, can be assessed with textural analyses (e.g., Pickering et al., 2010), and the use of initial 234U/238U ratios (Tables 2 and 3; Kronfeld et al., 1994). The flowstone is grey-white in colour and preserves 3–6 mm scale laminations visible due to subtle colour variations. This is not uncommon within speleothems (Herries and Shaw, 2011) because a single subsample of 2.5 cm depth is measuring the remanence recorded in multiple layers of speleothem as well as multiple layers of detrital contamination. Many of the equant calcite grains contain remnant aragonite needles, reflecting an earlier phase of aragonite growth. A detailed synthesis of this has now been included in the discussion section under the heading “Reliability of the age estimates”. 5959. 1) The dating is correct. Sample 1841 The baboon tooth consists of an enamel crown that is structurally intact, but the enamel is friable and weathered (Figure 7). I realize there is a Berger et al submission alongside this manuscript which deals with the implications of the age proposed here, but there is still scope for a discussion of both the quality of the age data and what it all means in terms of the formation, development and filling of the Dinaledi Chamber, and of course the deposition and reworking of the hominin fossils. This is again an issue at the end of the paragraph where the facies differ in "relative age and position within the cave chamber", which is not a characteristic of facies. Ages were calculated with Isoplot 3.75 (Ludwig, 2012), and uncertainties are reported as 2 σ. Baseline and drift were corrected using analysis of the NIST 612 glass standard, while two coral standards (the MIS7 Faviid and MIS5 Porites corals from the Southern Cook Islands; Woodroffe et al., 1991) were used to correct 234U/238U and 230U/238U ratios and assess the accuracy of measurements. First, in terms of inaccessibility, we have performed surface geophysics, laser scanning of the chamber, and extensive caving surveys, all of which have yielded zero evidence for alternative entry routes into the Dinaledi Chamber. 1) There is no clear narrative. Internal reworking – where the fossils were originally deposited in a thicker Unit 2 and eroded onto a deflational surface in what is now Unit 3 – would not be likely to change the age, at least not from 200 ka to 1 Ma, since as noted in the preceding paragraph the enclosing sediment remains essentially the same. This is distinct from reworking processes in alluvial settings that involve considerable transport in fluids that would indeed cause considerably greater textural maturity as the reviewer implies. Renaud Ripart, prends ses responsabilités et arrive à battre le portier adverse et inscrit son 7ème but de la saison. This has been rewritten and made much more explicit. - Line 493: Should provide radial plots for the samples for evaluation/visualization of the data. Also, the yellow box in figure 14 is not 200-300 ka, but more like 200-340 ka. The 222Rn loss was confirmed by analyzing a sediment sample that was collected next to sample 1841, for which high resolution, Ge-gamma spectrometry showed ~80% Rn loss. Note that the U-Th ages in the teeth reflect U-uptake events (which are an integral part that dictates the models applied for the ESR dating); they do not reflect a true age for the teeth, but provide an estimate for the minimum age. To obtain a luminescence age, a burial dose (Db) is calculated from the aliquot measurements, in which individual values for De are combined to obtain a single value for Db. The surface of the flowstone has a calcified covering of fine clastic dust that is likely to be much younger. This comparison needs to be made here and would help build an argument as the when the deposition of the fossils took place. This flowstone is white to grey in colour and is finely laminated and partly recrystallized, with recrystallization visible as white, fine, radiating needles of aragonite growing upward from the basal contact, along an irregular alteration front into grey-white, laminated calcite near the top of the layer. The fact that all of the sedimentary material in the cave appears to multiple phases of reworking the same material over and over suggests everything is genetically related and easily dealt with as a series of related units. More importantly, a hanging remnant of sub-unit 3b with hominin material is covered by Flowstone 1c with a lower age limit of 236 ka obtained from the core of a stalactite overlying the rim of the flowstone remnant. This is a well-supported phenomenon in Karst sedimentology. For isotopes measured on the Faradays detectors, the shape of the tail and tailing parameters were defined daily using a >25 V of a solution of U005A; with these parameters a correction for the family of U tails was made. See our explanation under (5), why we have chosen for a relatively light introduction to the methods section. Sample 2 from the top 3 cm of Unit 3 was excluded because of anomalously high Th concentrations (this sample also contains many small bone fragments). "The results for RS18 (~242 ka) may provide a/provide a potential minimum age for the H. naledi fossils in this part of the cave." I appreciate the exhaustive analyses of all techniques at their disposal, although I do have a few concerns regarding their interpretations. In other words, after deposition of Unit 3 commenced to form the talus cone near the entrance of the chamber, parts of the cone slumped and eroded down towards deeper parts of the chamber after Flowstones 1b-e were deposited, but before Flowstone Group 2 was deposited. Ils arrivent des montagnes, bruyants et turbulents ! Phases B and C show normal polarity and phase A shows reversed and intermediate polarity directions. In Table 4 only closed system dates are reported, while Table 5 also lists dates based on the continuous diffusion model of Sambridge et al. A full OSL study of the cave system is being planned. 3) Somewhere, the authors should to be more specific of the possible age of H. naledi from this chamber, versus the best fit age of H. naledi specimens dated here. - Line 200: How can Unit 2 sediments be derived both from local erosion/reworking of Unit 1 and as a debris cone below a vertical fracture system? To obtain a lower age limit for sub-unit 3b, erosional remnants of Unit 1 sediments that were at least partially covered by fossil-bearing sub-unit 3b sediments, were sampled for OSL dating on the assumption that sub-units 1a and 1b in these areas are older than sub-unit 3b (Dirks et al., 2015). The top cartoon should be more of a debris cone without a thick and even deposit running along the floor of the cave. We think it is better not to introduce Facies 3A and 3B for the reasons mentioned by the reviewer: there is a possibility in future that naledi material could be discovered in the Unit 3 sediment, which now appear devoid of fossils. After rinsing, drying and sieving, the fine sand (180–212 µm) fraction was etched for 40 min in 40% hydrofluoric acid to remove the outer layer (~10–15 µm-wide) affected by alpha radiation and any remaining feldspars. This flowstone overlies erosional remnants of well-indurated mud clast breccia assigned to Unit 2 (Figure 3l), and mostly consists of coarsely recrystallized white carbonate.