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Geological and taphonomic context for the new hominin species Homo naledi from the Dinaledi Chamber, South Africa.

Dirks PH, Berger LR, Roberts EM, Kramers JD, Hawks J, Randolph-Quinney PS, Elliott M, Musiba CM, Churchill SE, de Ruiter DJ, Schmid P, Backwell LR, Belyanin GA, Boshoff P, Hunter KL, Feuerriegel EM, Gurtov A, Harrison Jdu G, Hunter R, Kruger A, Morris H, Makhubela TV, Peixotto B, Tucker S - Elife (2015)

Bottom Line: The chamber was always in the dark zone, and not accessible to non-hominins.Bone taphonomy indicates that hominin individuals reached the chamber complete, with disarticulation occurring during/after deposition.Preliminary evidence is consistent with deliberate body disposal in a single location, by a hominin species other than Homo sapiens, at an as-yet unknown date.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth and Oceans, James Cook University, Townsville, Australia.

ABSTRACT
We describe the physical context of the Dinaledi Chamber within the Rising Star cave, South Africa, which contains the fossils of Homo naledi. Approximately 1550 specimens of hominin remains have been recovered from at least 15 individuals, representing a small portion of the total fossil content. Macro-vertebrate fossils are exclusively H. naledi, and occur within clay-rich sediments derived from in situ weathering, and exogenous clay and silt, which entered the chamber through fractures that prevented passage of coarser-grained material. The chamber was always in the dark zone, and not accessible to non-hominins. Bone taphonomy indicates that hominin individuals reached the chamber complete, with disarticulation occurring during/after deposition. Hominins accumulated over time as older laminated mudstone units and sediment along the cave floor were eroded. Preliminary evidence is consistent with deliberate body disposal in a single location, by a hominin species other than Homo sapiens, at an as-yet unknown date.

No MeSH data available.


Related in: MedlinePlus

Comparison of selected fragments and electron microprobe analytical data of Facies 2 (Unit 3, floor) sediment in the Dinaledi Chamber, and floor sediments in the Dragon's Back Chamber.Analytical spot size is 5 μm diameter, which is generally larger than grain sizes. (A) Chert fragment impregnated with Mn oxi-hydroxide from the Dragon's Back Chamber. (B) Shale fragment from the Dragon's Back Chamber. (C) orange mud clast, typical of Facies 2 sediments from the Dinaledi Chamber, note much finer grain size than seen in (B). (D–G) Plots of K2O vs Al2O3 for mud clast fragments in Facies 2 samples from both chambers show an important difference between them. M, muscovite compositional field. The samples from the Dinaledi Chamber (E–G) yield some data close to the muscovite field, probably indicating sericite grains slightly smaller than the spot size, and all show a trend with K/Al ratios much lower than muscovite, up to a high Al2O3 content >30%, which indicates either illite, or mixtures of sericite and kaolinite or other K-free clay minerals. In (E) the analysis of the fragment shown in (C) is indicated. The sample from the Dragon's Back Chamber in (D) shows data in the muscovite field (data point corresponding to [B] is indicated in [D]), but otherwise only low K- and Al-concentrations, which are typical of Mn oxi-hydroxide impregnation (data point corresponding to [a] is indicated in [D]). No analytical data in d correspond to mudstone fragments such as shown in (C). (H–K), plots of Fe as FeO vs Mn as MnO show similarity between the chambers with respect to Fe-Mn oxi-hydroxide impregnations and alterations within the fragments: in both cases, domains with high Fe rarely coincide with domains high in Mn. (L–O), Plots of F vs Mn as MnO. Some elevated F concentrations at zero Mn values occur, but most data show a correlation for samples from both chambers: elevated Mn content is invariably associated with elevated F, with an atomic ratio F/Mn ≈ 0.14. No Mn oxi-hydroxide minerals with F have been described, but partial substitution of F− for OH− as in apatite might be suspected. The similarity of the F/Mn ratios in Mn oxi-hydroxide impregnated fragments from Facies 2 sediments in both chambers suggests a uniform geochemical environment during the Mn oxi-hydroxide alteration event.DOI:http://dx.doi.org/10.7554/eLife.09561.010
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fig8: Comparison of selected fragments and electron microprobe analytical data of Facies 2 (Unit 3, floor) sediment in the Dinaledi Chamber, and floor sediments in the Dragon's Back Chamber.Analytical spot size is 5 μm diameter, which is generally larger than grain sizes. (A) Chert fragment impregnated with Mn oxi-hydroxide from the Dragon's Back Chamber. (B) Shale fragment from the Dragon's Back Chamber. (C) orange mud clast, typical of Facies 2 sediments from the Dinaledi Chamber, note much finer grain size than seen in (B). (D–G) Plots of K2O vs Al2O3 for mud clast fragments in Facies 2 samples from both chambers show an important difference between them. M, muscovite compositional field. The samples from the Dinaledi Chamber (E–G) yield some data close to the muscovite field, probably indicating sericite grains slightly smaller than the spot size, and all show a trend with K/Al ratios much lower than muscovite, up to a high Al2O3 content >30%, which indicates either illite, or mixtures of sericite and kaolinite or other K-free clay minerals. In (E) the analysis of the fragment shown in (C) is indicated. The sample from the Dragon's Back Chamber in (D) shows data in the muscovite field (data point corresponding to [B] is indicated in [D]), but otherwise only low K- and Al-concentrations, which are typical of Mn oxi-hydroxide impregnation (data point corresponding to [a] is indicated in [D]). No analytical data in d correspond to mudstone fragments such as shown in (C). (H–K), plots of Fe as FeO vs Mn as MnO show similarity between the chambers with respect to Fe-Mn oxi-hydroxide impregnations and alterations within the fragments: in both cases, domains with high Fe rarely coincide with domains high in Mn. (L–O), Plots of F vs Mn as MnO. Some elevated F concentrations at zero Mn values occur, but most data show a correlation for samples from both chambers: elevated Mn content is invariably associated with elevated F, with an atomic ratio F/Mn ≈ 0.14. No Mn oxi-hydroxide minerals with F have been described, but partial substitution of F− for OH− as in apatite might be suspected. The similarity of the F/Mn ratios in Mn oxi-hydroxide impregnated fragments from Facies 2 sediments in both chambers suggests a uniform geochemical environment during the Mn oxi-hydroxide alteration event.DOI:http://dx.doi.org/10.7554/eLife.09561.010

Mentions: The three samples of Unit 3 from the Dinaledi Chamber (SO31, 34, 39; Figures 2C and 5D,E, 8) are dominated by reworked, angular mud clasts in a clay matrix, with some chert fragments, but with little externally derived detrital quartz. The sample from the Dragon's Back Chamber is dominated by detrital quartz, with some detrital muscovite, as well as shale and chert fragments, of which some are altered and impregnated and/or coated with Mn- and Fe-oxides. Mudstone fragments are rare in DB-1 (Figures 5C and 8). Elevated MnO (3.9–4.2%) and Fe2O3 (10.3–11%) levels in the floor sediments of both chambers are associated with alteration of chert or mudstone prior to their comminution, with Mn- and Fe oxides/hydroxides occurring as replacement and micro-vein infilling. XRD diffractograms identified both quartz and muscovite in all samples with high scores compared to other minerals. Hematite was identified with high scores in all the Dinaledi samples. Goethite (FeO(OH)) and birnessite ((Na,Ca,K)(Mn4+,Mn3+)2O4·1.5H2O) were only identified in UW101-SO-31, with low scores, but high certainty. Other minerals identified with low scores and high certainties are dolomite ((CaMg)(CO3)2) in UW101-SO-34 and kaolinite (Al2Si2O5(OH)4) in UW101-SO-39. Using XRD, only quartz and muscovite were identified in DB-1. Acid tests showed all samples to be free of calcite or aragonite. All analysed Mn oxi-hydroxides in both chambers contain fluorine, with similar (atomic) F/Mn ratios of ≈ 0.14, indicating a similar chemical environment during their formation. Different patterns in K2O vs Al2O3 plots reflect a dominance of mudstone fragments consisting mainly of clay minerals, in the Dinaledi Chamber, and the presence of muscovite in the Dragon's Back Chamber (Figure 8). The contrasting composition in particulate matter of floor sediments in the two chambers, suggests that the Dinaledi Chamber was an isolated sedimentary environment at the time of deposition of Unit 3, with no or very limited transfer of sediment between the two chambers.10.7554/eLife.09561.010Figure 8.Comparison of selected fragments and electron microprobe analytical data of Facies 2 (Unit 3, floor) sediment in the Dinaledi Chamber, and floor sediments in the Dragon's Back Chamber.


Geological and taphonomic context for the new hominin species Homo naledi from the Dinaledi Chamber, South Africa.

Dirks PH, Berger LR, Roberts EM, Kramers JD, Hawks J, Randolph-Quinney PS, Elliott M, Musiba CM, Churchill SE, de Ruiter DJ, Schmid P, Backwell LR, Belyanin GA, Boshoff P, Hunter KL, Feuerriegel EM, Gurtov A, Harrison Jdu G, Hunter R, Kruger A, Morris H, Makhubela TV, Peixotto B, Tucker S - Elife (2015)

Comparison of selected fragments and electron microprobe analytical data of Facies 2 (Unit 3, floor) sediment in the Dinaledi Chamber, and floor sediments in the Dragon's Back Chamber.Analytical spot size is 5 μm diameter, which is generally larger than grain sizes. (A) Chert fragment impregnated with Mn oxi-hydroxide from the Dragon's Back Chamber. (B) Shale fragment from the Dragon's Back Chamber. (C) orange mud clast, typical of Facies 2 sediments from the Dinaledi Chamber, note much finer grain size than seen in (B). (D–G) Plots of K2O vs Al2O3 for mud clast fragments in Facies 2 samples from both chambers show an important difference between them. M, muscovite compositional field. The samples from the Dinaledi Chamber (E–G) yield some data close to the muscovite field, probably indicating sericite grains slightly smaller than the spot size, and all show a trend with K/Al ratios much lower than muscovite, up to a high Al2O3 content >30%, which indicates either illite, or mixtures of sericite and kaolinite or other K-free clay minerals. In (E) the analysis of the fragment shown in (C) is indicated. The sample from the Dragon's Back Chamber in (D) shows data in the muscovite field (data point corresponding to [B] is indicated in [D]), but otherwise only low K- and Al-concentrations, which are typical of Mn oxi-hydroxide impregnation (data point corresponding to [a] is indicated in [D]). No analytical data in d correspond to mudstone fragments such as shown in (C). (H–K), plots of Fe as FeO vs Mn as MnO show similarity between the chambers with respect to Fe-Mn oxi-hydroxide impregnations and alterations within the fragments: in both cases, domains with high Fe rarely coincide with domains high in Mn. (L–O), Plots of F vs Mn as MnO. Some elevated F concentrations at zero Mn values occur, but most data show a correlation for samples from both chambers: elevated Mn content is invariably associated with elevated F, with an atomic ratio F/Mn ≈ 0.14. No Mn oxi-hydroxide minerals with F have been described, but partial substitution of F− for OH− as in apatite might be suspected. The similarity of the F/Mn ratios in Mn oxi-hydroxide impregnated fragments from Facies 2 sediments in both chambers suggests a uniform geochemical environment during the Mn oxi-hydroxide alteration event.DOI:http://dx.doi.org/10.7554/eLife.09561.010
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fig8: Comparison of selected fragments and electron microprobe analytical data of Facies 2 (Unit 3, floor) sediment in the Dinaledi Chamber, and floor sediments in the Dragon's Back Chamber.Analytical spot size is 5 μm diameter, which is generally larger than grain sizes. (A) Chert fragment impregnated with Mn oxi-hydroxide from the Dragon's Back Chamber. (B) Shale fragment from the Dragon's Back Chamber. (C) orange mud clast, typical of Facies 2 sediments from the Dinaledi Chamber, note much finer grain size than seen in (B). (D–G) Plots of K2O vs Al2O3 for mud clast fragments in Facies 2 samples from both chambers show an important difference between them. M, muscovite compositional field. The samples from the Dinaledi Chamber (E–G) yield some data close to the muscovite field, probably indicating sericite grains slightly smaller than the spot size, and all show a trend with K/Al ratios much lower than muscovite, up to a high Al2O3 content >30%, which indicates either illite, or mixtures of sericite and kaolinite or other K-free clay minerals. In (E) the analysis of the fragment shown in (C) is indicated. The sample from the Dragon's Back Chamber in (D) shows data in the muscovite field (data point corresponding to [B] is indicated in [D]), but otherwise only low K- and Al-concentrations, which are typical of Mn oxi-hydroxide impregnation (data point corresponding to [a] is indicated in [D]). No analytical data in d correspond to mudstone fragments such as shown in (C). (H–K), plots of Fe as FeO vs Mn as MnO show similarity between the chambers with respect to Fe-Mn oxi-hydroxide impregnations and alterations within the fragments: in both cases, domains with high Fe rarely coincide with domains high in Mn. (L–O), Plots of F vs Mn as MnO. Some elevated F concentrations at zero Mn values occur, but most data show a correlation for samples from both chambers: elevated Mn content is invariably associated with elevated F, with an atomic ratio F/Mn ≈ 0.14. No Mn oxi-hydroxide minerals with F have been described, but partial substitution of F− for OH− as in apatite might be suspected. The similarity of the F/Mn ratios in Mn oxi-hydroxide impregnated fragments from Facies 2 sediments in both chambers suggests a uniform geochemical environment during the Mn oxi-hydroxide alteration event.DOI:http://dx.doi.org/10.7554/eLife.09561.010
Mentions: The three samples of Unit 3 from the Dinaledi Chamber (SO31, 34, 39; Figures 2C and 5D,E, 8) are dominated by reworked, angular mud clasts in a clay matrix, with some chert fragments, but with little externally derived detrital quartz. The sample from the Dragon's Back Chamber is dominated by detrital quartz, with some detrital muscovite, as well as shale and chert fragments, of which some are altered and impregnated and/or coated with Mn- and Fe-oxides. Mudstone fragments are rare in DB-1 (Figures 5C and 8). Elevated MnO (3.9–4.2%) and Fe2O3 (10.3–11%) levels in the floor sediments of both chambers are associated with alteration of chert or mudstone prior to their comminution, with Mn- and Fe oxides/hydroxides occurring as replacement and micro-vein infilling. XRD diffractograms identified both quartz and muscovite in all samples with high scores compared to other minerals. Hematite was identified with high scores in all the Dinaledi samples. Goethite (FeO(OH)) and birnessite ((Na,Ca,K)(Mn4+,Mn3+)2O4·1.5H2O) were only identified in UW101-SO-31, with low scores, but high certainty. Other minerals identified with low scores and high certainties are dolomite ((CaMg)(CO3)2) in UW101-SO-34 and kaolinite (Al2Si2O5(OH)4) in UW101-SO-39. Using XRD, only quartz and muscovite were identified in DB-1. Acid tests showed all samples to be free of calcite or aragonite. All analysed Mn oxi-hydroxides in both chambers contain fluorine, with similar (atomic) F/Mn ratios of ≈ 0.14, indicating a similar chemical environment during their formation. Different patterns in K2O vs Al2O3 plots reflect a dominance of mudstone fragments consisting mainly of clay minerals, in the Dinaledi Chamber, and the presence of muscovite in the Dragon's Back Chamber (Figure 8). The contrasting composition in particulate matter of floor sediments in the two chambers, suggests that the Dinaledi Chamber was an isolated sedimentary environment at the time of deposition of Unit 3, with no or very limited transfer of sediment between the two chambers.10.7554/eLife.09561.010Figure 8.Comparison of selected fragments and electron microprobe analytical data of Facies 2 (Unit 3, floor) sediment in the Dinaledi Chamber, and floor sediments in the Dragon's Back Chamber.

Bottom Line: The chamber was always in the dark zone, and not accessible to non-hominins.Bone taphonomy indicates that hominin individuals reached the chamber complete, with disarticulation occurring during/after deposition.Preliminary evidence is consistent with deliberate body disposal in a single location, by a hominin species other than Homo sapiens, at an as-yet unknown date.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth and Oceans, James Cook University, Townsville, Australia.

ABSTRACT
We describe the physical context of the Dinaledi Chamber within the Rising Star cave, South Africa, which contains the fossils of Homo naledi. Approximately 1550 specimens of hominin remains have been recovered from at least 15 individuals, representing a small portion of the total fossil content. Macro-vertebrate fossils are exclusively H. naledi, and occur within clay-rich sediments derived from in situ weathering, and exogenous clay and silt, which entered the chamber through fractures that prevented passage of coarser-grained material. The chamber was always in the dark zone, and not accessible to non-hominins. Bone taphonomy indicates that hominin individuals reached the chamber complete, with disarticulation occurring during/after deposition. Hominins accumulated over time as older laminated mudstone units and sediment along the cave floor were eroded. Preliminary evidence is consistent with deliberate body disposal in a single location, by a hominin species other than Homo sapiens, at an as-yet unknown date.

No MeSH data available.


Related in: MedlinePlus