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Palaeoenvironmental reconstruction of the late pleistocene to early holocene robertson cave sedimentary deposit, Naracoorte, South Australia

Journal Article


Abstract


  • Sedimentological investigations and geochemical analyses of the Robertson Cave deposit, 7 km south of Naracoorte, South Australia, document a palaeoenvironmental record for the Late Pleistocene and Early Holocene. Three distinct depositional episodes spanning the interval 32-8 ka are represented by over 4 m of sediments exposed in the chamber 2 excavation pit. The oldest of the three, the lower unit (>30 ka BP) is dominated by reddish and brown sandy silts. A 20 cm band of red silt horizons that cap this unit contain enriched ��15N values (12-15���), low C/N ratios, significant SO3 (20%) and CaO (18.5%) contents, a high alkyl-C component and phosphorus-rich mineralogy. These unique sediment horizons are interpreted as being derived from the accumulation of bat guano and degraded cave rock fragments. Their presence suggests a period of low sediment input into the cave, possibly reflecting the existence of a stable geomorphic environment prior to 30 ka. The time period 30-27 ka saw the rapid deposition of the middle unit, a sequence of coarser homogeneous sands that resulted in the entrance to chamber 2 becoming blocked. These horizon-less sediments, with clear aeolian features, are most likely representative of the drier conditions associated with the Last Glacial Maximum, which peaked at 20-17 ka. Deposition into the chamber recommenced at approximately 13 ka and continued until 8 ka, resulting in the accumulation of the upper unit, a sequence of silt, charcoal and organic matter rich horizons. Here, a shift to more 13C-depleted values (-25���to -27���) is evident in the bulk soil organic matter and charcoal between 11 and 10 ka, possibly reflecting a shift from the dry Last Glacial Maximum to the wetter environs of the Holocene. The upper unit may also be a record of burning practices associated with Aboriginal migration to the area.

UOW Authors


  •   Forbes, Matthew (external author)

Publication Date


  • 2007

Citation


  • Forbes, M. S., Bestland, E. A., Wells, R. T., & Krull, E. S. (2007). Palaeoenvironmental reconstruction of the late pleistocene to early holocene robertson cave sedimentary deposit, Naracoorte, South Australia. Australian Journal of Earth Sciences, 54(4), 541-559. doi:10.1080/08120090601078388

Scopus Eid


  • 2-s2.0-34249732565

Web Of Science Accession Number


Start Page


  • 541

End Page


  • 559

Volume


  • 54

Issue


  • 4

Place Of Publication


Abstract


  • Sedimentological investigations and geochemical analyses of the Robertson Cave deposit, 7 km south of Naracoorte, South Australia, document a palaeoenvironmental record for the Late Pleistocene and Early Holocene. Three distinct depositional episodes spanning the interval 32-8 ka are represented by over 4 m of sediments exposed in the chamber 2 excavation pit. The oldest of the three, the lower unit (>30 ka BP) is dominated by reddish and brown sandy silts. A 20 cm band of red silt horizons that cap this unit contain enriched ��15N values (12-15���), low C/N ratios, significant SO3 (20%) and CaO (18.5%) contents, a high alkyl-C component and phosphorus-rich mineralogy. These unique sediment horizons are interpreted as being derived from the accumulation of bat guano and degraded cave rock fragments. Their presence suggests a period of low sediment input into the cave, possibly reflecting the existence of a stable geomorphic environment prior to 30 ka. The time period 30-27 ka saw the rapid deposition of the middle unit, a sequence of coarser homogeneous sands that resulted in the entrance to chamber 2 becoming blocked. These horizon-less sediments, with clear aeolian features, are most likely representative of the drier conditions associated with the Last Glacial Maximum, which peaked at 20-17 ka. Deposition into the chamber recommenced at approximately 13 ka and continued until 8 ka, resulting in the accumulation of the upper unit, a sequence of silt, charcoal and organic matter rich horizons. Here, a shift to more 13C-depleted values (-25���to -27���) is evident in the bulk soil organic matter and charcoal between 11 and 10 ka, possibly reflecting a shift from the dry Last Glacial Maximum to the wetter environs of the Holocene. The upper unit may also be a record of burning practices associated with Aboriginal migration to the area.

UOW Authors


  •   Forbes, Matthew (external author)

Publication Date


  • 2007

Citation


  • Forbes, M. S., Bestland, E. A., Wells, R. T., & Krull, E. S. (2007). Palaeoenvironmental reconstruction of the late pleistocene to early holocene robertson cave sedimentary deposit, Naracoorte, South Australia. Australian Journal of Earth Sciences, 54(4), 541-559. doi:10.1080/08120090601078388

Scopus Eid


  • 2-s2.0-34249732565

Web Of Science Accession Number


Start Page


  • 541

End Page


  • 559

Volume


  • 54

Issue


  • 4

Place Of Publication