Post by Surroundx on Jun 27, 2015 16:17:33 GMT 10
Re-evaluating the Late Quaternary fossil mammal assemblage of Seton Rockshelter, Kangaroo Island, South Australia, including the evidence for late-surviving megafauna
Abstract
It is widely accepted that most larger Australian vertebrates were extinct by 40 ka. The reliability of <20-ka radiocarbon (14C) ages on charcoal stratigraphically associated with sthenurine (short-faced) kangaroo tooth fragments from Seton Rockshelter, Kangaroo Island, have therefore proven contentious. Some researchers have argued these fossils were in situ, while others have claimed they were reworked. To address this we obtained new 14C ages on bones from the site. These bone ages are not only consistent with earlier charcoal ages, but are in near-perfect stratigraphic order, providing strong support for the site's stratigraphic integrity. Our analyses indicate units aged 21−17 ka were primarily accumulated by Tasmanian devils (Sarcophilus harrisii) and owls (Tyto species), after which humans became the primary accumulation agent. The tight chronology, faunal trends and current lack of evidence for older layers from which specimens could have been reworked suggest the sthenurine remains may be in situ. However, because attempts to directly date sthenurine material failed, we cannot confidently assert that they survived to this time. Therefore, Seton Rockshelter may be best excluded from the Pleistocene extinction debate until the site can be re-excavated and more conclusive evidence collected, including more complete or directly datable sthenurine remains.
Source:
McDowell, M. C. et al. (2015). Re-evaluating the Late Quaternary fossil mammal assemblage of Seton Rockshelter, Kangaroo Island, South Australia, including the evidence for late-surviving megafauna. Journal of Quaternary Science 30: 355–364. [Abstract]
Abstract
It is widely accepted that most larger Australian vertebrates were extinct by 40 ka. The reliability of <20-ka radiocarbon (14C) ages on charcoal stratigraphically associated with sthenurine (short-faced) kangaroo tooth fragments from Seton Rockshelter, Kangaroo Island, have therefore proven contentious. Some researchers have argued these fossils were in situ, while others have claimed they were reworked. To address this we obtained new 14C ages on bones from the site. These bone ages are not only consistent with earlier charcoal ages, but are in near-perfect stratigraphic order, providing strong support for the site's stratigraphic integrity. Our analyses indicate units aged 21−17 ka were primarily accumulated by Tasmanian devils (Sarcophilus harrisii) and owls (Tyto species), after which humans became the primary accumulation agent. The tight chronology, faunal trends and current lack of evidence for older layers from which specimens could have been reworked suggest the sthenurine remains may be in situ. However, because attempts to directly date sthenurine material failed, we cannot confidently assert that they survived to this time. Therefore, Seton Rockshelter may be best excluded from the Pleistocene extinction debate until the site can be re-excavated and more conclusive evidence collected, including more complete or directly datable sthenurine remains.
Source:
McDowell, M. C. et al. (2015). Re-evaluating the Late Quaternary fossil mammal assemblage of Seton Rockshelter, Kangaroo Island, South Australia, including the evidence for late-surviving megafauna. Journal of Quaternary Science 30: 355–364. [Abstract]
