The Australian Archaeomagnetism Laboratory, Department of Archaeology and History, La Trobe University, Wurundjeri Country, VIC, Australia.
Geoarchaeology and Archaeometry Research Group, Southern Cross University, Lismore, NSW, Australia.
PeerJ. 2024 Jun 28;12:e17478. doi: 10.7717/peerj.17478. eCollection 2024.
Bolt's Farm is the name given to a series of non-hominin bearing fossil sites that have often been suggested to be some of the oldest Pliocene sites in the Cradle of Humankind, South Africa. This article reports the results of the first combined Uranium-Series and Electron Spin Resonance (US-ESR) dating of bovid teeth at Milo's Cave and Aves Cave at Bolt's Farm. Both tooth enamel fragments and tooth enamel powder ages were presented for comparison. US-ESR, EU and LU models are calculated. Overall, the powder ages are consistent with previous uranium-lead and palaeomagnetic age estimates for the Aves Cave deposit, which suggest an age between ~3.15 and 2.61 Ma and provide the first ages for Milo's Cave dates to between ~3.1 and 2.7 Ma. The final ages were not overly dependent on the models used (US-ESR, LU or EU), which all overlap within error. These ages are all consistent with the biochronological age estimate (<3.4->2.6 Ma) based on the occurrence of Stage I . Preliminary palaeomagnetic analysis from Milo's Cave indicates a reversal takes place at the site with predominantly intermediate directions, suggesting the deposit may date to the period between ~3.03 and 3.11 Ma within error of the ESR ages. This further suggests that there are no definitive examples of palaeocave deposits at Bolt's Farm older than 3.2 Ma. This research indicates that US-ESR dating has the potential to date fossil sites in the Cradle of Humankind to over 3 Ma. However, bulk sample analysis for US-ESR dating is recommended for sites over 3 Ma.
博尔特农场是一系列非人类化石遗址的名称，这些遗址常被认为是南非人类摇篮中最古老的上新世遗址之一。本文报告了首次对博尔特农场米洛洞和鸟类洞的牛科牙齿进行铀系列和电子自旋共振（US-ESR）联合定年的结果。两种牙齿珐琅质碎片和牙齿珐琅质粉末年龄都被提出以供比较。US-ESR、EU 和 LU 模型都进行了计算。总体而言，粉末年龄与鸟类洞沉积物以前的铀铅和古地磁年龄估计一致，这些估计表明年龄在3.15 至 2.61 Ma 之间，并为米洛洞日期提供了第一个年龄，在3.1 至 2.7 Ma 之间。最终年龄并不过于依赖所使用的模型（US-ESR、LU 或 EU），所有模型的年龄都在误差范围内重叠。这些年龄都与生物年代学年龄估计（<3.4-2.6 Ma）一致，这一估计基于 I 期的发生。来自米洛洞的初步古地磁分析表明，该遗址发生了反转，主要是中间方向，这表明该沉积物的年代可能在~3.03 至 3.11 Ma 之间，误差与 ESR 年龄一致。这进一步表明，在博尔特农场，没有明确的 3.2 Ma 以前的古洞穴沉积物的例子。这项研究表明，US-ESR 定年有可能将人类摇篮中的化石遗址定年到 3 Ma 以上。然而，对于 3 Ma 以上的遗址，建议进行 US-ESR 定年的批量样本分析。
