U-series dating of soda straw stalactites from excavated deposits: method development and application to Blanche Cave, Naracoorte, South Australia

This study aimed to further test the method, reported by St Pierre et al. (2009), to develop robust chronologies of deposits in limestone caves through U/Th (Uranium/Thorium or U-Series) dating of soda straw stalactites. The chronology of fossil bearing deposits at Blanche Cave was further constrained with thermal ionisation mass spectrometry (TIMS) U/Th dating of 17 additional soda straw stalactite samples, and results were compared to recalibrated ¹⁴C ages of charcoal. The results support the assertion that soda straw stalactites can provide ages close to the time of sediment deposition and may be used as reliable chronological markers, particularly for periods reaching or beyond the radiocarbon dating limit. The application of an enhanced cleaning technique facilitated the reduction of detrital Th in samples, significantly increasing age accuracy and precision. Additionally U/Th age accuracy and precision was increased through the application of site-specific measured U/Th ratios to correct for the detrital ²³⁰Th component in samples.     

Expanding the utility of Uranium-series dating of speleothems for archaeological and palaeontological applications

Uranium-series (U-series) dating of speleothems is frequently used for palaeoclimate studies but its archaeological and palaeontological applications are limited to stratigraphically significant speleothem formations, such as flowstones, to provide maximum and minimum temporal points. This study targeted soda straw stalactites for U-series dating. In contrast to other speleothem formations, soda straw stalactites are fragile, have typically short life spans (usually only years but rarely up to a few hundred years) and are frequently incorporated into cave deposits. Results of thermal ionisation mass spectrometry (TIMS) U-series dating of soda straw stalactites from palaeontological excavations at Blanche Cave, South Australia, show that small, dense, clean straws tend to yield ages closest to the time of stratigraphic deposition. A correlation between soda straw U-series ages and radiocarbon ages of charcoal from the site is shown. Multiple soda straw age determinations for a single stratigraphic unit are required in order to verify age concordance. In conjunction with other dating methods, U-series dating of soda straw stalactites may help to significantly constrain the age of stratigraphic units and associated archaeological and palaeontological deposits in order to provide more robust chronologies. Here we advocate the collection of soda straw stalactites at future excavations of limestone cave sites.     

Information et espace public

Revue de Synthèse - Depuis une vingtaine d'années, les spécialistes de la littérature du XVIIIe siècle ont accordé une attention croissante à l'étude...     

试论20世纪60-70年代的河北环境保护

20世纪 6 0— 70年代 ,随着资源开发的迅速扩大和工业化的快速发展 ,河北省的环境破坏不断加重 ,环境污染开始产生并呈扩展之势。由于缺乏环境意识和缺乏环境保护科学知识 ,河北省的生态环境处于边恢复、边保护、边破坏的状况。环境、生态平衡等问题日益突出。环境污染和区域性干化加剧成为河北省区域性生态环境恶化的两大突出问题 ,而且直接影响和制约着河北经济发展和人民生活、生存条件。本文试对这一时期河北环境保护的历史进行梳理和探讨 ,总结其得失与经验教训。