ABSTRACT Obsidian Butte is an important lithic source for obsidian and artifacts from this location are distributed across archaeological sites in southern California and adjacent parts of northern Mexico. For this study, we used drill core material for infrared stimulated luminescence (IRSL) dating of potassium feldspar extracted from tuffaceous sediment directly underlying obsidian-bearing lava from Obsidian Butte. In addition, a core sample from lacustrine sediment below the tuffaceous sedimentary unit was dated by the same method. Stratigraphically consistent ages between 2.51 ± 0.32 kilo-annum (ka) (1 sigma uncertainty; average of two tuffaceous sediment samples) and 4.39 ± 0.49 ka (lacustrine sediment sample) were obtained. This constrains the eruption and earliest availability of the lithic resource of Obsidian Butte to 490 BCE (with uncertainty limits of ±320 years at ∼68 percent confidence, and ±640 years at ∼95 percent confidence). Since then, it would have been accessible during intermittent desiccation of Lake Cahuilla. This new date redefines obsidian from Obsidian Butte as a marker for the late prehistoric period.

中文翻译：

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通过红外激发发光对凝灰质沉积物中钾长石的测年，加利福尼亚州帝国县的黑曜石山年龄

摘要 Obsidian Butte 是黑曜石的重要石质来源，该地区的文物分布在加利福尼亚南部和墨西哥北部邻近地区的考古遗址中。在这项研究中，我们使用钻芯材料对从黑曜石小山含黑曜石熔岩直接下方的凝灰质沉积物中提取的钾长石进行红外受激发光 (IRSL) 测年。此外，采用相同方法对凝灰质沉积单元下方湖相沉积物的岩心样品进行了测年。获得了 2.51 ± 0.32 千年 (ka)（1 西格玛不确定性；两个凝灰质沉积物样本的平均值）和 4.39 ± 0.49 ka（湖泊沉积物样本）之间的地层一致年龄。这将 Obsidian Butte 的石质资源的喷发和最早可利用性限制在公元前 490 年（不确定性极限为 ±320 年，置信度为 68%，置信度为 ±640 年，置信度为 95%）。从那时起，在卡维拉湖间歇性干燥期间就可以访问它。这个新日期重新定义了黑曜石山丘的黑曜石作为史前晚期的标志。