40Ar/39Ar dating of the Kapthurin Formation, Baringo, Kenya
40Ar/39Ar dating of the Kapthurin Formation, Baringo, Kenya
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DOI：
10.1006/jhev.2001.0517
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发表时间：
2002-01-01
影响因子：
3.2
通讯作者：
McBrearty, S
中科院分区：
文献类型：
--
作者：
Deino, AL;McBrearty, S
40Ar/39Ar放射性测年技术已被应用于肯尼亚裂谷图根山Kapthurin组的凝灰岩和熔岩。利用40Ar/39Ar技术的两种不同形式，单晶全熔融和激光增量加热，确定了该组内5个标志层的年代：在底部附近，卡苏林玄武岩为0.61±0.04 Ma；浮石凝灰岩为0.543±0.004 Ma；上卡苏林玄武岩为0.552±0.015 Ma；灰色凝灰岩为0.509±0.009 Ma；在地层上部，层状凝灰岩为0.284±0.012 Ma。浮岩凝灰岩的新的、精确的放射性年龄测定也为分布广泛的巴林戈湖粗面岩提供了一个年龄，因为浮岩凝灰岩是这次巨大粗面岩喷发的早期火山碎屑阶段。这些结果确定了化石古人类KNM-BK63-67和KNM-BK8518的年龄约为0.510-0.512 Ma，这是一个重要的发现，因为很少有中更新世的古人类被放射性测年。因此，Kapthurin原始人与来自博多、埃塞俄比亚和坦桑尼亚的原始人几乎是同时代的。地层下部湖相沉积形成的片状和核心工业受到0.55-0.52 Ma新日期的限制，在此期间，以手斧为特征的阿舍利工业在整个东非广为人知。在卡普图林组沉积中发现了典型的中石器时代的斑点，其年代为0.509+/-0.009 Ma至0.284+/-0.012 Ma之间。这一日期比之前对东非其他地区MSA年龄的估计高出49ka，并确定了该区域从Acheulian到MSA的过渡年龄。在此期间，还出现了使用勒瓦卢瓦技术制造小薄片和双面预制件、系统地生产刀片以及使用和加工红色赭石的证据。在这个深度出现刀片和红色赭石是很重要的，因为刀片象征着高度的技术能力，而红色赭石则意味着象征性的行为。(C)2002年学术出版社：40Ar/39Ar辐射测年技术已应用于肯尼亚裂谷图根山Kapthurin组的凝灰岩和熔岩。利用40Ar/39Ar技术的两种不同形式，单晶全熔融和激光增量加热，确定了该组内5个标志层的年代：在底部附近，卡苏林玄武岩为0.61±0.04 Ma；浮石凝灰岩为0.543±0.004 Ma；上卡苏林玄武岩为0.552±0.015 Ma；灰色凝灰岩为0.509±0.009 Ma；在地层上部，层状凝灰岩为0.284±0.012 Ma。浮岩凝灰岩的新的、精确的放射性年龄测定也为分布广泛的巴林戈湖粗面岩提供了一个年龄，因为浮岩凝灰岩是这次巨大粗面岩喷发的早期火山碎屑阶段。这些结果确定了化石古人类KNM-BK63-67和KNM-BK8518的年龄约为0.510-0.512 Ma，这是一个重要的发现，因为很少有中更新世的古人类被放射性测年。因此，Kapthurin原始人与来自博多、埃塞俄比亚和坦桑尼亚的原始人几乎是同时代的。地层下部湖相沉积形成的片状和核心工业受到0.55-0.52 Ma新日期的限制，在此期间，以手斧为特征的阿舍利工业在整个东非广为人知。在卡普图林组沉积中发现了典型的中石器时代的斑点，其年代为0.509+/-0.009 Ma至0.284+/-0.012 Ma之间。这一日期比之前对东非其他地区MSA年龄的估计高出49ka，并确定了该区域从Acheulian到MSA的过渡年龄。在此期间，还出现了使用勒瓦卢瓦技术制造小薄片和双面预制件、系统地生产刀片以及使用和加工红色赭石的证据。在这个深度出现刀片和红色赭石是很重要的，因为刀片象征着高度的技术能力，而红色赭石则意味着象征性的行为。(C)2002年学术出版社。
The 40Ar/39Ar radiometric dating technique has been applied to tuffs and lavas of the Kapthurin Formation in the Tugen Hills, Kenya Rift Valley. Two variants of the 40Ar/39Ar technique, single-crystal total fusion (SCTF) and laser incremental heating (LIH) have been employed to date five marker horizons within the formation: near the base, the Kasurein Basalt at 0.61 +/- 0.04 Ma; the Pumice Tuff at 0.543 +/- 0.004 Ma; the Upper Kasurein Basalt at 0.552 +/- 0.015 Ma; the Grey Tuff at 0.509 +/- 0.009 Ma; and within the upper part of the formation, the Bedded Tuff at 0.284 +/- 0.012 Ma. The new, precise radiometric age determination for the Pumice Tuff also provides an age for the widespread Lake Baringo Trachyte, since the Pumice Tuff is the early pyroclastic phase of this voluminous trachyte eruption. These results establish the age of fossil hominids KNM-BK 63-67 and KNM-BK 8518 at approximately 0.510-0.512 Ma, a significant finding given that few Middle Pleistocene hominids are radiometrically dated. The Kapthurin hominids are thus the near contemporaries of those from Bodo, Ethiopia and Tanzania. A flake and core industry from lacustrine sediments in the lower part of the formation is constrained by new dates of 0.55-0.52 Ma, a period during which the Acheulian industry, characterized by handaxes, is known throughout East Africa. Points, typical of the Middle Stone Age (MSA), are found in Kapthurin Formation sediments now shown to date to between 0.509 +/- 0.009 Ma and 0.284 +/- 0.012 Ma. This date exceeds previous estimates for the age of the MSA elsewhere in East Africa by 49 ka, and establishes the age of Acheulian to MSA transition for the region. Evidence of the use of the Levallois technique for the manufacture of both small flakes and biface preforms, the systematic production of blades, and the use and processing of red ochre also occurs in this interval. The presence of blades and red ochre at this depth is important as blades signify a high degree of technical competence and red ochre suggests symbolic behavior. (C) 2002 Academic Press.The 40Ar/39Ar radiometric dating technique has been applied to tuffs and lavas of the Kapthurin Formation in the Tugen Hills, Kenya Rift Valley. Two variants of the 40Ar/39Ar technique, single-crystal total fusion (SCTF) and laser incremental heating (LIH) have been employed to date five marker horizons within the formation: near the base, the Kasurein Basalt at 0.61 +/- 0.04 Ma; the Pumice Tuff at 0.543 +/- 0.004 Ma; the Upper Kasurein Basalt at 0.552 +/- 0.015 Ma; the Grey Tuff at 0.509 +/- 0.009 Ma; and within the upper part of the formation, the Bedded Tuff at 0.284 +/- 0.012 Ma. The new, precise radiometric age determination for the Pumice Tuff also provides an age for the widespread Lake Baringo Trachyte, since the Pumice Tuff is the early pyroclastic phase of this voluminous trachyte eruption. These results establish the age of fossil hominids KNM-BK 63-67 and KNM-BK 8518 at approximately 0.510-0.512 Ma, a significant finding given that few Middle Pleistocene hominids are radiometrically dated. The Kapthurin hominids are thus the near contemporaries of those from Bodo, Ethiopia and Tanzania. A flake and core industry from lacustrine sediments in the lower part of the formation is constrained by new dates of 0.55-0.52 Ma, a period during which the Acheulian industry, characterized by handaxes, is known throughout East Africa. Points, typical of the Middle Stone Age (MSA), are found in Kapthurin Formation sediments now shown to date to between 0.509 +/- 0.009 Ma and 0.284 +/- 0.012 Ma. This date exceeds previous estimates for the age of the MSA elsewhere in East Africa by 49 ka, and establishes the age of Acheulian to MSA transition for the region. Evidence of the use of the Levallois technique for the manufacture of both small flakes and biface preforms, the systematic production of blades, and the use and processing of red ochre also occurs in this interval. The presence of blades and red ochre at this depth is important as blades signify a high degree of technical competence and red ochre suggests symbolic behavior. (C) 2002 Academic Press.