Isotopic age determinations on precambrian rocks of the carpentaria region, Northern territory, Australia
作者:
I. McDougall,
P. R. Dunn,
W. Compston,
A. W. Webb,
J. R. Richards,
V. M. Bofinger,
期刊:
Journal of the Geological Society of Australia
(Taylor Available online 1965)
卷期:
Volume 12,
issue 1
页码: 67-90
ISSN:0016-7614
年代: 1965
DOI:10.1080/00167616508728586
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
A sequence up to 40,000 ft thick of unmetamorphosed and only slightly deformed sedimentary and volcanic rocks occurs in the Carpentaria Province of Northern Australia. Metamorphic and granitic rocks form the basement to this sequence, and K‐Ar and Rb‐Sr age measurements show that the basement granites are about 1,800 ± 50 m.y. old. Associated in space and time with the granitic rocks are acid volcanics which form the basal unit in the overlying sequence. Glauconites in sedimentary rocks from this succession yield dates ranging from 1,600 m.y. in the Tawallah Group, the second lowest unit, to about 1,390 m.y. in the Roper Group, the uppermost unit. Plagioclase and pyroxene from dolerites intrusive into the Roper Group give K‐Ar dates ranging from 1,100 to 1,280 m.y.; the older date provides a younger limit to the age of the Roper Group. Following slight folding the Wessel Group was deposited unconformably on the Roper Group; a single glauconite from the topmost formation of the Wessel Group yields concordant Rb‐Sr and K‐Ar dates of 780 ± 20 m.y.
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