Stratigraphy of the upper Neoproterozoic Kango and lower Palaeozoic Table Mountain groups of the Cape fold belt revisited
Stratigraphy of the upper Neoproterozoic Kango and lower Palaeozoic Table Mountain groups of the Cape fold belt revisited
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重新审视开普褶皱带上新元古代坎戈和下古生代桌山群的地层学
DOI：
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
M. Wit
中科院分区：
文献类型：
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作者：
W. Barnett;R. Armstrong;M. Wit
南非开普弗尔德带最古老的岩石暴露在几个岩浆中。这些内部沉积物主要由低品位的变质沉积物组成。这些沉积物的年龄被认为是新元古代晚期。Kango Inlier的地层(在Oudthoorn附近，在好望角褶皱带的东西走向的南部分支内)被细分为两个序列--Goegamma和Kansa亚群，由一个明显的不整合相互分隔。SHRIMP II碎屑锆石U/Pb同位素测年结果表明，中元古代纳马卡-纳塔尔省片麻岩(约1100 Ma)可能是戈加玛亚群的沉积源区，纳马卡-纳塔尔活动带和开普花岗岩套岩石都是年轻堪萨亚群(碎屑锆石=518+或-9 Ma)底部的沉积物来源。这些年龄表明，堪萨亚群的年龄为中寒武世(或更年轻)，并可能与沿开普敦褶皱带西支暴露的Klipheuwel群相关联。此外，这两个亚群之间的不整合代表了一个主要的EO-寒武纪间断，应该被认为是分隔海角超群与下伏的新元古代-早寒武世变质沉积的主要层序界面。堪萨亚群可能代表了桌山群之下的机械裂谷序列，而桌山群又代表了冈瓦那南部早古生代被动裂谷边缘的热沉降期。
The oldest rocks of the Cape Fold Belt of South Africa are exposed in several inliers. These inliers are comprised predominantly of low-grade metasediments. The age of the sediments is thought to be late Neoproterozoic. The stratigraphy of the Kango inlier (near Oudtshoorn, within the southern, east-west-striking branch of the Cape Fold Belt) has been subdivided into two successions--the Goegamma and Kansa Subgroups, separated from one another by a clear unconformity. U/Pb isotope dating of detrital zircons, using the SHRIMP II, indicates that the gneisses of the Mesoproterozoic Namaqua-Natal Province (c. 1100 Ma) are the probable sediment source terrain for the Goegamma Subgroup, and that both the Namaqua-Natal Mobile Belt and rocks from the Cape Granite Suite are sources for the sediments at the base of the younger Kansa Subgroup (detrital zircons = 518+ or -9 Ma). These ages suggest that the Kansa Subgroup is Mid-Cambrian in age (or younger) and could be correlated with the Klipheuwel Group exposed along the western branch of the Cape Fold Belt. Furthermore, it is suggested that the unconformity between the two subgroups represents a major Eo-Cambrian hiatus and should be considered as a major sequence boundary separating the Cape Supergroup from the underlying Neoproterozoic-Early Cambrian metasediments. The Kansa Subgroup possibly represents the mechanical rift succession underlying the Table Mountain Group that in turn, represents the thermal subsidence phase of an Early Palaeozoic passive rift margin of southern Gondwana.