The non-uniqueness of the Australian Mesozoic palaeomagnetic pole position
The non-uniqueness of the Australian Mesozoic palaeomagnetic pole position
复制标题
澳大利亚中生代古地磁极位置的非唯一性
DOI：
10.1111/j.1365-246x.1976.tb01274.x
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发表时间：
1976
影响因子：
2.8
通讯作者：
P. Schmidt
中科院分区：
文献类型：
--
作者：
P. Schmidt
总结
从塔斯马尼亚粗玄岩，Gingenbullen粗玄岩，前景粗玄岩，直布罗陀正长岩（所有以前检查超过十年前）和Garrawilla火山岩，Nombi喷出物和Glenrowan侵入岩（代表一个新的研究）获得的侏罗纪古地磁结果。对于某些岩层，早期的实验技术似乎未能完全去除次生成分。有证据表明，一个特别恶劣的风化期（可能在晚白垩世/早第三纪）可能是次生成分的部分原因。在交变磁场（AF）退磁过程中也检测到并消除了旋转反磁化（RRM）。来自塔斯马尼亚的粗粒岩的结果与先前发表的结果非常一致，而来自其他重新调查的结果则与早期结果有明显不同。根据这些和其他最近的数据，澳大利亚中生代古地磁极位置的一个新的解释。三叠纪（52° S，153° E）、侏罗纪（47° S，176° E）和白垩纪（53° S，152° E）的平均极点位置现在被认为是分开的。根据古地磁资料，提出了塔斯马尼亚粗玄岩的年龄分布，并将冈瓦纳大陆东部的裂解年龄限定在100 ~ 160万年前。澳大利亚侏罗纪极的位置进行了比较，晚三叠世-中侏罗世古磁极从其他南部的土地和印度在其predrift配置所决定的地貌重建。结果表明，这些极在63° S，71° E（A95= 3°）的平均极位附近形成一个紧密的极群。
Summary
Palaeomagnetic results for the Jurassic obtained from the Tasmanian dolerites, the Gingenbullen dolerite, the Prospect dolerite, the Gibraltar syenite (all previously examined over a decade ago) and the Garrawilla volcanics, the Nombi extrusives and the Glenrowan intrusives (representing a new study) are presented. It appears that for some rock formations early experimental techniques failed to remove completely secondary components. Evidence suggests that a particularly harsh period of weathering (probably during the Late Cretaceous/Early Tertiary) may be partly responsible for secondary components. Rotational remanent magnetization (RRM) has also been detected and eliminated during alternating field (AF) demagnetization procedures. The results from the Tasmanian doleraites are in close agreement with the previously published results, while those from the other reinvestigations are seen to be markedly different from the early results. In the light of these and other recent data, a new interpretation of the Australian Mesozoic palaeomagnetic pole position is given. The mean Triassic (52° S, 153° E), Jurassic (47° S, 176° E) and Cretaceous (53° S, 152° E) pole positions are now considered as separate. On the basis of the palaeomagnetic data, a spread in age for the Tasmanian dolerite is suggested and the age of the breakup of eastern Gondwanaland is constrained between 100 and 160 My ago. The Australian Jurassic pole position is compared to the Late Triassic–Middle Jurassic palaeomagnetic poles from other southern lands and India in their predrift configuration as dictated by geomorphological reconstructions. It is shown that these poles form a tight group around their mean pole position at 63° S, 71° E (A95= 3°) with respect to present day Africa.