Geomorphology of the Stromness Bay-Cumberland Bay Area, South Georgia
Geomorphology of the Stromness Bay-Cumberland Bay Area, South Georgia
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南乔治亚州斯特罗姆内斯湾-坎伯兰湾地区的地貌
DOI：
10.1017/s0016756801005039
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发表时间：
1971
影响因子：
2.3
通讯作者：
C. Clapperton
中科院分区：
文献类型：
--
作者：
C. Clapperton
马里恩岛是南大洋一座年轻的板内盾状火山，通常被认为是地幔柱的位置。对37个所谓的老灰色玄武岩全岩样品进行了新的K-Ar年龄测定，其年龄范围为450±10 ~ 130 ka。这些熔岩非常新鲜，而且是全晶质的，似乎是测定年代的理想材料。两个几乎垂直的剖面所测得的年龄与地层学的结果雅阁，相对年龄关系没有疑问。第三部分给出了异常年龄，表明存在遗传或过量的放射成因氩。这对于海洋岛屿上的陆上气流是极不寻常的。因此，我们敦促谨慎接受K-Ar年龄的样品没有地层控制。在过去的50万年里，马里恩的火山活动可能基本上是连续的，但根据当地的不整合面和测量年龄之间的差距，它被认为更有可能是偶发的。大约在450、350、240、170、110、85、50和<10 ka前的8个喷发活动期可以不同程度的置信度区分出来。根据海洋氧同位素记录，与熔岩互层的冰川沉积物可与更新世第2、4、6、8和12期冰期相对应。有迹象表明，至少有一些早期的火山活动与冰川阶段相吻合，但最近的两个事件，包括全新世一直延续到现在，显然是间冰期。
Marion Island is a youthful intraplate shield volcano in the Southern Ocean, generally considered to represent the location of a mantle plume. New K–Ar age determinations on 37 whole rock samples of so-called older grey basalt from the island range from 450±10 to ∼30 ka. The lavas are remarkably fresh and holocrystalline, appearing to be ideal for dating. The age results from two almost vertical sections, where relative age relationships are not in doubt, are in accord with the stratigraphy. A third section gave aberrant ages that indicate the presence of inherited or excess radiogenic argon. This is highly unusual for subaerial flows on an oceanic island. We therefore urge caution in accepting K–Ar ages on samples without stratigraphic control. Volcanic activity on Marion could have been essentially continuous during the last half million years but on the basis of local unconformities and gaps between the measured ages it is considered more likely to have been episodic. Eight periods of effusive activity at approximately 450, 350, 240, 170, 110, 85, 50 and <10 ka ago can be distinguished with varying degrees of confidence. Glacigene deposits that are intercalated with the lavas can be correlated with glacial stages 2, 4, 6, 8 and 12 of the Pleistocene time scale based on the marine oxygen isotopic record. Indications are that at least some of the earlier volcanic activity coincided with glacial stages but the two most recent episodes, including the Holocene one extending up to the present, are clearly interglacial.