Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

Geological Magazine

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (15) Citing Articles via Google Scholar Google Scholar Articles by McDOUGALL, I. Articles by CHEVALLIER, L. Search for Related Content GeoRef GeoRef Citation

K–Ar geochronology of Marion Island, Southern Ocean

IAN McDOUGALL^*,*, WILHELM VERWOERD and LUC CHEVALLIER^,

^* Research School of Earth Sciences, The Australian National University, Canberra A.C.T. 0200, Australia
Department of Geology, University of Stellenbosch, Private Bag X1, Matieland 7602, Republic of South Africa

^* Author for correspondence: Ian.McDougall{at}anu.edu.au

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.

This article has been cited by other articles:

				S. L Chown and P. Convey Spatial and temporal variability across life's hierarchies in the terrestrial Antarctic Phil Trans R Soc B, December 29, 2007; 362(1488): 2307 - 2331. [Abstract] [Full Text] [PDF]

				T. Imaoka, T. IMAOKA, and T. ITAYA K-Ar geochronology of a middle Miocene submarine volcano-plutonic complex in southwest Japan Geological Magazine, January 1, 2004; 141(1): 1 - 13. [Abstract] [Full Text] [PDF]

				R. V. Dingle and R.V. Dingle Some palaeontological implications of putative, long-term, gene reactivation Journal of the Geological Society, September 1, 2003; 160(5): 815 - 818. [Abstract] [Full Text] [PDF]