Call number:
ZSP-164-39
In:
Scientific reports
Description / Table of Contents:
A study has been made of the remanent magnetism of more than 400 samples collected from 104 localities in Graham Land and several of the nearby islands. The directions of the remanent magnetism of these samples have been measured and analysed in the standard manner. The stability of the magnetism has been investigated by tests involving the storage of specimens and their partial demagnetization in alternating magnetic fields. The study was restricted to the investigation of igneous rocks as the few sediments available for collection were found to be too weakly magnetic to be measurable. The magnetism of Tertiary and Recent lavas, collected from 12 localities, and of Andean intrusive rocks (late Cretaceous to early Tertiary age) from another 12 localities, is aligned on average along the axial gecentric dipole field direction, but both normally and reversely magnetized rocks have been found. The stability and the dispersion of magnetic directions indicate the remanent magnetism was probably acquired when the rocks were first formed. The magnetism of the Upper Jurassic Volcanic Group and the older intrusives (?Lover Palaeozoic) has been found to be either unstable or widely scattered in direction. It is suspected that the intrusion of the Andean suite so affected all the pre-existing rocks as to destroy their original magnetism. From these results it is possible to infer the condition of the Earth's past magnetic field only in connection with the Andean and younger rocks. This is that the Earth's magnetic field in the region of Graham Land has been, on average, in the same direction as the axial geocentric dipole field, or its exact reverse, since the intrusion of the Andean suite. Unfortunately there is no information from pre-Andean rocks in this area that can be used for comparison with the interesting results obtained elsewhere in Antarctica.
Type of Medium:
Series available for loan
Pages:
24 S.
Series Statement:
Scientific reports / British Antarctic Survey 39
URL:
http://www.antarctica.ac.uk/about_bas/publications/scientific_reports/index.php
Branch Library:
AWI Library
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