Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.662498
Title: Palaeomagnetic secular variation studies on Holocene lake sediments
Author: Stober, Julie C.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1978
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Abstract:
Cores of sediment were collected from six lakes in southern and eastern Finland. Measurements of the natural remanent magnetization (PIRM) and the magnetic susceptibility were made on both the unopened cores and on subsamples in order to define secular variation curves for Finland. Tests showed the remanence to be stable. Age estimates were obtained from pollen analyses since radiocarbon dating of the sediments proved to be unsatisfactory. The correlation between cores from any one lake was facilitated by use of the intensity and susceptibility logs. Swings in both the declination and inclination records obtained from the cores were correlatable within and, to some extent, between lakes. Using a variety of magnetic methods it was concluded that fine grained magnetite carried the PIR14 of the sediments. Haematite was present in some of these sediments but did not appear to carry any of the 11RbL. It was found that the HR14 was decreased by drying and by cooling through -10°C. In both cases randomization of fine grains which carried the HR14, brought, about by physical changes in the sediment, was responsible for the loss of intensity. Rotation of magnetic grains after deposition of the sediment appeared to be the main mechanism by which the lake sediments acquired an HRM. Further experiments showed that the grains were not fixed in place simply by dewatering of the sediments but that the growth of gels in the sediment stabilized the particles. Some grains in the sediments were still free to rotate and to acquire a remanence. Samples of bedrock, soil, drift and stream sediment were collected from the catchmeat areas and magnetic measurements made on them to determine the source of the magnetic minerals in the lake sediments. The measurements indicated that the magnetic minerals were derived from the glacial drift. Haematite was present as a secondary mineral in the drift but was broken down during erosion and transport of detritus to the lakes.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.662498  DOI: Not available
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