Lakehead University Geology - Journal Yearbook (Thunder Bay, Ontario Canada)

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Dr. John S. Mothersill. B.Sc.. B.Sc.. Ph.D. Background; Exploration Geologist for Standard Oil (N.J.) Senior Geologist for Mobil International Oil Co. Exploring for petroleum in Turkey, Nigeria, France and Colombia, 1956-64 Associate Professor, Lakehead University, since 1966 Dean of Science at Lakehead since 1975. During June, four Alpine piston cores were taken of the sedimentary sequence in the main post-glacial basin of Thunder Bay from a Deep Diving Systems drilling barge. The locations of the cores were picked so that in- creasingly thicker post-glacial sections would be encountered from the basin margin toward the basin centre. All four cores consisted of the underlying glacial varved section. Seven hundred and eighty— four oriented, two— cm samples were taken from along the length of three of the cores (at 3 cm intervals throughout the post-glacial section and at 10 cm intervals throughout the varved section). The declination, inclination, intensity and susceptibility of magnetization and Q ratio (intensity susceptibility) of each sample was determined using paleomagnetic equipment at the University of Edinburgh. These data were plotted by computer programme and the declination direction variations were correlated for the two thicker post-glacial section cores. For the post- glacial section, five major swiggs occur in declination; the inclination variation is in the order of 35 ; and the susceptibility shows two slight but significant shifts. The uppermost susceptibility shift appears to cor- respond to the time of the Nipissing phase based on radiocarbon age deter- minations. Substantial decreases in the intensity and susceptibility of magnetization were noted for the sediments at the base of the post-glacial section. Paleomagnetic directions also were determined after the samples were cleaned in a peak field of 200 oersteds to get rid of any extraneous NRM directions. The declination and inclination determinations of the cleaned samples correspond almost identically with the results obtained from the un- cleaned samples. Radiocarbon analyses are being carried out on fifteen samples from two of the cores to determine the age of the declination and inclination swings and susceptibility shifts. This age-dated paleomagnetic column will be used for time-parallel correlations throughout the northern and western Lake Superior area. Post-glacial sediments in this basin should provide a continuous or near continuous sedimentary record to assess sed- imentation rates and climate changes. Presently, sedimentation rates are being assessed by; a) determinations, b) the variability of the organic C N content of the samples after treatment with sulphurous acid using a Perkin- Elmer CRN Analyzer and c) grain-size variability using the Micromeritics Sedigraph 5000 method. These data are presently being compiled. During the summer, a report in methodology for determining asbestos fibre counts Irl water was finalized in conjunction with co-workers from sev- eral other laboratories in the province. The method will be recommended to the Ministry of the Environment (Ontario) as the standard method for determining asbestos fibre counts in water.