New methods and technologies
Section editor – PhD in geology and mineralogy Prischepa O.M.
Article # 016
39 p.
New paleomagnetic method of borehole cores location determining
Geological study of large areas is based solely on the results of drilling. The relevance of such studies is obvious, as fields are very often found in closed areas. In such cases, the problem of sequence correlation of insufficiently faunistically characterized wells is common. Paleomagnetic (magnetostratigraphic) method is often the only method to enable such a correlation in these cases. However, it is necessary to find out the orientation of samples in the well in order to use paleomagnetic method. As for borehole cores, the orientation "top-bottom" is usually only known. The method that uses the direction of low-temperature (low-coercitive) modern viscous component of magnetization is applied in paleo-magnetism to orient the core samples to the cardinal. However, the possibilities of this method are limited for several reasons. We propose to use a new method that allows us to calculate the direction of the ancient magnetization components in those cases where conventional methods do not provide a satisfactory result. The new method was tested on the samples from two sequences of the Lower Vendian - Early Cambrian and one sequence of Cenozoic southeastern coastal of the White Sea area. The similarity of the results for natural outcrops and wells proves its high efficiency. The application of the new method has allowed us to calculate paleomagnetic poles for the Upper Vendian and Cenozoic Baltic as well as the age of reversal for the Late Vendian rocks. The alternative paleomagnetic poles for Vendian Baltic have been calculated through the results obtained and the reconstruction of paleogeographical position of the plate during the studied period of time has been made.
Key words: magnetostratigraphy, component composition of the rocks, Russian platform, correlation of geological sequences, core orientation.