Magnetic data processing and interpretation in the Passamaquoddy Bay Region of New Brunswick

Abstract

A marine and land magnetic survey had been conducted in the Passamaquoddy Bay region of southern New Brunswick in 1988. This thesis describes the processing and interpretation of the data using an IBM portable PC, Model 5155. The marine data required the design of a special processing technique because of an interference problem between the seismic equipment and magnetometer on the ship. This problem had left a series of spikes in the magnetic data. The first data processing step was therefore designed to remove the majority of the spikes from the data. Next, the data was compensated for the tow distance of the magnetometer behind the ship, corrected for diurnal variations in the geomagnetic field, and smoothed. Line profiles could then be plotted, allowing an interpretation to be made using MAGIX software. The most striking magnetic anomaly is associated with the Ministers Island Dyke. This body has a large magnetic susceptibility, making it easily visible on the magnetic profiles. A series of models of the dyke were calculated from several magnetic profiles. These models indicate a strike and dip of approximately 064° / 80° NW, and a thickness from a few metres to 18m. A possible fault is present northeast of Ministers Island, displacing the dyke.