REGIONAL FOLD GEOMETRY OF THE MEGUMA TERRANE, NS USING GEOLOGICAL AND GEOPHYSICAL TECHNIQUES WITH APPLIED GEOMATICS

Folds are commonly accompanied by thrusts in deformed low- to medium-grade sedimentary belts. The Acadian fold belt affecting the Meguma Supergroup (comprising the slaty Halifax and sandy Goldenville groups) in south mainland Nova Scotia, lacks thrusts.

As a preliminary step to address why folds predominate in the Acadian fold belt, the basic geometry of the folds must be established. To achieve this, a database of digitally available geological and geophysical data has been compiled.

There are three key uses for the database:

1) To observe relationships between the lithological, structural and geophysical data;

2) To extrapolate the fold structures across the study area between data sets; and, most importantly,

3) To construct structural-geophysical maps to aid construction of balanced cross-sections that will constrain the geometry of the Acadian fold belt down to the inferred detachment.

The construction of balanced sections requires a minimum of two bed units (markers), however there is only one mapped marker in the Acadian fold belt, the Halifax-Goldenville boundary. Nevertheless, the presence of a consistent pattern of magnetic anomalies within the sandy Goldenville Group suggests that construction of a “virtual” second marker may be a viable option. In detail, the pattern of anomalies consists of several discrete, continuous anomalies that suggest the presence of sulphide-rich, slaty beds within the Goldenville. Surprisingly, these discrete anomalies correlate with lithologies within the Goldenville illustrated on the cross-sections (but not mentioned in the map legends) of E.R. Faribault (Faribault, 1893-1909). Like other sulphide-rich, slaty units in the Meguma Supergroup these inferred units would generate high magnetic anomalies. Geophysical modeling of Faribault’s geological sections utilizing the inferred slaty units interlayered within the sandy Goldenville produces calculated magnetic anomaly patterns similar to the observed. Use of this “virtual” marker together with the Halifax-Goldenville boundary, allows for construction of balanced sections.

Faribault, E.R., 1893-1909, GSC, Map Nos. 28, 37-41, 48-55, 67-8, scale 1 inch to 1 mile.