The fine versus coarse texture of eugeosynclinal versus miogeosynclinal appears to be true of other orogens. Although ophiolite-like assemblages are present, the crust in this part of the Canadian Shield did not rift enough to allow emplacement of new oceanic crust. Thus, the Labrador Trough is more akin to intracratonic basins like the Michigan Basin than to the Appalachians. It was a linear deposition basin that lay between the Archean Ungava craton on the west and the eastern continuation of the Churchill Province. As subsidence progressed slowly, a well-defined miogeosyncline formed on the west side, with a eugeosyncline of similar width on the east.
Sediments dominate the miogeosyncline, whereas volcanic rocks are predominant in the eugeosyncline.
These facies accumulated through most of the Aphebian Era of the Lower Proterozoic, and all rest on crystalline sialic basement of Archean gneisses. This converted the eastern zone into a large synclinorium with strong folding in the miogeosynclinal zone, compressing the trough to its present width of 80 to 120 km. High-angle thrusting is common in the western zone, in places producing repeated sequences, with eugeosynclinal units overriding westward. A major low-angle thrust forms a tectonic boundary between the geosynclinal facies.