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A geological cross-section showing the principal tectonostratigraphic units of the Trans-Hudson Orogen. It is based on seismic reflection profiles (whose locations, lines 2, 3 and 9, were shown in the previous slide), as well as on geological information obtained at the surface and from drill cores, and on potential field maps. The stippled lines indicate in a schematic fashion the dip and frequency of seismic reflections.

LITHOPROBE's seismic cross sections show a THIRD Archean craton to be present (purple blob above “Reflection Moho”), over which the overlying rock layers were pushed and shoved and now drape, to the west on its west side, to the east on its east side. (See the schematic cross section shown on the screen.) This discovery of a formerly unsuspected, additional Archean remnant between the Superior and Hearne-Rae cratons, and within the general THO domain, came as a complete surprise to the geoscientists. Although hidden underground from direct view there are several "basement windows" in the Glennie Domain which may belong to the same, newly discovered craton.
This find in central Saskatchewan's underground also has a deep crustal root, as is expressed in the local thickness of the crust, whose base is defined by the (seismic) Mohorovicic discontinuity, or "Moho" for short. (See the lowest unit in the schematic cross section.) The question now is how far this third Archean block extends to the north and south. Is it an ancient microcontinent, does it connect somewhere? Diamond hunters are interested in this find in that wherever the crust is thick and Archean, the potential for diamonds is great. Kimberlite occurrences (the volcanic pipes which are potential sites for diamonds) appear to be associated with this Archean block.

We want to remember the assembly of THO, the map showing the tectonic units, and the schematic cross section which crosses them to give us a 3D image. This is because at the same time the THO came about through continental collisions, the same happened over the area which now underlies Alberta. It seems to have been a more or less simultaneous (or coeval) series of events, a sort of double billing, with two large mountain belts having been formed side by side, as it were, separated only by the Hearne Province, which itself was deformed and imbricated (different slices of it thrust on intermingled, thereby forming a stack).

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