Within the last few years, they have been called the
Algonkian Series, and later I shall speak of them more freely.
Prior to the deposition of these Algonkian strata, the Laurentian rocks
(the granite) upon which they rest were subject to a long period of
"planation," - as the grinding down and leveling of rock surfaces is termed.
After this planation was complete, a subsidence occurred; the whole area
became the bed of an inland sea, and upon the planed-down granite, the
debris that formed the Algonkian strata was washed.
While they were being deposited, the whole region was the scene of several
seismic and volcanic disturbances, for great dykes and "chimneys" of lava
are found, showing clearly that, by some means or other, the strata were
broken and shattered, cracked and seamed, and that through these cracks the
molten lava oozed - forced up from the interior of the earth. It spread out
over the Algonkian rocks in small sheets or blankets, which here and there
are still to be found to-day.
Tilting of the Algonkian Strata. Slowly this twelve thousand feet of strata
emerged into the sunlight. In the uplifting processes, the surface of the
earth, where they were, became tilted, and these strata therefore "dipped"
or "tilted" away from the perpendicular.
