The geological history of the state covers the period from Algonkian to late Carboniferous time, after which there is a gap in the record until Tertiary time, except that there was apparently a temporary depression of the north-western and southwestern corners in the Cretaceous age.
Regarding now the outcrops of bed-rock, there are exposures of Algonkian (doubtful, and at most a mere patch on Pilot Knob), Archean, Cambrian, Ordovician, Silurian, Devonian, sub-Carboniferous and Carboniferous.
The remainder of Finland is built up of the oldest known crystalline rocks belonging to the Archaeozoic or Algonkian period.
Prolerozoic (Algonkian) Systems.The Proterozoic group of rocks (called also Algonkian) includes all formations younger than the Archean and older than the Palaeozoic rocks.
He wrote Correlation Papers - Archaean and Algonkian (1892), Some Principles Controlling the Deposition of Ores (1901).