Proterozoicadj.n.

1887 S. F. Emmons Let. 25 May in Internat. Geol. Congr, Amer. Comm. Rep. (1891) a71 With Irving, Chamberlin and Walcott I think that the Huronian, Keweenawian, and Grand Cañon series, and whatever other clastic formations occur between the Cambrian and the Archean should be included in one grand group of equivalent rank with the Archean, Paleozoic, etc... I would suggest that the name Proterozoic should be given to this new group, signifying that its life was earlier than that of the other groups, without committing ourselves as yet to the statement that it was the first to appear upon the earth.

1892 U.S. Geol . Surv. Bull. 86 496 The newest Proterozoic or Algonkian rocks of different regions may stand in different positions.

1922 J. Y. Simpson Man & Attainm. Immortality x. 218 It is difficult..to speak with any confidence about those Proterozoic days.

1996 Sci. Amer. Jan. 64 (caption) An important growth spurt lasted from about 3.0 to 2.5 billion years ago, the transition between the Archean and Proterozoic eons.

1893 Jrnl. Geol. (Chicago) 1 675 In estimating for the Archean, Haughton included a large series of strata that are now placed in the Algonkian of the Proterozoic of the United States Geological Survey.

1905 T. C. Chamberlin & R. D. Salisbury Geol. I. i. 17 In these four great series of sedimentary rocks there are, here and there, intrusions of igneous rocks, and in some places the sedimentary beds have been metamorphosed into crystalline rocks by heat and pressure. This is particularly true in the lowest of these series, the Proterozoic, where a large part of the sediment is metamorphosed, and where there is much igneous rock.

1977 A. Hallam Planet Earth 189 The Proterozoic was, compared with the Archaean, dominantly a period of crustal reworking.

1993 Nature 21 Jan. 220/1 The Proterozoic may have witnessed the achievement of the multicellular grade of organization several times, and in quite unrelated lineages.