In 1928, 1929, and 1932 the writer made a study of the Abram series— a “Timiskaming-type” series of early pre-Cambrian age—which has a widespread distribution in northwestern Ontario.1 The most characteristic feature of this series is a thick conglomerate of terrestrial origin. Associated with these coarse clastics are graywackes, siltstones, argillites, iron-bearing formation, and tuffs. It is the purpose of this paper to describe in greater detail the banded argillites, which were restudied in 1934,2 to discuss further their probable origin, and to place on record some pre-Cambrian varve-thickness measurements.
The slates with the most perfect banding are exposed on the islands and mainland of East Bay of Minnitaki Lake, district of Kenora, in northwestern Ontario (Fig. 1). The stratigraphy of this area has been imperfectly known, owing to the complex nature of the structure in which the slates and associated strata are . . .