CURRENT PRE-CAMBRIAN LITERATURE 743 
The Upper Marquette series is composed of the following forma- 
tions, from the base upward: The Ishpeming formation, the Michi- 
gamme formation, and the Clarksburg formation, in conformable 
succession. 
The Ishpeming formation includes two classes of rocks, which are 
called the Goodrich quartzite and the Bijiki schist. These rocks are 
sufficiently different to have different formation names, but the 
Bijiki schist for the west end of the district occupies a part of the 
horizon of the Goodrich quartzite in the central part. 
The Goodrich quartzite includes quartzites, micaceous quartz- 
schists, mica-schists, mica-gneisses, and at the base a basal conglom- 
erate. For the major part of the district this conglomerate rests 
upon the Negaunee formation, and the rock is an ore, chert, jasper, 
and quartz conglomerate. At a few places the Archean rocks are 
subjacent, and here their materials predominate in the conglomerate. 
The Goodrich quartzite is confined to the central and western parts 
of the district. For the major part of the district it rests unconform- 
ably upon the Negaunee formation. In places erosion has cut 
through the Negaunee formation into the Ajibik quartzite, and in a 
few cases even to the Archean, and here the Goodrich quartzite may 
be found resting on the lower formations. For the greater part of 
the area the Goodrich quartzite grades up into the Michigamme or 
Clarksburg formation, but in the northwestern part of the district it 
passes up into the Bijiki schist. The thickness is from 600. to 1550 
feet. 
The Bijiki schist is a banded griinerite-magnetite-schist, which has 
been derived by metasomatic and dynamic processes from an impure 
siderite. It is confined to the western part of the district. The Bijiki 
schist grades into the Goodrich quartzite below and into the Michi- 
gamme formation above. ‘The thickness is from zero to 520 feet. 
The Michigamme formation includes slates, graywackes, mica- 
schists, and mica-gneisses. The formation is exposed in a single 
large belt, running from the center to the western end of the district. 
It grades below into the Goodrich quartzite, Bijiki-schist, or Clarksburg 
formation. The thickness cannot be accurately estimated, but it is 
probably as much as 2000 feet. 
The Clarksburg formation is composed predominantly of volcanic 
materials, embracing basic lava flows, tuffs, ashes, and breccias, which 
locally are interleaved with or grade into slate, graywacke, or conglom- 
