372 PRE-CAMBRIAN NORTH AMERICAN LITERATURE 
Walcott* gives the results of his study of the Algonkian rocks of the Grand 
Canyon of the Colorado. The following classification of the rocks is adopted : 
Cambrian Tonto 
= Vinearmiorrrnnisy— : 
\ Chuar 
Algonkian Grand Canyon - 
/ Unkar 
—Great Unconformity 
Algonkian (?) 1 Vishnu. 
The Vishnu at the one point examined, due south of Vishnu’s Temple, 
consists of micaceous schists and quartzites, cut by dikes and veins of granite. 
The Unkar terrane, 6830 feet thick, consists of limestones, sandstones, con- 
glomerates, and intrusive and extrusive basic rocks of various kinds. The 
basal conglomerate is formed largely of pebbles derived from the upturned 
edges of the pre-Unkar strata. The Chuar terrane, 5120 feet thick, consists 
mainly of shales of various kinds, but contains 285 feet of limestone. Resting 
unconformably upon the Grand Canyon series isthe Tonto Cambrian. Before 
the deposition of the latter the Grand Canyon series was planed to a base 
level, and all the strata of the series were truncated. 
Midway in the lower portion of the shales and limestones of the Chuar 
terrane the presence of fauna is shown by a minute discinoid or patelloid 
shell, a small Lingula-like shell (which may be a species of Hyolithes), and 
a fragment of what appears to be the pleural lobe of a segment of a trilobite 
belonging to a genus allied to the genus Olenellus, Olenoides or Paradoxides. 
There is also a Stromatopora-like form that is probably organic. 
The entire Grand Canyon series is placed in the Algonkian period or 
Proterozoic era. Various possible correlations of the Grand Canyon with 
other series may be made, but it is evident that until characteristic fossils are 
found in the various terranes now referred to the Algonkian, it will be impos- 
sible to make any correlations that will be more than tentative suggestions. 
Sapper,* in 1894, describes and maps considerable areas of Azoic formations 
in Guatemala. The lowest formations are gneiss and the higher formations 
are mica-schists and phyllites, associated with which are crystalline limestones, 
actinolite-schistt, and quartzites. Closely associated with these schistose 
rocks are ancient eruptive rocks, including granite, diabase, etc. Whether 
these Azoic formations are pre-Palaozoic or not cannot as yet be asserted. 
t Algonkian Rocks of the Grand Canyon of the Colorado, by C. D Watcort, 
Jour. oF GEOL., Vol III., April-May 1895, pp. 312-330, and 14th Ann Rep. U.S. 
G. S. (for 1892-3), Part II., pp. 487-524. 
?Grundziige der physikalischen Geographie von Guatemala, by CARL SAPPER, J. 
Perthes’ Geog. Anst., Erganzungsheft, Nr. 113, 1894, pp. 59, with 4 maps. 
