Geology of Ft. Apache Regioji, Ariz. — Reagan. 2.yj 
river, where not covered with lava or Quaternary de- 
posits. These schists, wherever exposed, were seen to 
grade into gneiss and syenyte and these in turn to 
grade into granite, there being no unconformability between the 
upper and lower series (the schists and the granite) so far as 
the writer knows. The Huronian and Laurentian systems may 
be represented in the Archaean here; but at present, evidence 
is wanting to warrant such identification. 
The Archaean rocks seem to culminate in an east and west 
ridge beneath the clastic rocks in about the latitude of Ellison. 
This ridge is not the result of uplift because the elastics all dip 
to the north irrespective of the ridge. Again the ridge may 
have existed prior to the deposition of the sediments, because at 
its crest the Algonkian series is wanting. 
The Algonkian. — The Algonkian rocks are exposed along 
the edge of the southwest escarpments of the Plateau region, in 
the Salt River canyon from the Pinal mountains on the west to 
the confluence of Corrixo creek with Salt river on the east, and 
in the Canyon Creek valley from Salt river north to Chid- 
dessky. It is the country rock of nearly all the mesa between 
Cherry creek and Canyon creek from the Ellison post office 
south to Salt river, as well as of the mesa between Canyon and 
Oak creeks. It is also exposed in the middle Cherry Creek 
valley and along the east wall of Sierra Ancha. These rocks, 
in the main, are composed of massive lava flows of the dioryte 
and diabase types interstratified with sandstones, mottled, cor- 
alloid limestones, and many-colored shales. This series is un- 
conformable with the underlying Archaean, and with the over- 
lying Tonto. It begins with a conglomerate, and the Tonto 
which immediately overlies it is also conglomeratic. 
The lost record represented by the unconformity of this ser- 
ies with the Archaean must be very great, at least as great as 
that represented by the unconformity between the Algonkian 
and the Archaean in the Grand Canyon series. But the lost 
record between the Algonkian and Tonto was much greater 
here than there — indeed so great that the Chuar terrane and 
the greater part of the Ukar terrane are wanting. These un- 
conformitiesv, besides indicating a lost record, are evidence that 
this region was a land area both at the close o fthe Archaean 
