84 WARREN DUPRE SMITH AND EARL L. PACKARD 



1. The coastal lakes — type, Tsiltcoos Lake. 



2. The alkali lakes of the southeastern desert region — type, 

 Harney Lake. 



3. Crater lakes — type, Crater Lake. 



4. Morainal lakes — type, Wallowa Lake. 



5. Cirque lakes — type, Aneroid Lake. 



6. Fault block depression lakes — type, Warner Lake. 



7. Lava flow lakes — many in high Cascades. 



STRATIGRAPHY 



PRE-CAMBRIAN 



Archean. — A biotite gneiss, imbedded in the granodiorite 

 occurring along the headwaters of the north fork of John Day 

 River is thought to be the oldest known rock of Oregon. This 

 metamorphic rock outcrops on the north slope of Bald Mountain, 

 covering an area of less than fifteen square miles. There is no 

 reason given by Lindgren' why these rocks are considered as being 

 pre- Cambrian. It is true that they are similar lithologically to 

 gneisses in Calaveras County, California, and those near Shoup and 

 Elk City, Idaho. Since metamorphics are products of dynamic 

 conditions irrespective of time, there is no valid reason why gneisses 

 and schists may not be found in later ages. 



Algonkian. — ^Metamorphic rocks of supposed pre- Cambrian 

 age also occur at or near the California-Oregon boundary. Schists 

 are found near the headwaters of Wagner Creek west of Ashland, 

 at Starling Peak still farther to the west, and thence westward along 

 the boundary line to Takilma, interrupted, however, by smaller 

 masses of Paleozoic metamorphics. These areas, excepting the first 

 mentioned, extend into California in a southeasterly direction for a 

 distance of many miles. These rocks are variously described by 

 Diller,^ WinchelV and others as amphibolite, hornblendite, 

 hornblende-mica, talc, and mica-quartz schists. Since they are 

 either continuous with, or lithologically similar to, the beds across 



' U.S. Geol. Surv., 22d Ann. Kept., Part II, p. 594. 



^ J. S. Diller, U.S. Geol. Surv., Bull. 546, p. 14. 



3 A. N. Winchell, Oregon Bureau of Mines and Geol., Vol. I, No. 5, p. 37. 



