diller.] FLUVIOESTUARINE DEPOSITS. 41 
seaward summits appear very recent and may be Pleistocene, but to fix these 
accurately and conclusively more lengthened and detailed study will be required 
than any rapid reconnaissance can afford. 
NEAR ROUND VALLEY. 
A most important deposit of Neocene beds occurs on Middle Fork 
at the month of Salt Creek, 8 miles southwest of Covelo, Mendocino 
County. These beds have been described by Mr. Goodyear 1 and 
others, 2 who give a detailed section of the deposit on account of the 
coal bed it contains. The coal is about 14 feet thick, strike N. 25° 
W., dip 25° NE., and lies between fragile shales having a total thick- 
ness of about 100 feet. Shells are reported, but their determination 
is not given. 
The same formation extends up Salt Creek for a number of miles. 
Three miles west of Eden Valley, near the head of Salt Creek, an 
oyster bed occurs with 20 feet of soft shale having essentially the same 
strike and dip as that a few miles northwest. It rests directly upon 
serpentine at an elevation of over 3,700 feet. Fossils from this local- 
ity were referred to Dr. Dall, who reports " fragments of a very large 
oyster and small barnacles of Miocene type, but specifically indeter- 
minable owing to defective state. This locality is especially interest- 
ing as representing about the most eastern part at which Miocene 
marine beds have been detected in northern California." On the map 
(PL I) the approximate coast line of the Miocene is indicated, and it 
may be seen that practically the whole of the northern end of the 
Coast Range was then below sea level. 
FliTJVIO-ESTUARINE DEPOSITS OF TRINITY DRAINAGE. 
AT HYAMPOM. 
In addition to the purely marine Neocene deposits, all of which lie 
on the southwest side of the shore line indicated on the map, there 
are other deposits of brackish- or fresh-water origin whose relation to 
those occurring nearer the coast is not yet fully known. They occur 
at Ilyampom and Hay Fork, along Hay Fork, which drains into 
the South Fork of the Trinity, and at Big Bar, Weaverville Basin, 
Redding Creek Basin, and near Lowdens, all of which are drained by 
Trinity River. The general distribution of these deposits was out- 
lined some years ago," but fossils lately found have given greater defi- 
niteness to our knowledge of them. 
Ilyampom is at the junction of Kay Fork and the South Fork of 
Trinity River, at an elevation of about 1,400 feet. In September, 1889, 
the writer passed that way and observed coal-bearing rocks at one 
place having a thickness of about 40 feet, with a strike N. 10° to 25° 
1 Coal Mines of the Pacific Coast, p. 74. 
2 State Mining Bureau of California, Twelfth Report of the State Mineralogist, p. 57. 
fourteenth Ann. Rept. U. S. Geol. Survey. Pt, II, 1894, PI. XLV, p. 414. 
