442 DILLER AND STANTON — THE SHASTA-CHICO SERIES. 



SECTION ON COLD FORK OF COTTONWOOD CREEK. 



The Cold fork of Cottonwood creek is about 15 miles north of Elder 

 creek. The section it affords was not measured, but was examined sev- 

 eral times with some care. At this point the Aucella beds are not so 

 thick as on Elder creek, and j^et they must be in the neighborhood of 

 10,000 feet thick, for they are exposed with a steep dip over a belt of 

 country Sj miles in width across the strike. The basal beds are shales 

 with local conglomerates and rest directly with a conspicuous uncon- 

 formity upon the metamorphic rocks. In the adjacent hills the meta- 

 morphic rocks are found, and among them are a number of limestones. 

 One of these has afforded an imperfect ChcXtetes, which Mr Walcott has 

 referred to the Carboniferous. The basal conglomerates of the Knox- 

 ville series contain pebbles of these limestones. 



Aucella was discovered in this region by Mr H. W. Fairbanks. It 

 occurs rather abundantly in the upper portion of the Knoxville beds. 

 Five-eighths of a mile up a small ravine which enters Cold fork just 

 above Mr Stephenson's house Aucella was found in the same bed with 

 numerous other fossils noted on page 449, so that there can be no doubt 

 whatever concerning their association. 



The overlying beds in this section differ somewhat from those on 

 Elder creek in containing a fetid limestone about 30 feet in thickness. 

 It contains Ammonites ( Olcostephanus) deansil, Whiteaves ; Atresius liratus, 

 Gabb (?) ; Modlola major, Gabb, and Ctjprina (?), n. sp., and is probably 

 about the same horizon as one of the limestones reported by Whitney 

 and others in Colusa and adjoining counties to the southward, where 

 they are said to be closely related with the Aucella beds.* 



SECTION ON NORTH FORK OF COTTONWOOD CREEK. 



This section has been measured and is given in the accompanying 

 table. It is well exposed along the north fork of Cottonwood creek and 

 its branches above Gas Point. In the vicinity of Ono the Horsetown 

 beds rest with marked unconformity directly on the metamorphic rocks. 

 At the base there is a heavy conglomerate which is derived directly from 

 the metamorphic rocks near by. Aucella has not been found in this 

 section, though the fossils of its basal portion are identical with those 

 that occur in beds adjoining the Aucella beds in the Bald hills near Elder 

 creek. The Horsetown beds in this section have a thickness of 5,200 

 feet, and consist chiefly of shales and thin sandstones. They have 

 afforded a large number of fossils, many of which have already been 

 described by the paleontologists of the Geological Survey of California. 



* See references by Gabb in Paleontology of California, vol. ii, pp. 192, 195. 204, 



