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GEOLOGIC GUIDEBOOK ALONG HIGHWAY 49 



[Bull. 141 



group of plugs, of which there are three besides the Golden Gate plug 

 considerably farther west, are made up of a rock described as hornblende 

 andesite. These supposedly are the vents from which the Mehrten vol- 

 canics were derived. 



MOKELUMNE HILL TO PLYMOUTH MAP 5 



Between Mokelumne Hill and the canyon of the Mokelumne River 

 the terrain is hilly. The Tertiary gravel and volcanic series has largely 

 been stripped off and the tributaries of the Mokelumne have badly dis- 

 sected the old Eocene surface. West from town, Jackson Butte, a lofty 

 volcanic plug, stands out above the other hills. Far beyond and to the 

 northwest the metal water tank of the Argonaut mine can be seen on the 

 ridge top. The bedrock along the highway is diorite and related plutonics 

 until well beyond the Mokelumne River. A few gravel remnants outcrop 

 near the road within sight of Mokelumne Hill. 



One and four-tenths miles north of the Mokelumne River bridge the 

 road passes through a thick series of tuffaceous gravels which are part 

 of the placer ground of the Butte City mining district. The site of Butte 

 City can be located by the ruins of the Butte Store and State Division of 

 Highways Historical Marker 39. Beyond Butte City 1.3 miles, an oiled 

 road turns to the west which connects with the old placer camp of Mid- 

 dle Bar on the Mokelumne River about four miles from Butte City. The 

 bridge which now crosses the Mokelumne is about at the old site. The 

 river bottom is now flooded most of the year by the waters backed up 

 behind Pardee Dam. Little Bar is commemorated by State Division of 

 Highways Historical Marker 36. A mile farther north, a road from 

 Clinton leads off to the east. The Clinton mining district is on the East 

 Belt close to the granodiorite contact. The Clinton Consolidated and 

 Clinton Bar are the best known lode mines of the district. Clinton was 

 a placer district before the lode mines were developed. State Division of 

 Highways Historical Marker 37 marks the turnoff to Clinton. 



The dumps and mine buildings of the Zeila mine are located close 

 to Highway 49, six-tenths of a mile south of Jackson. The Zeila was first 

 opened in the 1860 's, was closed down during the latter half of the 70 's 

 and was a heavy producer from 1880 to 1914. The mine has an inclined 

 shaft which is 1700 feet deep along an incline of 65 average dip. The 

 ore occurs in quartz stringers in a gouge composed of decomposed rocks 

 of several types. The veins lie on the contact of Calaveras slate and 

 schist and greenstones of uncertain age. One drift is over 3000 feet long. 

 Total production of the Zeila has been more than $5,000,000. 



Northward from the Zeila mine to the vicinity of Plymouth, a dis- 

 tance of about 12 miles, the Mother Lode has produced gold far in excess 

 of $160,000,000. This is by far the richest yield recorded along the Mother 

 Lode for any sector of equal length, and is exceeded in California, in 

 total gold produced, only by the Grass Valley district of Nevada County. 



The geology of this highly productive strip is complicated both in struc- 

 ture and in lithologic similarities, and there are many diverse interpre- 

 tations of the geology by those currently at work there. Most of the pro- 

 ductive mines are on a branch of the Mother Lode thrust fault system 

 known locally as the Gold Thrust. The main Mother Lode fault which lies 

 about a mile to the east of the Gold Thrust is nonproductive along this 

 sector. The strike of these two faults is roughly N. 30 W. and parallels 

 the regional trend of the structure for the most part. Other faults of 

 similar type and trend occur several miles to the west of Jackson and 

 are undoubtedly other branches of the Mother Lode system. The Jurassic 

 sediments and metavolcaiiics in this area are badly deformed into a series 

 of tight, overturned, isoclinal folds which have been further complicated 

 by the several thrust faults mentioned above. 



Jackson, the county seat of Amador County, is a vigorous, modern 

 town combining the old with the new. Many of its old buildings have had 

 their faces lifted so that one would hardly recognize their true vintage. 

 Jackson bears the name of Colonel Alden Jackson who has also been 

 honored by having the Tuolumne County town of Jacksonville named 

 for him. The town dates from at least 1849 and probably before. Botilleas, 

 the original name for the site, indicates that, like many other gold camps, 

 Spanish Californians were the original settlers. Jackson is very proud of 

 its one-time Congressman, benefactor, and native son, Anthony Cami- 

 netti, who did a great deal for Jackson and for Amador County in gen- 

 eral. A monument to his memory has been erected beside Highway 49 

 immediately north of the business district. 



Jackson Gate is a small town located 1.5 miles north of Jackson and 

 reached via paved road from either Jackson or Martell. Although small, 

 Jackson Gate is picturesque and is the possessor of a group of very 

 interesting relics of the past mining ventures. To the north and east of 

 town are several huge wheels which were built in 1902 to raise tailings, 

 or mill waste, from the ground level of the Kennedy mine, situated a half 

 mile to the west, to the summit of a ridge beyond which lay the tailings 

 disposal dump. Although partly dismantled, the wheels were once 

 equipped with a circle of 176 buckets, a belt drive, and an electric motor 

 each. They were 68 feet in diameter and raised the tailings a vertical 

 distance of 48 feet each. The tailings elevators connected gravity flumes 

 in which the tailings flowed from mill to dump. Sheet metal buildings 

 once housed each wheel but these have been removed. 



Two of the greatest mines on the Mother Lode are located slightly 

 more than a mile northwest of Jackson. These were exceedingly large 

 operations both above and below ground and are famous landmarks 

 along Highway 49. The Kennedy, with its lofty headframe and huge 

 sheet-iron-enclosed mill, lies a short distance to the east of Highway 49. 

 The original Kennedy claim was located in 1856 and has since be.en 

 consolidated with several others. It was a minor working until 1871 



