"One core feet in one 1200 foot long trough arkysdrite, or this thicker than not more than a foot of black shale. The greater part of the arkydrite is very regular laminated. The arkydrite layers are usually about 1/2 mm. thick, and could count something like 10 to 12 to the inch. Hidden interprets this lamination as due to seasonal oscillations, and believe that it took about 300,000 years to lay down the arkydrite. According to my calcu- lations I get 144,000 years. 1200' 1/2'' 24000 1200 1240,000 tank print years 144,000 years by them. Hacks tanks. This maybe from carbon dust and organic material. Hidden thinks he has in his headlands and others get an abundance of Radiolarians but during time that I looked is more like such. Below the arkydrite is much Hack