Moreno shale

Since selenium substimtes for sulfur in the stmcture of sulfide minerals, drainage from mineralized and mined areas may have high dissolved selenium concentrations. Acid seeps derived from oxidation of sulfide minerals draining the Moreno Shale in the Coast Ranges, USA, have selenium concentrations up to 420pgL with concentrations of aluminum, manganese, zinc, and nickel in the mg L range (Presser, 1994). 

The primary source of the selenium is believed to have been pyrite in shales, particularly the Upper Cretaceous-Paleocene Moreno Shale and the Eocene-Oligocene Kreyenhagen Shale. Concentrations of selenium in these formations range up to 45 mg kg median concentrations being 6.5 mg kg and 8.7 mg kg respectively (Presser, 1994). The concentration of selenium in the surface sediments (0-0.3 m depth) of the old playas is in the range l-20mgkg reflecting the historical accumulation of selenium from the selenium-rich drain water. Deeper sediments... 

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