Add to top Helmer mine section. (going up strat) 1.2 Pizty argill, siltstone. 3.6 Shale, grey plastic finely silty 1.7 IB, shale as above and platery argill, siltstone. 0.1 Bentonite ---- Shale gray, few silty beds - this is Gonzeros Notes on Helmer section: Total absence of any Dakota clay is noteworthy - SS. is much thicker than would appear at surface because it is frizble, points to fallacy of assuming Dakota clay present. Main source of clay is bed above main bed. Its character in the area, from Helmer gap south, is distinctive and not like [illegible] clays to north. 6.