21. The original surface was red shale , which needed repeated rolling. 22. The Chugwater consists mainly of siltstone and shales with interspersed sandstones. 23. Limestones, shales , and sandstones indicate a predominantly marine environment. 24. The creek flows through rock formations made of sandstone and shale . 25. Shale shakers are the primary solids separation tool on a rig.26. Rock formations consisting of sandstone and shale occur in the watershed. 27. The creek flows through rock formations made of shale and sandstone. 28. It mainly flows through rock formations consisting of sandstone and shale . 29. Many of these black shales are now rich in petroleum sources. 30. Sometimes non-shales also have elevated levels of gamma radiation.
