| 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.
|
