| Clue | Source | Date |
|---|---|---|
| See man, seaman, their great source of oil you'll plunder no more... (6) | ||
| Oil-bearing rocks | LA Times Daily | 04 Apr 2022 |
| Oil-bearing rocks | The Washington Post | 04 Apr 2022 |
| Fissile rocks | LA Times Daily | 08 Oct 2020 |
| Fissile rocks | The Washington Post | 08 Oct 2020 |
| Sedimentary rocks | Premier Sunday | 30 Jun 2019 |
| Sources of oil | New York Times | 07 Mar 2018 |
| Sources of oil | ||
| Some sedimentary rocks | Universal | 07 Feb 2017 |
| Oil-bearing rocks | LA Times Daily | 14 Jun 2016 |
| Oil-bearing rocks | ||
| Pulitzer-winning TV critic Tom | Wall Street Journal | 12 Nov 2015 |
| Pulitzer-winning TV critic Tom | ||
| Some are bituminous | ||
| Fossil rocks | ||
| Fuel-yielding rocks | ||
| Fuel-yielding rocks | ||
| Rocks formed from clay | ||
| TV critic Tom | ||
| Synthetic fuel sources | ||
| Fuel-yielding rocks | ||
| Fossil-yielding rocks | ||
| Layered minerals | ||
| Pulitzer-winning journalist Tom | ||
| Fossil-yielding rocks | ||
| Laminous rocks | ||
| Terrigenous rocks | ||
| Oil-producing rocks | ||
| Fissile rocks | ||
| Layered rocks | ||
| Fissile rocks. | ||
| Fine-grained rocks. | ||
| Layers of rock. |