The Western Slope shale in Colorado is not one single layer with one fixed depth; in practice, the depth depends on which shale formation you mean and where you are on the Western Slope. In western Colorado, major shale-bearing units include the Mancos Shale and the Piceance Basin’s shale-rich formations , and their depths can range from shallow near outcrops to thousands of feet underground.

What “depth” usually means

If you’re asking about the shale targeted for oil and gas, the relevant formations are usually buried far below the surface , often around thousands of feet deep in productive basin areas. The broader Denver Basin reference in the search results shows Colorado basin geology can extend to more than 13,000 feet deep, though that is for the basin as a whole, not a specific shale layer on the Western Slope.

Western Slope examples

  • Mancos Shale : a major Cretaceous marine shale on the Western Slope, especially in the Four Corners and nearby basins.
  • Piceance Basin shale intervals : deep enough to support substantial gas development, with basin-scale geology reaching very large depths.
  • Surface exposures : in some places, shale is visible at or near the surface, so depth varies a lot by location.

Practical answer

A safe plain-English answer is: the Western Slope shale formations are generally buried from near-surface outcrops to many thousands of feet deep, depending on location and the specific formation. If you want the depth for a specific county, town, or formation name like Mancos Shale or Pierre Shale , I can narrow it down precisely.