Questions and phone orders: 10 AM - 10 PM Pacific (760) 920-6465

shale - hard tan shale from the Green River Formation, an Eocene lacustrine petroleum source rock - teaching hand specimen

$ 7.50

The Green River Formation was deposited in a series of lake basins formed as a result of mountain building during the Laramide orogeny, with deposition largely occurring during the Eocene. The lakes alternated from fresh water to saline-alkaline phases  and covered a large area in northeastern Utah, southwestern Wyoming and northwestern Colorado.

The lithology of the Green River Formation varies widely, in places 33% organic carbon by weight. Typical of the organic-rich shale, the “mahogany layer” of the Parachute Member is technically a kerogen saturated lime mud, though it is referred to as oil shale, and was experimentally mined, primarily in the 1970s, in Parachute Canyon, Colorado, with an eye on its petroleum potential. Costs were high and the potential was unrealized, though Unocal produced five million barrels of oil in their Parachute Canyon plant in the 1950s ‘60s and ‘70s.

Near Bonanza, Utah and at Douglas Pass, Colorado, the shale contains prolific fossil plant and insect sites, recording Rocky Mountain vegetation during the early middle Eocene, and providing information about the nature of the ecosystems that surrounded the Eocene lake systems. This shale is durable because of its laminated hydrocarbon-rich nature, allowing preservation of entire branches instead of the single leaves typical of most other fossil leaf localities. 

This shale was collected near the FAA radar dome at Douglas Pass, in the divide between the Piceance Creek and Uinta basins.  It has a leaner organic content than the  hydrogen-enriched shale of the Piceance Creek basin to the east.




Making multiple purchases? Click on the "combine shipping" button in the shopping cart. We'll send an invoice with combined shipping. A link in that invoice will bring you back to checkout, no hassle.

Select a specimen: When more than one specimen is shown, you can select a particular specimen by telling us what is in the photo with it, a blue or black and silver pen, a black mechanical pencil or one of those plus some number of coins, or you can let us make the selection.

Shipping: By Priority Mail or USPS Ground Advantage, whichever is cheaper, unless we find a better rate. Click > here < for shipping rates. Use back button to return to this page.