The yellowish-gray Shinarump is a very distinct member found intermittently at the base of the Chinle Formation. Its discontinuous nature hints at the way it was deposited. Shinarump sediments, laid down in the channels of rivers that meandered across a coastal plain 200 million years ago, are composed of sands and gravels like those in many shallow river beds today. Because rivers meander instead of blanketing an area, the Shinaump is visible only sporadically.
Shinarump also contains uranium ore. The old mine tunnels at the mouth of Grand Wash penetrate the Shinarump.