Jurassic Wingate Sandstone Stratigraphy

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The Wingate Sandstone is a widespread eolian sandstone across much of the Colorado Plateau. It forms massive cliffs along the Colorado NW of Moab, UT, the cliff-forming sandstone along Hwy 211 leading toward the Needles area of Canyonlands National Park (Indian Creek), and Comb Ridge.

This unit can be a little confusing because I'd assumed that the type locality for the unit was Fort Wingate in NM. However, the USGS geologic maps had multiple members of the Entrada and Morrison in the region. I couldn't make hide nor hair of it until I read Green (1974). He did a careful study (accepted by later researchers) and the unit along the Wingate Cliffs that *used* to the be the type locality for the Wingate Ss is not at all! It's now the newly defined lower unit, the Iyanbito Member of the Entrada Sandstone. The two overlying member here are the Middle Siltstone Member and the topmost Upper Sandstone Member. This leaves the problematic situation that the Wingate Sandstone no longer has a type locality!

Another puzzling thing for me was why the Wingate was so prominent near Moab, Comb Ridge, but isn't apprarent at the Echo Cliffs or Vermillion Cliffs. Now I see it has had a facies transition to the Moenave Formation to the south and west. Here is a figure adapted from Kirtland and Milner that explains a lot.

 

This shot comes from Indian Creek along Hwy 211 on the way to the Needles of Canyonlands. All of this is Triassic in age, though the Navajo Sandstone is Triassic-Jurassic. You can barely see a tiny bit of the Navajo at the top. The contacts look wonky because of the 3D nature of the outcrop, plus the cover of the float. I took the nomenclature of the Chinle from the USGS topo map. They map a lower Moss Back Member and an upper member. I am guessing that the minor ledge forming unit is the Moss Back. The upper part of the Chinle doesn't show its normal bright colors in this shot because of the loose materials washing down the slope. No Moenavi here! Click HERE for a full-sized image.

 

Until I get a shot of this of my own, here's a page that show the stratigraphy at Comb Ridge, including the prominent Wingate SS:

https://geology.utah.gov/map-pub/survey-notes/geosights/comb-ridge/

 

 

Green, Morris W., 1974, The lyanbito Member (A New Stratigraphic Unit) of the Jurassic Entrada Sandstone, Gallup-Grants Area, New Mexico, US Geological Survey Bulletin 1395-D, 12 p.

Kirtland, James I. and Milner, Andrew, 2006, The Moenave Formation at the St. George Dinosaur Discovery Site at Johnson Farm, St. George, southwestern Utah in: New Mexico Museum of Natural History and Science, Bulletin 37.