Friday, June 17, 2011

Where did the Wingate go?

If you have read this blog for any amount of time, you have already gathered that my favorite formation on the Colorado Plateau is the Wingate sandstone. In fact, the cover photo of the blog is of the Wingate sandstone along the Green River. It is a late Triassic- Jurassic aeolian sandstone. The grains are very uniformed in size making fantastic conchoidal fractures when blocks fall from the cliff face. Making a very nice cap rock on top of the Wingate is the Kayenta formation. The Kayenta, an early Jurassic siltstone-sandstone showing evidence of mid energy stream action is cemented very well and acts as an excellent cap rock. The top most component of this group (the Glen Canyon Group) is the Navajo Sandstone. This sandstone is another Jurassic aeolian sandstone that hints at being one of the largest sand islands ever seen on planet earth.

But...back to the missing Wingate.

Most of my play area is in Southeast Utah along the Colorado and Green Rivers. This past month we have spent some serious time in South central Utah in the Paria drainage. Here we see the familiar Glen Canyon Group wit the navajo sandstone along the horizon, the Kayenta formation directly below but instead of another aeolian sandstone there the Moenave Formation with reddish siltstone and pinkish sandstone showing clear evidence of water deposition. What a difference from the windblown Wingate.

The story in the rocks suggests that perhaps, in the early Jurassic we would have been in a desert resort area with ponds and streams with a large desert just to the east. A paleo-Palm Springs?

Canyon cliffs of Navajo sandstone with the Kayenta formation making the canyon bottom
Canyon walls of Wingate sandstone
And 100 miles to the west... the high white cliffs of Navajo sandstone, the reddish ledges of the Kayenta formation and the reddish-pink slope forming Moenave formation near the bottom.

1 comment:

vebiltdervan said...

I'm a geologist & used to put groups together to do geologic-themed Colorado River trips through the Grand Canyon. I've noticed that, as I drive north from Flagstaff to Lees Ferry on US Hwy 89, the Wingate is a prominent cliff-forming unit in the Echo Cliffs to the east, easily visible from the car north of the Tuba City turnoff. However, further north that prominent Wingate cliff rapidly disappears over a short distance, north of The Gap, before one gets to the Hwy 89A turnoff to Marble Canyon & Lees Ferry. And hence I wasn't too surprised when I hiked the Paria, as you did, that the Wingate is missing from the 'Vermilion Cliff' stratigraphic section there.

Bill Wade