Red Bentonite Clay HillJurassic Badlands

Red Bentonite Clay Hill Jurassic Badlands

full print size of 28.6x37.6 inches @304.8ppi, above displayed at 1/178
Copyright © David Senesac 2005   view detailed crop

geranium Capitol Reef National Park, Wayne County, Utah
late afternoon Saturday May 30, 2005, slide 05-L-83
Wisner 4x5 Expedition, 90mm Caltar, Gitzo G1325 Mk2
Tango Drum scanned Fuji Provia 100F 4x5 film to 300mb RGB file
Adobe Photoshop 6.0 processed for accurate image fidelity
Lightjet5000 printed on Fuji Crystal Archive paper
signature mid lower left          

In 1997 I had taken a wonderful 35mm image near this location and was determined during our May 2005 trip to take another with the 4x5. The area is in the San Rafael Desert where there is a considerable exposure of Jurassic sediments. The landscape here is as unworldly as one will find on our planet Earth. We were having a difficult time photographing this zone because of too many afternoon clouds shadowing the landscape. Finally on this Saturday we had some sun and hurried about taking frames we had previously found. Unfortunately it was also very windy. Thus we were spending quite a lot of time after setting up shots waiting for momentary lulls. I thought this frame captured the smooth voluptuous essence of this earthy scene. I centered the sinuous S crease a bit below center frame then pointed it to intersect the background geometry. Oh and yes if one walks on this surface, one leaves a footprint several inches deep. So this is absolutely pristine with no one having been here for at least a few years.

These smooth contoured hills are made of soft light reddish purple and tan lacustrine mudstone and siltstone bentonitic deposits. Geologists have designated this the Salt Wash Sandstone Member of the Morrison Formation. Lacustrine refers to lake deposits, as this foreground was part of a vast warm shallow inland sea during the late Jurassic about 150 million years ago. Bentonite refers to silting deposits from fine volcanic ash sources. The soft easily eroded clay surface expands when rain falls on it, and then contracts when it dries under the hot arid high desert sun creating the odd crinkly surface.

When wet this same clay surface becomes a quite slippery and dangerous vehicle road surface on dirt roads in the area.

At the left skyline above these banded layers is a second formation, a light gray tan ridge of younger overlying Brushy Basin Shale Member of the Morrison Formation that is famous in Utah for containing petrified wood and dinosaur fossils. The slight greenish yellow tints are strange bottle plants, eriogonum inflatum, that were blooming during our visit. At the right frame edge above a light section of the Brushy Basin on a ridge further back is a third formation. This gray layer is lower Cretaceous Period Mancos Shale Tununk Shale Member rock. Shale, a sedimentary rock, differs from siltstone or mudstone by originating from aquatic sedimentations of finest sized particles. Above the Tunuck Shale on the right skyline is a fourth formation, a ridge of slightly more yellow Ferron Sandstone Member of Mancos Shale.

In the background a fifth formation forming the mesa sides consists of easily eroded Mancos Shale Blue Gate Shale Member. These are upper Cretaceous marine deposits of pale yellow sandstone interbedded with gray carbonaceous shale. The top of the mesa is the sixth formation, a thin hard mesa-capping layer of Mancos Shale Emery Sandstone, the youngest strata in this image. Some of the most impressive badlands in the World.

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   David Senesac

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