Henry Mountain Structure

8/4/2019 Henry Mountain Structure

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Henry Mountain Structure, Hanksville, Utah

Tim McElvain

The Henry Mountains are conventionally described as Mid-Tertiary,

shallow emplacement, laccolithic structures and are more particularly

described in the publication:

Geology of the Tertiary Intrusive Centers of the La Sal

Mountains, UtahInfluence of Preexisting Structural Features on

Emplacement and Morphology

By Michael L. Rosshttp://pubs.usgs.gov/bul/b2158/B2158-9.pdf

The Henry Mountains are located approximately 80 miles East

Southeast of Moab, Utah.
http://pubs.usgs.gov/bul/b2158/B2158-9.pdfhttp://pubs.usgs.gov/bul/b2158/B2158-9.pdf


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View looking southwest at the southern half of the Henry Mountains, Mt.

Pennell to the left and the North and South Summit Ridge consisting of

Kimble, Turner, and Mt. Ellen Peak to the right.


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View looking west at the North and South Summit Ridge of the Henry

Mountains consisting of Mt. Kimble, Mt. Turner, and Mt. Ellen.


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Map of the Henry Mountains with my waypoints plotted on it and marking

the area where I found the Shatter Cones(?) illustrated below.

PLANAR MICROSTRUCTURES

The following photomicrographs of quartz grains with planar

microstructures, (PM's) were made from samples of sandstone (possibly

Dakota sandstone) collected at the southern end of the Henry Mountains to

the east of Mt. Hillers, and between Mt. Pennell and Mt. Hillers. The scale

of the PM's fit the scale ofplanar deformation structures, (PDF's) which I

believe they are but they have not been verified by the experts in the field ofimpact structure geology. If they prove to be PDF's they would be diagnostic

of an impact structure.


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The above photomicrograph is of a quartz grain with two sets of PM's

illuminated with cross polarized light.


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The above photomicrograph is of a highly shocked quartz grain with three

sets of PM's illuminated with cross polarized light.


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The above photomicrograph is of a highly shocked and plastically deformed

quartz grain with three possibly five sets of PM's illuminated with cross

polarized light.


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The above photomicrograph is of a cataclastic, micro-clastic dike in the

same sandstone as the above photomicrographs of planar microstructures

illuminated with cross polarized light.


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The above photomicrograph is of a quartz grain collected from a sandstone

(possibly Dakota sandstone) at Waypoint 02075 located to the east of Mt.

Hillers.

SHATTER CONES

The following photos of possible shatter cones were taken in the area

indicated on the above map. The proposed shatter cones are not classic

shatter cones, nor are they slickensides. The horsetail striations are on a

curved surface but not on a conical surface. Some of the shatter cones at theSanta Fe Impact Structure are similar; however, at Santa Fe the surfaces

have more curvature than at this location (Waypoint 08020) in the Henry

Mountains.


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The above photograph of horsetail striations on a curved and grooved

surface is very interesting.


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The above photo is a close-up of the same shatter cone cast (08016) with

rather faint horsetail striations.

The following photomicrographs are of quartz grains with planar

microstructures were made of grains of quartz taken from the orthoquartzite

making up shatter cone sample 08016 above.


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The above photomicrograph is of a quartz grain that has one set of planar

microstructures (PM's) that are somewhat difficult to see in the northwest

quadrant of the photomicrograph and one set of planar fractures (PF's).

Summary

The above evidence indicates to me that the Henry Mountains, Hanksville, Utah are thecentral uplift of a large impact crater.

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Henry Mountain Structure