Lower Ferron Sandstone and Juana Lopez Members of the Mancos Shale around the north side of the San Rafael Swell

In an attempt to show that the Juana Lopez Member of the Mancos Shale really does expose itself on the west side of the San Rafael Swell, I introduce some photos to help.

Lower Ferron east of Huntington (visible upper right).

Lower Ferron east of Huntington, these beds contain Prionocyclus hyatti near Mounds.  They also form a small cliff under the Ferron Sandstone south of here from Ferron south to Last Chance Creek.

Juana Lopez Member east of Huntington (visible upper left)  Prionocyclus macombi concretions in middle of cliff  (right) and P. wyomingensis concretions at top of cuesta across wash.

Juana Lopez Member east of Huntington.  The same thin platy siltstone beds that appear on the east side of the swell appear here with the same platy rubble littering the slopes.  The concretion beds are also the same.

Two beds of the Lower Ferron Sandstone with large round concretions just north of Mounds.  Lower bed contains the ammonite Prionocyclus hyatti along with many other mollusks.

Around the north side the Juana Lopez is still there above the Lower Ferron.

Juana Lopez Member just west of Cat Canyon where Highway 6 and 191 cut through the Farnham Dome just east of Wellington.  Prionocyclus wyomingensis beds at top of cuesta in middle distance (Light cliff), P. macombi concretions in middle of slope.  Farnham Unit of Lower Ferron Sandstone in foreground.  Some minor faults also in foreground, one duplicating the orange bed in center.

The same thin siltstone beds, the same platy rubble.

Lower Ferron Sandstone just below dark Juana Lopez Member, 1 mile southwest of Grassy Siding.  Coon Spring Sandstone Bed at base.  Brown concretion to left center is what's left of the P. hyatti beds at Mounds.

On the east side of the Swell, the beds above the Lower Ferron have been refered to the Juana Lopez.  The only real difference I can see is a couple (2) of thin (2cm max) calcarenite beds.  South and east of Green River the Juana Lopez has more and thicker calcarenite beds.

Juana Lopez Member just west of Grassy Siding, Mt. Elliot in right distance.  Prionocyclus macombi concretions form edge of middle cuesta, P. wyomingensis concretions form orange lip of upper cuesta.

 Here on the east side are the same thin bedded siltstone beds, the same platy rubble, and the same concretion beds with the same fossils.  The siltstone beds on the west side maybe get a bit thicker, up to 3 or 4 cm, even more reason not to refer them to the Blue Gate Shale.

References:

Dane, C. H., Cobban, W. A., and Kauffman, E. G., 1966, Stratigraphy and Regional Relationships of a Reference Section for the Juana Lopez Member, Mancos Shale, in the San Juan Basin, New Mexico, U.S.G.S. Bulletin 1224-H

Edwards, C., D. Hodgson, S. Flint, and J. Howell, 2005, Contrasting styles of shelf sediment transport and deposit in a ramp margin setting related to sea-level change and basin floor topography, Turonian (Cretaceous) Western Interior of central Utah, USA: Sedimentary Geology, v. 179

Molenaar, C. M., and Cobban, W. A., 1991, Middle Cretaceous Stratigraphy on the South and East Sides of the Uinta Basin, Northeastern Utah and Northwestern Colorado,   U.S.G.S. Bulletin 1787-P

Ugly Map Colors

Too bad modern geology is taking a step backward with their geologic mapping colors.  I have yet to see an official standard calling out the new colors. You used to get a choice at stratigraphy.org, but no more.  Are they using a traditional system for the sake of tradition under the guise of priority.  This is almost as bad as illustrating ammonoids upside down of their assumed life position (again, mainly tradition).  It is like moving away from Metric Units back to Imperial feet and inches.  Why random colors?  The divisions are called Systems or in the case of rock units, Series.  Why wouldn't the colors look better in order or series?

CGMW		USGS
	Quarternary
	Neogene
	Paleogene
	Cretaceous
	Jurassic
	Triassic
	Permian
	Pennsylvanian
	Mississippian
	Devonian
	Silurian
	Ordovician
	Cambrian
	“preCambrian”

I tried to match the colors from the latest time scale from www.stratigraphy.org for the CGMW colors, and from the pdf linked below for the USGS colors

Hopefully no rocks on your map from the Cretaceous, Mississippian, or Cambrian come in contact with each other, they would be difficult to separate.

CGMW		USGS
	Cretaceous
	Mississippian
	Cambrian

How about Jurassic, Pennsylvanian, and Silurian?

CGMW		USGS
	Jurassic
	Pennsylvanian
	Silurian

Why even use colors to distinguish different Formations or Series if they are so similar to others?

Are the old Standards to be changed?
The USGS published some suggestions back in 2005.

USGS Colors (pdf)

And the Geologic Data Subcommittee (GDS) of the Federal Geographic Data Committee (FGDC)

published standards for GIS in 2008.
Are these going to change?  Will they use the random color system of the CGMW?

Some pages (just a few I've run across so far) already using the CGMW colors:
This map (from SVP) was modified from an existing map and strat column with the new colors.
Macrostrat using the new colors.

I think it is unfortunate that these new colors are being adopted, and it seems to me a step backwards.

Whine over :(