GENERAL50517

• Permit No: C1981026
• IBM Index Class Name: General Documents
• Doc Date: 10/29/1981
• Doc Name: Proposed Decision and Findings of Compliance
• Permit Index Doc Type: FINDINGS
• Media Type: D
• Archive: No

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General Geology
Stratigraphy and Structure
The general geology of the North Park region has been well-established by numerous
United States Geological Survey investigations, the most notable of which are
Beekly (1915), Hail (1965, 1968) and Kinney (1970, 1971).
The North Park region can be geomorphically classified as an intermontane area,
enclosed by the Medicine Bow Range to the east, the Park Range to the west, and the
Rabbit Ears Range to the south. The resultant structural basin, which is truncated
to the north by the Independence Mountain Fault, contains sediments ranging in
age from Triassic to Quarternary. These sediments are approximately 15,000 Peet
in total aggregate thickness. Late Cretaceous and Early Tertiary sediments account
for almost all of this total. Figure 2 is a generalized strati graphic column of
the North Park Coal Field.
In addition to the broad synclinal fold which formed the overall structural basin of
the North Park region, considerable local folding and faulting has also occurred.
These local folds and faults are probably the result of compression caused by the
formation of the larger synclinal trough. The McCallum Anticline is one of these
local folds. Geographically, the McCallum Anticline lies between the Michigan and
Canadian Rivers east of the town of Walden. Structurally, the anticline can be
categorized as doubly plunging and asymmetrical about its axis. To the north, where
the anticline plunges northwest, the strike is approximately N45°W. To the south,
the structure begins to change strike as the crest of the anticline plunges almost
due south. Except near both noses, the anticline tends to be asymmetrical, with
the more steeply dipping flank to the east side. In places, the sediments on the
eastern flank are near vertical or even overturned. Exhibit C-1 is a geologic
map of the McCallum Anticline and vicinity as interpreted by Xinney (1970, 1971).
Sebsequent glaciation and erosion have exposed the older sediments of the Upper
Sandy Member of the Pierre Shale Formation along the crest of the anticline, The
younger Coalmont Formation, which contains the Sudduth coal seam, is exposed along
both flanks of the anticline (see Exhibit C-1). tJyoming Fuel Company's Canadian
Strip mine is located on the eastern flank of the structure near the southern nose.
The proposed permit area will extend the present operation north along the western
flank.
Coal Geolo
The coal seams of the North Park area lie in the Coalmont Formation of Early Tertiary
Age (probably Paleocene or Eocene). The formation is composed of approximately
.~ 9,000-6,000 feet of interbedded shales, mudstones, sandstones, and coals which
unconformably overlie the Upper Sandy Member of the Pierre Shale Formation of Late
Cretaceous Age. Two major coal seams or zones exist within the Coalmont Formation
in the vicinity of the Canadian Strip mine. They are, in ascending order, the
Sudduth Seam and the Capron Seam. The Sudduth Seam is the thickest and most widely
developed seam in the region and is located at the base of the Coalmont Formation
resting on or near the unconformity on the Pierre Shale. The Capron Seam is
strati graphically located about 2,400 feet above the Sudduth Coal and is commonly
split into two beds. From an economic standpoint, the Sudduth Coal is more commer-
cially mineable than the Capron due to higher quality, and is the seam which is
recovered at the Canadian Strip mine, which varies from 10' to 23' thick. The
Sudduth coal seam produces a subbituminus B coal with a very low sulfur content of
0.25 and a heat output of about 10,800 BTU's per pound. All three mines in the
North Park coal Field are mining the Sudduth coal seam.
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