GENERAL48878

• Permit No: C1981014
• IBM Index Class Name: General Documents
• Doc Date: 6/24/1994
• Doc Name: PROPOSED DECISION & FINDINGS OF COMPLIANCE FOR RN2
• Permit Index Doc Type: FINDINGS
• Media Type: D
• Archive: No

the Pierre is a sequence of thin, inter-bedded sandstones and
mudstones.
The Trinidad Sandstone, directly above the Pierre Shale, outcrops
about 1.0 miles east of the mine site and is composed of massive
buff to yellow sandstones ranging from 40 to 90 feet in thickness.
The Trinidad Sandstone is indicative of a prodeltaic depositional
environment.
The Vermejo Formation overlies the Trinidad Sandstone and is the
coal-bearing unit of mining interest to the Southfield operation.
The Vermejo Formation consists of a complex network of mudstones,
siltstones, sandstones and eleven coal seams, all indicative of a
vast fluvial delta and plain sequence. The coals developed in the
back water swamp areas of the river delta. The coal seams of
economic importance in the area are: Monarch, Red Arrow, Jack
O'Lantern, Vento, Manley and Rex Carbon. Total thickness for the
Vermejo sequence is approximately 925 feet.
The coal seams mined at the Southfield Mine are two of the six
principal seams present in the Vermejo Formation; the Red Arrow and
the Jack O'Lantern. The Red Arrow seam ranges in thickness from 4
to 7 feet and is a moderate to high sulfur coal with 3 recognizable
units separated by bony layers of ash. The Jack O'Lantern seam is
a low sulfur coal which ranges in thickness from 4 to 8 feet and
also consists of 3 recognizable units separated by boney ash
layers. The permittee has provided a complete coal, roof and floor
analysis in the permit. For further information refer to Section
2.04.6 of the permit.
Ascending upward on the stratigraphic column from the Vermejo
Formation is the Raton Formation, a unit consisting of two members;
a basal sandstone and muddy-sandy layer. The Raton averages 650
feet in thickness. The erosional base of this unit marks the top
of the Vermejo Formation in the Southfield mine area. There are no
coal-bearing units found in the Raton, since its character
indicates that a period of increased uplift and subsequent erosion
in the area followed that of the depositional low-energy
environment found in the Vermejo.
Uncomfortably overlying the Raton Formation are the sediments of
the Poison Canyon Formation. Similar in composition and character
to the Raton, the Poison Canyon Formation is coal barren and is 200
feet in thickness of alternating beds of mudstone and sandstone.
Covering most of the topographic ridges in the Southfield mine area
are a series of Pleistocene boulder/colluvial/alluvial deposits.
Most of the boulders consist of gneiss, schist and sandstones
derived from erosion and mass wasting of the Wet Mountain uplift to
the south and west. Depositional thicknesses range from 5 to 100
feet in places near the mine site, with 20 feet recorded in the
loadout area of the mine.
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