1988-04-11_PERMIT FILE - C1981008A ‎(5)‎

• Permit No: C1981008A
• IBM Index Class Name: PERMIT FILE
• Doc Date: 4/11/1988
• Doc Name: Nucla East Geology and Overburden Assessment
• Section_Exhibit Name: Tab 6 Attachment 6-1
• Media Type: D
• Archive: Yes

elevation of these drilling sites are also provided in the specified appendices. The
location of the Nucla East drill holes are shown on Exhibit 6-7, Geologic Cross Section
and Sample Locations.
Structure. The Nucla East study area is located slightly north of the axis of the
structurally simple Nucla Syncline. Structure contours drawn as the top of the Lower
Dakota (#2) coal seam indicate that the mean coal dip is 4.5 percent southwest and strike
N. 450 W. Minor local variations in the attitude of these coals occur due to spuriously
trending small folds and penecontemporaneous depositional features. These slight
undulations are best seen in the highwalls and mine floors of active and abandoned mine
pits in the existing Nucla Mine permit area. The outcrop patterns and configuration of
overburden thicknesses are determined by a combination of topography and geologic
structure. Four geologic cross sections, D-DI through G-G', are shown in Exhibits 6-8
through 6-11 . Cross sections D-DI and E-El are oriented approximately parallel to the
mean coal strike while cross sections F-F' and G-G' are drawn nearly parallel to the mean
coal dip. These cross sections illustrate the simple structural relationships existing in
the Nucla East study area.
Faults have not been observed during the course of mining at Nucla Mine. According to
Cater (1955), faults are generally absent along the axial portions of synclines in the
Salt Anticline Region. It is possible that faults with small displacements exist, but
their occurrence is not yet documented.
Stratigraphy. With the exception of unconsolidated Quaternary deposits, the only exposed
formation at the mine site is the Dakota sandstone. The general lithologic
characteristics of this formation were described in the section on Regional Geology. This
section discusses the site-specific stratigraphy as derived from drill hole descriptions
and field examination of highwalls and road cuts.
Figure 6-1-1, Generalized Columnar Section of the Dakota Sandstone at the Nucla East Study
Area, and Exhibits 6-8 through 6-11, Geologic Cross Sections, show the complex lithologic
relationships within the study area. Figure 6-1-1 was prepared using information obtained
by geologists, hydrologists, and soil scientists during the baseline studies conducted
during 1986 and 1987. Stratigraphic correlation of individual driller's logs in Exhibits
6-8 through 6-11 proved to be difficult, and at times, confusing because of the wide
variation in driller's terminology. Only the principle stratigraphic units (i.e., coal
seams, sandstone, shale, etc.) were correlated in these cross sections.
6-1-6 Revised 04/11/88