Sedimentary Features and Mineralization fo the Salt Wash Sandstone at Cove Mesa, Carrizo Mountains, Apache County, Arizona: Technical Report for April 1, 1953 to March 31, 1954 Page: 20
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20
repetition of the sandstone units:
No. of Drill Holes
2-cycle sections (301-401 thick) 13
3-cycle sections (501-701 thick) 36
4-cycle section (651-851 thick) 3.
The predominance of the three-cycle section at Cove
Mesa is further corroborated by field observations of the
Salt Wash sandstone exposed on the sides of the Mesa,
where three prominent "rims" occur in the section. As
may be expected, those drill holes which encounter four
cycles of deposition occur in the topographically higher
portions of the mesa, where the Salt Wash sandstone is
thicker.
Details of these sections as observed in figures 9-18
indicate that the units usually begin at the top with a
shale or siltstone, followed by a thin sandstone unit,
usually 5-10 feet thick, and below this member a massive
sandstone 9-15 feet thick, containing minor shale breaks.
These units are believed to correspond to the two types
of sandstone previously described from the surface ex-
posures. There are, however, many logs which show an ab-
sence of the thin sandstone and in these instances the
thick massive units are separated by shales from two to'
four feet thick.
The individual examples of detailed logs and cyclic
correlations shown in figures 9 to 18 merit some discus-
sion. Figure 9 illustrates a log of drill hole Co-4, in
the extreme northern portion of the mesa, where the sec-
tion is primarily composed of a sequence of four massive
sandstones whose overall similarity in gamma-ray log
properties is shown.
The log of drill hole Co-12, figure 10, indicates
three repetitive sections of rapidly alternating sand-
stone-shale intervals, with an underlying massive sand-
stone in each cycle, while figure 11 shows another triple
cycle, Co-30, composed of massive, thick sandstones, con-
taining a number of distinctive and correlatable shale
breaks.
A different type of cyclic section is shown in the
log of core drill hole #176, figure 12. In this example,
the two major cycles of deposition each consist of an
upper sandstone, 8 feet thick, separated by a thin shale
break from a lower more massive sandstone 14 to 15 feet
thick. This type of depositional sequence suggests the
two principal types of sandstone observed at the surface
exposures.
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Jones, Daniel J. Sedimentary Features and Mineralization fo the Salt Wash Sandstone at Cove Mesa, Carrizo Mountains, Apache County, Arizona: Technical Report for April 1, 1953 to March 31, 1954, report, March 1954; Washington, D.C.. (https://digital.library.unt.edu/ark:/67531/metadc783663/m1/20/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.