Information Circular 107


Inclusions and small vacuole trains which
suggest a plutonic origin, whereas others exhibit
abundant vacuoles and have vermicular
inclusions of chlorite suggesting a hydrothermal
origin (Folk, 1980).
 The second most abundant quartz type
present is monocrystalline, undulose quartz,
making up 42.8 percent of the total, followed by
semi-composite, 5.6 percent, and fully-composite
grains, 3.6 percent. Semi-composite grains are
composed of two or more suborystals having
very close optical orientation with a distinct break
between subcrystals; however, the extinction
shadow is not observed to sweep smoothly
across the grain during petrographic analysis.
Fully-composite grains have two or more
subcrystals with strongly undulose extinction and
distinct crenulate boundaries (Young, 1976; Folk,
1980). Semi-composite grains are more
numerous than fully-composite grains in all core
material examined, except the Shell Oil
Company core (Florida permit 647) where a
slight reversal in frequency occurs. Small,
needle-like inclusions of rutile are seen in all
types of quartz.
 Most of the quartz grains examined in this
study are subrounded to rounded. Additionally,
many grains have overgrowths, some being
abraded Indicating recycling.
 The second most abundant detrital mineral of
the Denkman Member is feldspar, which ranges
from 15.9 percent to 46.5 percent and averages
26.3 percent throughout the study area.
Potassium feldspars orthoclasee and minor
amounts of microcline) are the most abundant,
ranging from 55.0 percent to 100 percent and
averaging 87 percent of the feldspar fraction
(Figure 6). Plagioclase feldspar ranges from 0
percent to 32.0 percent, averaging 13.0 percent
of the total feldspar population. In order of
decreasing abundance, the feldspars are
orthoclase, plagioclase, and microcline, with
untwinned orthoclase making up the largest
fraction. Most grains appear similar to quartz in
size and rounding. Many feldspars are
sericitized, possess mineral Inclusions, and have
quartz intergrowths in graphic patterns.


Overgrowths are common on both potassium
and plagloclase feldspars.
 Feldspar grains have been subjected to a
variety of weathering processes, with many
showing signs of multiple processes. Most
appear to be related to dissolution and
replacement of grains (Figure 7). The most
common form of weathering is vacuolization, of
which the magnitude ranges from slight to
extreme. About 45.0 percent of all feldspars
show some sign of vacuolization. The author
makes a distinction between degrees of
weathering. In the case of "slight" vacuolization,
weathered grains appear cloudy due to pin-point
dissolution. Severely weathered grains on the
other hand, are seen as partially or totally
dissolved grains and make up about 8.0 percent
of the total feldspar population. A few grains,
generally less than 2.0 percent of the total
feldspar population, appear unaltered.
 Other forms of feldspar alteration were
observed, but all were secondary to vacuolization
in frequency of occurrence. Limonitization was
the next most abundant form observed in all
samples followed by phyllosilicate replacement.
The dominant form of phyllosilicate replacement
is chloritization, but kaolinitization and illitization
also occur. In the Smackco Ltd. well (Florida
permit 1096), considerable chloritization of
feldspars is present of which the magnitude
appears to increase with depth. Dolomitization of
feldspars was the next most often observed form
of feldspar weathering followed by calcitization,
anhydritization, and pyritization.
 Rock fragments within the Denkman range
 from 3.0 percent to 26.0 percent, averaging 12.2
 percent. Metamorphic rock fragments (MRFs)
 are the most abundant averaging 80.0 percent of
 the total rock fragment population. The next
 abundant fragments are volcanic rock fragments
 (VRFs), 15.0 percent, followed by sedimentary
 rock fragments (SRFs) at 5.0 percent.
 An aphanitic grain type of varying composition
 and texture is the most abundant rock fragment
 present (Figure 8). Initially, some difficulty
 developed in identifying these grains because of
 their resemblance to chert. The grains were