Information Circular 107


grouped together as low-rank MRFs on the basis
of their unifying characteristics. The grains
usually appear dark-colored, resistant to
deformation, and silicified. A possible clue to
their origin is suggested by some of these grains
possessing small, highly birefringent, phyllosi-
licate inclusions and microlayers, which may
suggest an originally argillaceous texture.
Another possible source is indicated by several
grains examined from the Mesa Petroleum
Company core (Florida permit 551). Within the
Mesa core, many silicified VRFs closely
resemble some of the low-rank metamorphic
grains. This resemblance is increased where no
phenocrysts appear within the VRFs (Figure 9).
However, because of the pervasive alteration of
original grain fabrics, the author prefers to group
these aphanitic grains as low-rank MRFs.
 The second most abundant type of rock
fragment present is high-rank metamorphic
grains with a fabric of stretched and sutured
quartz subcrystals separated by thin mica plates
[Folk's (1980) schistose metamorphic] (Figure
10). The remaining rock fragments (in
decreasing order of abundance) are: VRFs,
slate/phyllite, another type of high-rank
metamorphic rock fragment [Folk's (1980)
stretched metamorphic], and traces of chert,
dolomite, and shale.

 MATRIX AND CEMENTS

 As a whole, the Denkman Member of
panhandle Florida is virtually matrix-free except
as observed in the Smackco Ltd. well core
(Florida permit 1096). X-ray diffraction data from
samples of this core indicates that chlorite and
illite comprise the majority of the matrix. Minor
amounts of euhedral dolomite are also present
within the matrix.
 Quartz overgrowths are the most abundant
cement type present within the Denkman. The
overgrowths can be subhedral to euhedral,
multiple in occurrence, with some being abraded
and recycled (Figure 5).
 The second most abundant cement present is
feldspar, occurring as overgrowths. Authigenic


phyllosilicate cements follow in abundance
consisting of pore-lining chlorite, illite, and
kaolinite. Clay content increases with depth and
is most abundant in the Smackco Ltd. well
(Florida permit 1096).
 Carbonate cement occurs most often at the top
of the section, just below the Smackover-
Norphlet contact. Calcite occurs 15.0 percent of
the time as opposed to dolomite occurring 11.0
percent of the time. Locally, dolomite may be
more abundant than calcite. Calcite is usually
seen as a pore-filling cement surrounding
framework grains. Calcite also occurs as
poikilotopic patches where framework grains
appear to float within the cement crystal.
Dolomite is usually seen as isolated or
interlocked mosaics of euhedral rhombs.
 Anhydrite cement is minor throughout the
section and usually seen as poikilotopic masses
which may form visible spots in the sandstone.
In at least one sample from the Smackco Ltd.
well, doubly terminated quartz crystals occur
within an anhydrite nodule. Hematite and
pyrite are both minor constituents of the cement
fraction, with hematite occurring as coatings on
some grains (Figure 10). Pyrite occurs as blebs,
euhedral crystals, and rosettas of probable
replacement origin within many framework
grains. The presence of pyrite within tightly
cemented quartz sandstones suggests that sour
gas (H2S-saturated gas) invaded the capillary
pores of the sandstone, converting the hematite
grain coatings to pyrite (McBride, 1981).

 Red Bed Lithofacies

 The relatively clean sandstones of the
Denkman Member become reddish-brown with
depth and grade into underlying red beds. These
red beds which include sandstones, siltstones,
and shales, become the dominant Norphlet
lithology in parts of Alabama (Mancini et al,
1985).
 Two wells containing red bed lithofacies were
examined for this study: the Champlin Petroleum
well (Florida permit 518) and the Mesa
Petroleum Company well (Florida permit 551).


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