D E T R I T A L Q U A R T Z AS AN I N D I C A T O R OF D I S T A N C E F R O M S H O R E IN
MARINE MUDROCKS l
HARVEY BLATT
School of Geology and Geophysics
University of Oklahoma
Norman, Oklahoma 73019
AND
MATTHEW W. TOTTEN
K. & E. Petroleum, Inc.
Wichita, Kansas 67202
ABSTRACT: Eighty-nine surface samples and 17 subsurface samples of shale from the Blaine Formation
(Permian) in western Oklahoma were examined to detemLine the variation in percentage of quartz and mean
size of quartz with distance from a known shoreline. Samples were fused using sodium bisulfate to release
the quagz from the mass of clay minerals.
The surface samples gave areally and statistically meaningful trends; subsurface samples did not do so
because of sampling difficulties. The mean percentage of quartz in surface samples decreases from 47
percent at a distance of 60 km from shore (more precisely, the sand-mud line) to l I percent at 270 km
from shore (r = .70), a loss of l0 percent quartz with each 60 km increase in distance. Mean grain size
decreases from 5.2,5 at 60 km from shore to 6.9d0 at 270 km from shore (r = .71). Extrapolation of the
data indicates that at the sand-mud boundary the percentage of quartz is 57 percent and the mean size of
the quartz is between 4.75d~ and 5.1d~.
The percentage of quartz in mudrocks can be a useful indicator of the position of the shoreline in ancient
fine-grained epicontinental sea deposits.
INTRODUCTION AND PURPOSE
Approximately two-thirds of the stratigraphic column consists of mudrocks, many
of which were deposited in the shallow epicontinental seas that covered large parts of the
cratons during Phanerozoic time. Typically,
these laterally extensive fine-grained rocks appear to be homogeneous throughout the length
and width of the depositional basin. No method
currently exists to determine either the distance from the shoreline or the contour of the
shoreline in such deposits although several
methods have been tried.
Most attempts have concentrated on the clay
mineral fraction of modem muds, for example, studies of decrease in clay mineral " s i z e "
in the offshore direction (Gibbs, 1977); studies
of increased boron content in more saline
waters (Couch, 1971); and studies of changes
in clay mineralogy with increased salinity
(Meade, 1972). None of these methods has
produced satisfactory results. The best that can
~Manuscfipt received April 10, 1981; revised May 28,
1981.
be said is that a particular method may work
in one area but fail in another area. This result
is to be expected for several reasons. Clay
minerals are not carried offshore as individual
flakes but rather as porous floccules whose
diameter and specific gravity are set by their
mineral composition, crystal size, and the salinity of the sea water (Krank, 1975). In addition, these floccules are rapidly compacted
by a few meters of overburden and lose their
identity soon after deposition. With burial to
depths of a few thousand meters the clays are
recrystallized (Hower et al., 1976) so that the
size distribution at the time of deposition is
destroyed (Weaver, 1980).
It is clear, therefore, that an attempt to determine distance from shore in an ancient mafine mudrock will have to concentrate on the
nonclay mineral fraction, the quartz and feldspar. These minerals remain essentially unchanged from the time of deposition, although
small amounts of very fine-grained quartz are
produced in mudrocks during the diagenetic
change from smectite to illite (Yeh and Savin,
1977). It is also possible that some detrital
orthoclase and microcline are destroyed during
JOURNALOF SEDIMENTARYPETROLOGY, VOL. 51, NO. 4, DECEMBER, 1981, P. 1259--1266
Copyright © 1981, The Society of Economic Paleontologists and Mineralogists 0022-4472/81/0051-1259/$03.00
1260
HARVEY BLATT AND M A T T H E W W. TOTTEN
clay mineral diagenesis to supply potassium
for illitization of smectite, although this is still
uncertain. In either event, however, feldspars
form less than 15 percent of the quartz-plusfeldspar fraction of the average mudrock (Shaw
and Weaver, 1965) so that the possible loss of
some feldspar during diagenesis is not lethal
to the hypothesis we wish to test. The purpose
of this study is to determine the gradient of
decrease in percentage and grain size of quartz
with increasing distance offshore in an ancient
marine mudrock.
PREVIOUSSTUDIES
Most studies of ancient mudrocks and modem muds emphasize clay mineral composition
and areal distribution. Few studies do more
than note that quartz (or feldspar) is present.
Exceptions to this generalization are the investigations by Devine et al. (1973), MOiler
and Stoffers (1974), and Kolla and Biscaye
(1977). Devine et al. (1973) determined mineral distribution patterns in the surficial muddy
sediments of the Gulf of Mexico in water
depths greater than 200 m. In the area offshore
of the Mississippi River delta they found that
the percentage of detrital quartz, on a carbonate-free basis, decreased from a maximum of
43 percent about 80 km offshore in a water
depth of 1,000 m to a minimum of 23 percent
300 km offshore at a water depth of 3,500 m.
Kolla and Biscaye (1977) determined the distribution of quartz in surficial sediments of the
Indian Ocean. They found a decrease in percentage of quartz offshore of the major river
systems, the Ganges-Brahmaputra and the Indus, but the gradient of decrease is indeterminate from the large-scale map in their publication. The data of Mi.iller and Stoffers from
the Black Sea (1974) also are on too large a
scale to be useful for our purposes. There is
no published study of the distribution of quartz
( ~ feldspar) with distance from the shoreline
in an ancient mudrock.
B L A I N E F O R M A T I O N (PERMIAN}, WESTERN
OKLAHOMA
In choosing a suitable mudrock unit for our
investigation, we required several criteria to
be satisfied. 1) The mudrock must be marine.
2) The stratigraphy of the unit must be well
understood. 3) The geologic age of the unit
should be precisely known so that all samples
can be of penecontemporaneous age. 4) The
position of the shoreline must be well established from existing stratigraphic and paleontologic data. 5) The unit must crop out over
a wide geographic area to permit adequate
sampling. These requirements are satisfied by
the Blaine Formation in western Oklahoma.
The Blaine Formation is a redbed sequence
of fine-grained clastics and gypsum that crops
out in a north-south band for more than 400
km (Fig. 1). Its maximum thickness is 60 m
but typically it ranges between 35 m and 40
m. Two persistent beds of gypsum, one in the
middle of the formation, the other at the top,
divide the Blaine into two parts. The Blaine
represents only part of Guadalupean time, certainly less than 15 million years and possibly
very much less, but more accurate dating is
not now possible. The position of the southern
half of the eastern shoreline during the period
of Blaine deposition is reliable to within -+20
krn and was established using palynomorphs
(Clapham, 1970) and information on sedimentary facies from Clifton (1944) and Hills
(1942). The shoreline position is speculative
in the northern half of the study area because
of erosion. The position shown in Figure 2 is
simply extrapolated linearly from south to
north.
METHOD OF INVESTIGATION
One hundred six samples of shale were collected, 89 from outcrops and 17 from bags of
chips recovered from wells in the Anadarko
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I~G. l.--Palcogeography and pnncipal facies in relation to the outcrop pattern of the Blaine Formation in the
middle Permian Basin of southwestern United States
(modified from Johnson and Denison, 1973). AB is the
location of the Anadarko Basin.
DETRITAL QUARTZ DISTANCE INDICATOR
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KILOMETERS
FIe. 2.--Areal variation in the percentage of quartz in
Blaine shales in relation to distance from a shoreline established using palynologic and lithofacies data. A single
sample point on the map may represent several samples
located too close to each other to be separable at the scale
of the map.
1261
part fused using the sodium bisulfate technique
described by Blatt and Schultz (1976). The
fusion destroys all constituents of the shale
except quartz and feldspar and does not affect
either the amount or the grain size distribution
of these minerals. X-ray diffraction analyses
of the fused material were performed from
several sites throughout the study area to verify that only quartz and feldspar were present.
Comparison of areas under the major X-ray
peaks in Blaine Formation samples with areas
in artificial standards indicated that the feldspar content of the samples approximates 5
percent in all samples.
The size frequency distribution of the fused,
weighed samples was determined using standard sieves at 0.54 intervals down to 4.54 (43
~m) and micromesh sieves for smaller sizes.
Micromesh sieves used were 54 (30 Ixm),
5.64 (20 ~m), and 6.64 (10 ~m). The sediment finer grained than 10 ~m was assumed
to have a minimum size of 1 i,tm so that cumulative frequency curves could be extrapolated to 100 percent. The graphic mean was
calculated for each sample using the formulas
of Folk and Ward (1957).
RESULTSAND DISCUSSION
Percentage of Quartz
Basin (Fig. 1) drilled in search of petroleum
and natural gas. The stratigraphic position of
each outcrop sample was noted in relation to
the gypsum bed that divides the Blaine into an
upper and lower part. Subsequent laboratory
analyses revealed no significant difference in
quartz content or grain size between the two
parts.
Subsurface samples were taken from well
cuttings, the stratigraphic position determined
by inspection of electric logs. Because contamination of the sample is possible from other
formations higher in the hole, red mud chips
that appeared to be from the Blaine were handpicked from each subsurface sample. Nevertheless, it is likely that contamination was not
eliminated completely because the difference
in color between the shales in the Blaine and
those in the overlying units is small.
A small piece of each sample (approximately 2 gm) was fragmented using a rubber
pestle until it passed through a 2.54 sieve. The
fragments were divided into equal parts using
a riffle splitter, weighed to 0.5 mg, and one
The areal distribution of quartz percentage
(Fig. 2) shows a general parallelism with the
published shoreline determined using palynology and sedimentary facies, but the pattern is
not as regular as might be wished elsewhere
on the map. It seems likely that the bulk of the
non-parallelism between the ancient shoreline
and contours of quartz percentage results from
two factors: 1) imprecision in sampling in the
west-central part of the study area (subsurface
samples); and 2) the speculative position of the
shoreline in the northern part of the area,
where erosion has removed the nearshore sediments. In the southern half of the area, the 50
percent through 20 percent contours, which
are well established by outcrop samples, seem
satisfactory. They bulge systematically in a
westerly direction, reflecting the low-lying
landmass of the Wichita Mountains during
Permian time (Johnson and Denison, 1973).
In the center of the map, west of the 30 percent
contour, there is a great deal of "noise" in the
data, probably because the subsurface samples
were all chips carried up from depth by the
1262
HARVEY BLATT AND M A T T H E W W. TOTTEN
circulating drilling fluid. Apparently our attempt at hand-picking Blaine shale chips from
the sample bag of red shale chips collected by
the well-site geologist was only partially successful. As noted earlier, the shales stratigraphically above the Blaine differ in color
only slightly from Blaine shales. In the northern part of the map area, the data seem to reflect the presence of a marine (deltaic) accumulation of mud or a cratonic shoreline position
and orientation different from the one we assumed.
Figure 3 shows the relationship between the
percentage of quartz and distance from the
shoreline for the surface and for the subsurface
samples of Blaine shale. A strong correlation
is present between quartz percentage and distance for the surface samples (r = .70, P =
.999), with the percentage of quartz decreasing linearly by 10 percent for each 60 km increase in distance from the shoreline. The
regression equation is Y = - 0 . 1 7 X + 57.13.
The r-value of .7 indicates that about 50 percent of the estimated percentage of quartz depends on factors other than distance from
shore.
Our surface samples were collected at dis-
+
r.
"I 7.
+
~.,~
tances from the shoreline ranging from 60 km
to 270 kin. Extrapolation of the data indicates
that at the shoreline or, more precisely, the
sand/mud line the sediment will contain 57
percent quartz and 43 percent clay (including
minor amounts of organic matter, hematite,
carbonate, and heavy minerals).
Extrapolation of the data in a direction away
from the shoreline indicates zero percent of
quartz at 336 km (95% confidence limits =
± 15 km) offshore. However, there always will
be at least a few percent o f quartz in marine
muds and mudrocks because small amounts of
very fine-grained quartz are carried to the sea
floor far from shore in lightweight porous clay
floccules. In addition, winds blowing seaward
will carry small amounts of silt-size quartz into
the basin of deposition.
The regression line based on the 17 subsurface samples is poorly defined (r = .26) and
the percentage of quartz at the shoreline is projected to be only 31 percent. As suspected,
based on the map of areal distribution of
quartz, the subsurface samples were highly
contaminated by fragments of red shale from
Permian rocks higher in the stratigraphic section in western Oklahoma.
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40
60
80
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p,.
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DISTANCE (KILOMETERS)
FIG. 3.--Percent quartz versus distance from shore in surface and subsurface shale samples from the Blaine Formation. Only the data points for the surface samples are shown.
DETRITAL QUARTZ DISTANCE INDICATOR
1263
Mean Grain Size of Quartz
shoreline. At a distance of 336 km from the
The areal variation in mean grain size of shoreline, the point at which the mean percent
quartz (Fig. 4) shows a pattern very similar to of quartz goes to zero (F!g. 3), the mean size
that shown by the percentage of quartz. The of the quartz predicted by Figure 5 is 7.474
effect of the Wichita landmass is quite prom- (5.6 ~m).
The data from the 17 subsurface samples
inent at the southern end of the map, as is the
high level of " n o i s e " in the central area where once again form a poorly defined regression
the position of the contour lines is determined line (r = .25).
by subsurface samples.
The mean grain size of quartz in the surface Correlation Between Quartz Percentage and
Mean Size
samples of Blaine shales decreases linearly
with increasing distance from shore (Fig. 5)
Blatt and Schultz (1976) established that a
according to the equation Y = 0.0081X + strong correlation exists between the percent4.75 and the correlation coefficient of .71 is age of quartz in mudrocks and the mean grain
significant at the .999 level. Extrapolation of size of the quartz. Spears (1980) found that the
the regression line to the shoreline results in ratio TiO2/A1203 in mudrocks increases lineara mean grain size of 4.754 (37 ~m). This ly with increasing percentages of quartz, revalue is a reasonable estimate of the boundary flecting the same correlation. The Blaine shales
between the traction transport characteristic of follow the same pattern (Fig. 6) with a corsands and the suspensions from which muds relation coefficient o f . 72 and a regression line
are deposited. Davies and Ethefidge (1975, p.
Y = - 1 5 . 8 5 X + 124.47.
249) reported a similar size for a composite
sample of the quartz grains in Mississippi delta At the shoreline the percentage of quartz is 57
muds immediately adjacent to the modern percent and, therefore, the mean size of the
quartz is 5.14 (from a regression equation with
K ~, N S A 5
"-------7"
size as the dependent variable). Our data indicate that the best estimate of the mean grain
J
,
I size of quartz at which the mineral should disI
appear from mudrocks is 7.94 (4 Ixm) in con'
/ trast to the value of 9.14 (2 ~m) projected by
/
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Blatt and Schultz (1976).
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DISPERSAL MECHANISM
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o SUBSURFACESAMPLE
KILOMETERS
FIG. 4.--Areal variation in mean grain size of quartz
(d~) in Blaine shales in relation to distance from a shoreline established using palynological and lithofacies data.
A single sample point on the map may represent several
samples located too close to each other to be separable
at the scale of the map.
The results of this study demonstrate that
there exists a strong and geologically useful
relationship among the percentage of quartz,
the mean size of quartz, and the distance from
shore in shales of the Blaine Formation. During Blaine deposition, selective sorting occurred in sizes at least as small as 7.24 (7
~m). Gibbs (1977) has shown that sorting can
be effective with grains as small as 1 ~m.
Two types of processes might explain the
trends in percentage and size of the quartz
grains in the Blaine shales. The first of these
is hypopycnal (hypo = less than; pycno =
dense) plane jet flow of sediment-laden river
water into a salt-water basin, a phenomenon
that occurs at the mouths of most large rivers
(Bates, 1953; Wright and Coleman, 1974).
The muddy fresh water has a lower density
than the sea water and is visible as a brownish
layer coveting the underlying clear sea water.
HARVEY BLATT AND MATTHEW W, TOTTEN
1264
7 -(17 subsurface samples)
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Y =.0081X i- 4.75
O0
r=,71
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20 40 60 80 I00 120 140 160 180 200 220 240 260
DISTANCE
(kilometers}
FIG. 5.--Mean size of quartz versus distance from shore in surface shale samples from the Blaine Formation. Only
the data points for the surface samples are shown.
The horizontal surface between the fresh water
and sea water is very stable and little vertical
mixing occurs for tens or perhaps hundreds of
kilometers outward from the shoreline. Hypopycnal flow would be most effective in a
depositional basin lacking strong onshore or
longshore surface currents.
The second process that might result in the
areal patterns of quartz grains that are present
in the Blaine shales is relatively dilute, finegrained turbidity currents on a submarine sediment cone, possibly generated by debris flows
(Hampton, 1972, 1975; McCave, 1972). Debris flows are known to occur on the Mississippi delta and elsewhere (Stuart and Caughey,
1976).
Eolian transport of terrigenous sediment into
ocean basins occurs in all parts of the world.
However, its effect on the textural relations of
shallow marine sediments such as those in the
Blaine sea probably is slight. Analyses of
eolian dust in the lower atmosphere over the
modem oceans by Aston et al. (1973) revealed
that quartz comprises only 3-7 percent of the
dust. This is much less than the percentage of
quartz in the Blaine shales. In addition, Windam (1969) studied atmospheric dust deposited in several permanent snowfields and determined that the mean size of the quartz
particles was consistently less than 5 p,m. Only
a very small percentage of the quartz in the
Blaine shales is this small.
CONCLUSIONS
The percentage of quartz and the mean grain
size of quartz in surface samples of shales of
the Blaine Formation can be used to detennine
the distance from the shoreline in this study.
The results of this study appear to have acceptable precision for geologic purposes as indicated by the following facts.
1) Extrapolation of our data indicates that
at the sand-mud line the composition of the
sediment is 57 percent quartz and 43 percent
clay (Fig. 3) and the mean size of the quartz
is 5. l~b (Fig. 6). These values seem reasonable
for sediment at the boundary between traction
DETRITAL QUARTZ DISTANCE INDICATOR
60
÷\+
of the slope of submarine fans in ancient basins.
What are the limitations of this method of
estimating shoreline position in ancient basins?
÷
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44
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5
6
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1265
7
SIZE
8
9
FIG. 6 . - - P e r c e n t quartz versus mean size of quartz in
Blaine shales. The regression line o f Blatt and Schultz
(1976) is s h o w n for comparison.
transport and suspension transport. Extrapolation of the regression line relating mean
grain size of quartz to distance (Fig. 5) results
in a prediction of 4.75d# (37 txm) at the sandmud line, a value substantially the same as the
5.1 cb (29 Ixm) obtained using the other plots.
2) The areal distribution of both the percentage of quartz and the mean size of quartz
accurately reflects the location and extent of
the land area of the Wichita Mountains, which
was low-lying during deposition of the Blaine
shales.
The mechanism that produced the observed
relationships between distance from shore and
both grain size and percentage of quartz probably is dilute, fine-grained turbidity currents
initiated by subaqueous debris flows. The rate
of decrease of size and percentage should be
related to the slope of the marine depositional
surface, and therefore future refinements of
the technique we used may permit estimates
1) The need for either extensive outcrops or
precision in subsurface sampling is clear. Because the Blaine Formation is overlain by
other red shales we were unable to identify
successfully pieces of Blaine Formation among
the red shale chips brought up by the drill. In
other areas and with other formations, however, this limitation may not be present, for
example, in studying a gray shale in a section
of red shales.
2) The bisulfate fusion technique becomes
inaccurate in proportion to the percentage of
very calcic plagioclase in the samples. Although there is no significant loss of potassic
and sodic feldspars caused by the fusion,
10-30 percent of plagioclase in the andesine
through bytownite compositional range normally is destroyed by the fusion process (unpublished studies in our laboratory). This loss
could seriously affect the results of studies in
depositional basins along convergent plate
margins where calcic feldspars may form a
large part of the sediment.
3) In deeply buried mudrocks, such as those
of Tertiary age in the Gulf Coast, a considerable percentage of the potassic feldspar in the
sediment may be lost during the diagenetic
conversion from interlayered smectite/illite to
illite. The importance of this effect certainly
will vary among basins and its overall importance is still uncertain.
4) During the conversion of smectite/illite
to illite, some quartz is produced as a byproduct. Probably this quartz is small in both
amount and grain size but precise quantitative
data are lacking. A large amount of diagenetic
quartz could introduce a great deal of noise
into the original depositional trends.
5) It is possible that noise could also be
added to the data by storms within the depositional basin, particularly in shallow epicontinental basins. The high correlation coefficients we obtained in the Blaine Formation,
however, suggest that storm effects are not a
serious problem. The extensive interbedded
gypsum units within the formation indicate
that the shales we studied were very shallowwater deposits.
6) Finally, it is possible that local sources
1266
H A R V E Y B L A I T A N D M A T T H E W W. TOTFEN
of silt-size quartz might be very restricted in
size variation, precluding the use of the technique we used. For example, loess deposits
have a restricted size range. In general, however, sources of silt-size quartz are so diverse
that all sizes should be present in most drainage basins.
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