DALLAS COUNTY, TEXAS.
(Transcribed by Dorman Holub)
Of the large
number of counties in this great State of Texas, it is
universally conceded, not only by the citizens of the State,
but also by all passing immigrants, that for richness of soil,
congeniality of climate, charming and delightful scenery, a cultivated
and hospital people, Dallas county can not be surpassed. Truly
has it been said that she is the "banner county of the State."
Situated in the center of the northern
portion of the State, on what might be called a high rolling
plateau, it is bounded on the north by the county of Denton,
east by Collin and Kaufman, south by Ellis and west by Tarrant.
formation of the soil of Dallas county and of the strata beneath
belongs in geology to that period classed as Mesozoic time and
in the Cretaceous period, the lower division of this being uncrystaline
or of aqueous origin. There is a stratum of white limestone rock
beneath the deep, rich, loamy black soil, which appears universal
through the entire county. Sometimes it crops out and extends
for miles, scattering here and there, giving a mixed soil of
black with small white and greyish lime rocks. Especially is
this frequently seen in the western portion of the county.
SOIL AND OTHER PHYSICAL FEATURES.
This soil is very superiorly adapted
to the growing of small grains of almost every kind. Beneath
this limestone is sometimes found beds of gravel, which is most
conveniently utilized in improving roads and streets. These beds
are found to be of remarkable variation of depth and dimensions,
and must have been formed here when the waters covered the surface,
having been drifted hither and thither by the surging waters.
This gravel is lasting, as it consists chiefly of quartz, and
of course is never ground into powder when used, while the white
and grayish limestone found immediately beneath the soil crumbles
on being exposed to the elements, and of course is not only worthless
for paving roads and avenues but also for all building purposes
of any kind.
The very best of lime has been manufactured
out of this stratum of limestone, and, owing to this formation,
nearly all the springs and streams are of hard water. There are
exceptions, of course, as in the case of deep wells sunk beneath
the strata and where water is found in gravel or in a stratum
beneath that of the limestone.
There is what
is commonly, and most appropriately termed the "black strip"
of soil, about sixty miles in width, beginning at Red river,
the dividing line between Texas and the Indian Territory, sweeping
through Texas and extending almost to the Gulf of Mexico, and
embraces the richest and most productive soil in the State. Dallas
county is largely in this strip. While the surface consists in
the greater measure of rolling prairie most delightful to the
eye, especially when clothed in spring time with fresh green
verdure, it is traversed by cross timbers that cluster on the
banks of the Trinity river, which flows diagonally almost through
its center, also on smaller streams and ravines. The soil is
of that black, rich, loamy texture characteristic of the most
productive known to geologists, and in some portions of the county
it consists of that black, waxy character most charmingly adapted
to almost every product known to the Southern climate.
The rich, black soil sometimes extends
to the depth of four and five feet, and is said to never diminish
its strength in giving forth produce like that of the sandy or
clay-like soil. On this the finest vegetation grows. When this
county was unsettled the wild grass would grow to the height
of an ordinary man. It was proverbial that the hunter would sometimes
become lost in the grass and, straying off from his companions,
entail upon himself the greatest difficulty to find his bearings.
This grass was not entirely over the county, but only in some
sections. A heavy mat of turf, however, was extended over the
entire surface of the soil, especially on the prairies, and it
was so strongly matted, and the black, sticky soil so compact
that it was of the greatest difficulty to break it up so as to
make it arable for farming purposes. It was, therefore, common
to see the farmer in primeval days of the county with from six
to eight yoke of oxen, or with from four to six mules, hitched
to a large plow, breaking up his prairie lands, doing what was
commonly called "sodding;" but as the county became
more thickly populated and rains fell more frequently, thereby
moistening the surface, this task of "sodding" became
less irksome so much so that at the present period of development
it is common to see the farmer seated on his sulky plow, with
only two horses, plowing this wild land; in other words, sodding
his new lands. This soil, once thought to produce nothing with
any certainty but corn and cotton, has been found to contain
those elements and ingredients productive of all kinds of small
grains, and in fact almost every kind of vegetation known to
the Southern climate.
There is but
a small quantity of timber, comparatively speaking, in the county,
and that is found as stated, clustering on the streams, and,
while not adapted for building purposes, it affords great comfort
and convenience to the citizen for fuel in winter as well as
protection to stock from the cold blasts of the northern winds,
commonly called the "Texas Norther." This timber consists
of oak, sycamore, pecan, hack berry, walnut, cottonwood, red
and white elm, blackjack, box-elder, red haw, locust, hickory,
wild china, cedar, gum-elastic, ash and "bois d'arc"
(osage orange); and a peculiarity about it is, it does not grow
to a great height. It is mostly stumpy, except immediately on
the banks of the Trinity river. Here you find occasionally a
large cottonwood, elm or hackberry. This timber has also an undergrowth
called "underbrush," which makes it sometimes very
difficult to pass through.
At an early date, the farmers enclosed
their farms with rails and brush, hauled for miles from these
cross timbers, but as the population increased, and the timber
became more scarce, and dear in price, bois-d'arc hedges were
substituted, and afterward the barbed wire.
At the present
period of development, almost every farmer in the county has
his enclosure fenced with barbed wire. The introduction of this
wire was a great blessing to the people. In fact, it would have
been almost impossible for the people in the county to have gotten
along without it.
WATER COURSES, WELLS, ETC.
Cotton, corn, wheat, and oats, raised
per acre, in Dallas county, cannot be surpassed in any county
in the State. Truly might it be said that the quantity per acre
on some of the choice lands of this county, approximates that
of the richest soil in the Mississippi valley. The cotton stalk
is known to grow so high in placer, that a man can scarcely reach
to the top, and the limbs so heavy with bolls that they sometimes
break from the main stem. Corn and wheat are raised in great
quantities. All vegetables are grown with ease. Sweet and Irish
potatoes, sorghum, in fact almost all produce raised in a southern
climate are produced on this soil. The largest, sweetest, finest
quality of fruit, of almost every kind, such as peaches, apricots,
apples, grapes, cherries pears, plums, etc., are produced.
Watermelons are a marvel in size, in
their season. The average yield of wheat per acre is from fifteen
to thirty bushels; cotton from one-half bale to a bale, corn,
from thirty to seventy bushels; oats, from thirty-five to eighty
bushels; and hay, both native and cultivated, cannot be surpassed.
The Johnson and Bermuda grasses, and
millet, are raised in abundance. All of the above produce always
brings the very highest prices in the markets of the country.
is one of the best-watered counties in the State. Besides the
Trinity river, there is the Five-Mile creek, and the Ten-Mile
creek, so denominated because of the distance from Dallas, the
largest and central city in its borders.
Almost all these smaller streams merge
into the Trinity river. Beside these, there are many everflowing
springs. The people are supplied with water by wells, in which
any quantity can be secured by digging to only a shallow depth.
Very frequently, at the depth of from fifteen to twenty feet,
an abundance is secured. The wealthier citizens have flowing
artesian wells, which are at present becoming quite common in
this county. After boring down a few hundred feet, the artesian
water, as clear as a crystal, will burst forth, sometimes as
high as twenty feet above the surface. The water from the ordinary
wells, springs and creeks is principally from magnesian limestone,
and of course very healthful. That of the artesian wells is pure,
a little warm, but delightful, after remaining exposed to the
air a short while. Rain water in cisterns is used by many, and
more especially in pools, called "tanks," which are
denominated in the East as ponds. These tanks are commonly used
by farmers for stock. They dam up a ravine or dig a place in
some low spot on the prairie, so the water sometimes can bank
up for the distance of a half mile. This is a very common means
of securing water for cattle, and it was, indeed, more common
with earlier settlers than now, when long droughts visited the
county and lasted for several months. During the periods of droughts,
the people would drive their cattle for miles, to a neighbor's
tank. No such droughts now visit the county.
Almost the entire
time, during the summer season, a cool and delightful breeze
is blowing: so the temperature in mid-summer ranges from about
75 to 90 degrees. The nights are generally very pleasant, as
a cool and delightful gulf breeze prevails almost constantly.
A sunstroke here is very uncommon.
This county is superior in splendid facilities
for traveling by private
conveyance, in addition to the numerous railroads. The county
bridges, and all avenues, are in first-class order.
of Dallas county in 1890 was 67,003, showing the largest of all
counties in the State. It contains an area of 900 square miles,
and an assessed valuation of its property, in. 1890, of $35,849,000.
The lands are valued at from $10 to $50 per acre, the lands most
valuable, near the city of Dallas, at from $100 to $200 per acre.
As the preceding
sketch is a mere preliminary bird's-eye view of the section of
which we are writing, we now present a fuller view of the geological
character of the district in which Dallas county is situated.
THE BLACK PRAIRIE REGION
A thorough geological survey of northern
Texas has never yet been made, but we give the substance of the
surveys that have been made and published in the First Annual
Report of the Geological Survey of the State.
Dallas county lies in the Cretaceous
system, characterized by chalk formations. The two series of
rocks comprising this system occupy the area known as the Black
Prairie, the Grand Prairie and the two Cross Timbers, besides
unstudied areas in the eastern and trans-Pecos regions of the
To these strata the State owes a large
part of her agricultural and
general prosperity, for they are the foundation of the rich,
black waxy and other calcareous soils of this region, and in
addition to their, agricultural features they are the most productive
source of building material, while adjacent to the parting between
them, extending the entire length of the State and depending
upon their stratigraphy, is a remarkable area of natural and
artesian wells. That these formations are of great economic value
is also shown by the fact that they are the site of our principal
cities and the rich agricultural soils which surround them.
This is in general a chalky country,
and uniquely Texan, so far as the United States are concerned,
constituting a distinct geographic region in every topographic,
economic and cultural aspect, and one which should not be confused
with other portions of the country. It covers an area of over
73,512 square miles, or over one-fourth (28.27 per cent.) the
total area of Texas, forming a broad belt of fertile territory
across the heart of the State, from the Ouachita mountains of
the Indian Territory and Arkansas to the mountains of northern
Mexico, an area larger than the average American State, and equal
to the combined area of all the New England States.
One-third of this region lies north of the Colorado river, and
the remainder to the southwest.
This region, with its many different
prairies, each covered by its
peculiar vegetation, its sweeping plains and diverse valleys,
its undulating slopes clad with liveoak, its narrow strips of
cross timbers, its ragged buttes and mesas, presents a landscape
varied, yet possessing as a whole an individuality peculiarly
its own. All of these features, with their different tints and
tones of soil and vegetation, with their varied conditions for
human habitation, are but the surface aspects of the system of
chalky rocks (chalky sands, chalky clays and chalky limestones)
upon which it is founded, and to which is primarily due every
physical quality of the country. In fact it is the great chalky
region of the United States.
The rocks originated as sediments of
the Atlantic ocean, laid down with great uniformity during two
of the long epochs of subsidence and emergence when the waters
covered this region many hundred fathoms deep. These ancient
sediments are now more or less consolidated and elevated into
a fertile land, which is decomposing under atmospheric conditions
into soils and debris, and in turn being slowly transported to
the ocean, where it will make other rock sheets. They now occur
in regular sheets or strata, dipping beneath each other toward
the sea, while the projecting western edges, each of which weathers
into and imparts its individuality to its own peculiar belt of
country, outcrops in long, narrow belts, sub-parallel to the
present ocean outline. Thus it is that as one proceeds inland
from the coast. He constantly crosses successively lower and
lower sheets of these formations.
The oldest, or lowest, in a geological
sense, of these outcrops, forms the Upper Cross Timbers, those
above these make the Grand Prairie, the next sheet forms the
Lower Cross Timbers, and the next the Black Prairie, etc.
Each of these weathers into a characteristic
soil, which in its turn is adapted to a peculiar agriculture.
Each, too, has its own water conditions and other features of
economic value. Some of there rock sheets, like the Upper Cross
Timber country, may be comparatively infertile in the region
of outcrop, yet they may serve to carry the rain which falls
upon the thirsty sands far beneath the adjacent country, where
by artesian borings it becomes an invaluable source of water
supply for a distant and more fertile region.
The Cretaceous country of Texas, as a
whole, like the system of rocks of which the surface is composed,
is reparable into two great divisions, each of which in turn
is subdivided still further. These two regions are known as the
Black Prairie and Grand (or Fort Worth) Prairie regions, each
of which includes in its western border, north of the Brazos,
an elongated strip of timber known as the Lower and Upper Cross
occupies an elongated area extending
the length of the State from Red river to the Rio Grande. The
eastern border of the Black Prairie is approximately the southwestern
termination of the great Atlantic timber belt. The Missouri Pacific
and the International railroads from Denison to San Antonio approximately
mark the western edge. A little south of the center, along the
Colorado river, from Austin eastward to the Travis county line
near Webberville, the Black Prairie is restricted to its narrowest
limits. Westward this prairie is succeeded by a region of some
superficial resemblance to it which on closer study is found
to differ in all essential points. This is the Grand, or Fort
Worth, Prairie, or chard-lime-rock region."
The so-called mountains west of Austin
are the remains of the Grand Prairie. In general, the Black Prairie
region consists of a level plain, imperceptibly sloping to the
southeast, varied only by gentle undulations and deep drainage
valleys, unmarked by precipitate canons. It is transected at
intervals by the larger streams, whose deep-cut valleys, together
with their side streams, make indentations into the plain, but
not sufficiently to destroy the characteristic flatness of its
wide divides-remnants of the original plain, or topographic marine
base level, which has not been completely scored by its still
youthful drainage system. The altitude of the plain is between
600 and 800 feet. The surface of most of the Black Prairie region
is a deep black clay soil, which when wet becomes excessively
tenacious, from which fact it is locally called "black waxy."
In general it is the residuum of the underlying clays, and contains
an excess of lime, which, acting upon the vegetation by complicated
chemical changes, causes the black color. It is exceedingly productive,
and nearly every foot of its area is susceptible of a high state
of cultivation, constituting one of the largest continuous agricultural
regions in the United States. Large crops of cotton, corn, etc.,
are annually raised upon its fertile lands; and if there were
facilities for proper transportation it would soon be one of
the leading districts of our country.
The Black Prairie is subdivided
longitudinally into four parallel strips of country, differing
slightly, and distinguishable only by slight differences in topography
and in the underlying rocks. In the easternmost of these divisions
north of the Brazos and Colorado rivers, however, the sand is
hardly perceptible. Immediately interior of this is located the
largest and, most characteristic area which is marked by the
stiffest of the black waxy calcareous clay soils. Upon digging
through this stratum, the subtecture is found to consist of a
light blue or yellow calcareous clay, called by the residents
"soapstone" and Joint clay," from its jointed
and laminated structure. The surface, especially of t he high
undrained divides, is also accompanied in many places by minute
depressions known as I "hog-wallows," which are produced
by the drying, cracking and disintegrating character of these
excessively calcareous clays in poorly drained places.
This, the main portion of the Black Prairie,
constitutes fully two-thirds of its total area. The cities of
Greenville, Terrell, Corsicana and Kaufman are situated near
the border of the sandy and black waxy strips. Manor, Clarksville,
Cooper, Taylor and Temple are all situated in the main black
An outcrop of the "white rock"
or chalky country, forming a narrow strip averaging two miles
in width, from Red river to the Rio Grande, succeeds on the west
the main black waxy Strip. Thia chalk region is marked by a topography
more rounded and deeper incised, but still void of the sharper
lines of stratification that characterize the Grand Prairie region.
It is usually treeless, but occasionally marked by clumps of
handsome evergreens and oaks. The western edge of this chalky
region, as seen at Oak Cliff, near Dallas, at Sherman, Hillsboro
and other places, usually ends in an escarpment overlooking a
valley containing the minor Black Prairie and Lower Cross Timber
strips. It is upon this chalk that the most prosperous of the
interior cities of Texas are located, including Paris, Sherman,
McKinney, Dallas, Waxahachie, Waco, Austin, New Braunfels and
San Antonio, all of
which are dependent upon the agricultural products of the adjacent
West of the "white rock" or
chalky division, and generally at a slightly lower altitude,
occupying a valley across the State, is a second narrow strip
of black clayey land of a nature similar to that of the main
black waxy area, and likewise accompanied by hog-wallows. This
is the country east of Denton and Whitesboro, in the Mountain
creek district of Dallas county, and along the line of the Missouri
Pacific railway from Alvarado to Waco.
The Lower Cross Timbers (a narrow belt
of forest country extending from the Red to the Brazos rivers)
represent the westernmost strip of the Black Prairie region,
and belong to it geographically, as will presently be shown.
Let us now consider the substructure
of the Black Prairie region in five divisions, commencing with
the lowest, namely, the Upper Arenaceous, or Glauconitic; the
main Black Prairie, the surface of the marine clays, called the
Ponderosa marls, the white-rock division, which is the outcrop
of the Austin Dallas chalk, aggregating about 600 feet in thickness;
the minor Black Prairie, also composed of clays like those of
the main division, and consequently having a similar topography;
and the Lower Cross Timbers. All the foregoing rock sheets, between
which there is no Stratigraphic break, represent the sediment
deposited in the oceanic waters during a long continued subsidence,
geologically known as the Upper Cretaceous period, for which
collectively we have chosen the name of Black Prairie Series.
This Upper Cretaceous series has five conspicuous Stratigraphic
and lithologic divisions, which approximately correspond with
the topographic divisions of the Black Prairie above mentioned.
1. - THE LOWER CROSS TIMBER BANDS.
From the Brazos river northward to Red
river the base of the upper series is composed of a brown, more
or less ferruginous, predominantly sandy littoral deposit, resting
unconformably upon various horizons of the semi-chalky beds of
the Washita division, or top of the Comanche series. These sandy
deposits present an infinite variety of conditions of cross-bedding,
clay intercalations, lignitic patches, and variation in fineness
of size and angularity of the uncemented particles, characteristic
of typical littoral deposits, while occasionally there are found
In the vicinity of Denison these sands
are covered by a post-Tertiary sand, which confuses their identity
The Lower Cross Timber region abounds
in rich sandy roils, which support a vigorous timber growth,
this Structure being especially for deep-rooted plants, and are
specially adapted to fruit-growing, as seen near Denison and
Paris. There is also considerable lignite and iron in the beds
of this region.
The lignite is frequently discovered
and mistaken for bituminous coal. It is doubtful whether either
exists in sufficient quantities for commercial use. The Cross
Timbers are also in the line of the Central Texas artesian belt,
and it is probable that in any portion of its area an artesian
well sunk through the rock of the underlying Comanche series
would find an abundant flow of water. These .sands are also valuable
for water-bearing purposes, and the wells along the margin of
the minor Black Prairie area are supplied from them.
2. - THE EAGLE FORD CLAY SHALES.
These lie to the eastward and immediately
above the Lower Cross Timber sands, and are the foundation of
the minor Black Prairie streak.
Beneath the scarp of the white rock (Austin-Dallas
chalk) at Dallas, and extending westward through the Mountain
creek country to the Lower Cross Timbers, can be seen typical
localities of this division, the thickness of which is estimated
at 400 feet. These clays in their medial portion are dark blue
and scaly, highly laminated, and occasionally accompanied by
gigantic nodular septariae, locally called "turtles."
The uppermost beds gradually become more calcareous, graduating
rather sharply into the chalk. There are also occasional bands
of thin, impure limestones, which are readily distinguishable
from all other Upper Cretaceous limestone by their firmness and
lamination. Fossil remains of marine animals are also found in
clays, including many beautifully preserved species, the delicate
color and nacre of shells being as fresh as when the animals
inhabited them. Among these, oysters, fish teeth, chambered shells
and Inocerami are the most abundant.
The chief economic value of the minor
Black Prairie will ever be its
magnificent black calcareous soil, while some of the chief geological
considerations are the ascertainment of means to make this soil
more easily handled and less tenacious by devising suitable mixtures,
the discovery of road-making material, and the increase of water
for domestic and agricultural purposes. Owing to its clay foundation
the soil now retains for plant use treble the quantity of moisture
of some of its adjacent sandy districts, but surface and flowing
water is scarce. Fortunately, however, this district is also
within the Central Texas artesian well area, and an abundant
supply of water can always be had at a depth of less than 1,500
feet, as has been proved in the course of our investigations.
When this fact is fully appreciated the region will be one of
the most prosperous in Texas.
In the valleys of most of the streams
running eastward across the east half of the minor Black Prairie,
artesian water can be obtained at from 100 to 300 feet. The source
of this water is in the Lower Cross Timber sand. Many of the
concretions and calcareous layers are probably Suitable for making
cement; but tests must be made. The clays may also prove of commercial
3. - THE WHITE ROOK, OR AUSTIN-DALLAS
Immediately above and to the east of
the Eagle Ford clays comes the white rock, or Austin-Dallas chalk,
which is the most conspicuous representative division of the
whole Upper Cretaceous system. This occupies the narrow strip,
as noted in the preceding topographic description, marking the
western border of the main Black Prairie region, separating it
from the minor Black Prairie. The outcrop of this chalk begins
in the southwest corner of the State of Arkansas and in the Indian,
Territory. It crosses Red river, the exposure continuing westward
up to the south. side of the valley of that stream to the north
of Sherman, from which place it deflects southward, passing near
McKinney, Dallas, Waxahachie, Hillsboro, Waco, Belton, Austin,
New Braunfels, San Antonio and Spofford Junction, beyond which
it bends northward, appearing in the disturbed mountains in the
vicinity of El Paso and New Mexico. It is distinguished. above
all by its
peculiar chalky substructure.
The words "limestone" and "chalk"
are used on these pages as follows:
Limestone is employed generically for
species of widely different origin and structure, namely, of
five kinds: 1. Breccias composed of more or less comminuted and
cemented shells of ancient bottoms or shores. 2. Concretions
or segregations formed by the segregation of lime in clays and
sands after original deposition, rare in our rocks. 3. Chalks
are composed of amorphous calcium carbonate, usually more or
less foraminiferous, void of laminations, and of comparative
deep-sea origin. These may be hardened by metamorphism into firm
limestones. Hence the term "chalky limestones" will
imply chalky origin. 4. Laminated, impure limestones, occurring
as alternating beds in sands and clays, indicative of shallower
origin then chalk. 5. Metamorphosed limestones, or any of the
above which have undergone induration or secondary change. All
laminated limestones thus far found in the Texas Cretaceous are
in the basal beds, and are more or less arenaceons or argillaceous,
further proving their origin to have been in shallower water
than those in which chalk is laid down.
The rock of the Austin-Dallas chalk formation
is a massive, nearly pure, white chalk, usually free from grit
and easily carved with a pocket-knife. Under the microscope it
exhibits a few calcite crystals, particles of amorphous calcite,
and innumerable shells of foraminiferae. The air-dried indurated
surfaces are white, bat the saturated subterranean mass has a
bluish white color. The rock weathers in large conchoidal flakes,
with an earthy fracture.
In composition it varies from 85 to 94
per cent. of calcium carbonate, the residue consisting of magnegia,
silica and a small percentage of ferric oxide.
The thickness of this chalk is about
500 feet. So far as observed in
Texas it averages the same thickness at Austin, Sherman and Dallas.
It is of great uniformity throughout its extent; but there are
a few local differences in hardness, which are sometimes due
to surface induration and to igneous action, having been converted
into marble in some places.
A great portion of the former extent
of this chalk has been destroyed by erosion, and its western
border in Central Texas is now receding eastward under the influence
of excessive atmospheric decomposition and denudation.
The group may have extended at one time
all the way to the Rio Grande. This formation abounds in fossils,
most of which, however, are but poorly preserved casts.
The economic advantages of the white
rock are various. It affords good locations for the building
of cities and communities, not only on account of the firm foundation
for building and road-beds and good drainage which it always
affords, but also on account of its sanitary conditions, produced
by the irnbibing capacity of the chalk. When accurate statistics
are kept, it will be proved that dwellers upon the chalky lands
have a great hygienic advantage over those upon sands and clays.
The chalks are also water-bearing, and while yielding their moisture
slowly they afford an abundance for domestic purposes, and play
an important part in the transmission of the rainfall to depths
from which it can be abstracted, perhaps, in east Texas, by artesian
wells. This chalk is also valuable for the manufacture of whiting,
rouge, etc. Chalk is most used in England,
however, where scientific agriculture has attained its highest
development for dressing lands. Thousands of tons are used annually
on the non-ealcareous lands of England, where it is usually applied
at the rate of twenty tons per acre, just as it will ultimately
be used upon the non-caleareous lands of east Texas as Boon as
our agriculture advances to a stage where its necessity will
Chalk makes a cheap, convenient land
dressing for non-chalky lands, performing in a more satisfactory
manner the functions of quick-lime in making available other
constituents of the Boil, besides contributing to it minute but
valuable proportions of phosphates, potash and other plant foods.
The chalk will also prove of great use
in the manufacture of Portland cements. It is the material used
in the manufacture of most of the imported cements; and when
the people of this State properly appreciate what an immense
industry lies at their doors-a natural, Texas monopoly-this region
will become a great cement center for the United States.
4. - THE EXOGYRA PONDEROBA MARLS.
The name given to these marls is that
of a large fossil oyster, which occurs in immense quantities
in certain beds.
The eastward continuation of the Austin
Dallas chalk is covered by what is the most extensive and valuable,
but least appreciated, geological formation in the United States,
namely, a remarkable deposit of chalky clays, aggregating some
1,200 feet in thickness, according to reported well-borings and
estimates of the normal dip. In fact these clays are so little
known that no popular name has yet been accorded them; and hence
they are called after the immense fossil oyster found in them.
These clays occupy the whole of the main
Black prairie region east of the Austin-Dallas chalk, and form
the basis of the rich, black, waxy soil. Notwithstanding their
horizontal extent, good outcrops of the unaltered structure are
seldom seen, owing to their rapid disintegration. Usually they
are seen only in ravines, creeks, or fresh diggings. They are
of a fine consistency, unconsolidated and apparently unlaminated
until exposed to the weather, when their laminated character
is developed. They are light blue before atmospheric exposure,
but rapidly change into a dull yellow, owing to the oxidation
of the pyrites of iron in them. Their chief accessory
constituent is lime in a chalky condition, and they are more
calcareous at the bottom than at the top. Near the top of these
and other exposures there is to be seen a rapid transition into
the black, calcareous, clay soil, characteristic of chalk and
chalky clays whenever their excess of lime comes in contact with
vegetation. They are more calcareous and fossiliferous at their
The economic value of these chalky clay
marls is in the fact that they are the foundation and source
of the rich soil of the main black, waxy prairie, the largest
continuous area of residual agricultural soil in the United States,
apparently inexhaustible in fertility; for as the farmer plows
deeper and deeper he constantly turns to light the fertile marls
which renew the vitality of the surface. These soils can be much
improved by further geologic study.
5. - THE UPPER ARENACEOUS OP. GLAUCONITIO
This is the continuation of the Ponderosa
marls, exhibiting itself chiefly in northeastern Texas and southwest
Dallas county also borders upon the Grand
prairie or Fort Worth section, the features of which are reported
at length by the State Geologist, so far as studied; but as it
comes outside of our district, we omit it here.