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Samuel Washington McCallie.

A preliminary report on a part of the phosphates and marls of Georgia online

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was replaced by lime phosphate, without obliterating the original
structure.

The late Prof. W. C. KJerr, formerly State Geologist of
]S r orth Carolina, ascribes the origin of the South Carolina phos-
phates to a small bivalve shell, belonging to the genus lingula.
These shells are found, more or less plentiful, at a number of
points along the eastern coast of the United States. They contain



34 ORIGIN OF PHOSPHATES

from 40 to 50 per cent, of lime phosphate, which corresponds very
closely to the composition of bone. It appears quite plausible, that
these shells should have existed in such great quantities, at one time,
in the sea near Charleston, as to give rise to the phosphatic material,
which, upon being dissolved by rain-water, replaced the carbonate of
lime in the marl-beds, which were, in turn, broken into fragments and
rounded, either by the action of waves or by running water, and finally
deposited, as w r e now find them.

It was suggested, by Prof. C. U. Shepard, in 1869, 'that the phos-
phatic material originated from the droppings -of birds. He compares
its formation to the guano deposits, now taking place on the Mosquito
coast of the Caribbean Sea.

A number of similar theories have also been advanced, to account
for the phosphate deposits of Florida. Mr. !N". H. Darton, of the
IT. S. Geological Survey, thinks, that they originated from deposits of
guano. According to this theory, during, probably, the early Mio-
cene, the whole eastern coast of Florida, from Tallahassee to Char-
lotte Harbor, was, for a long period of time, a favorite resting place
for innumerable sea-birds, that frequented the coast. The excrements
of these birds, having accumulated along the shore, in great quantities,
were finally leached out, by carbonated rain-water, and carried below,
where they phosphatized the underlying limestone.

Dr. IN". A. Pratt has suggested, that the phosphatic material orig-
inated from the remains of f oraminif era, which had the power of se-
creting phosphate of lime from the sea-water, in the same manner as
lime carbonate is now being formed, by the coral polyps, off the south-
ern coast of the State. It has been urged against this opinion, how-
over, that there is, at present, no f oraminifer known, which secretes a
skeleton of phosphate of lime, nor has there, yet, been discovered any
fossil remains of these animals, having such a chemical composition.



ORIGIN OF PHOSPHATES 35

It is the opinion of Dr. Francis "Wyatt, author of the book, entitled
Phosphates of America, that the Florida phosphates originated,
mainly, from the Vicksburg limestone. The formation is known to
contain, throughout its different layers, more or less phosphatic ma-
terial, originally from organic remains; is usually of a porous nature;
and is supposed to have been permeated by acidulated waters, which
dissolved the lime carbonate, and carried it away in solution, while the
less soluble phosphates were left behind. This residual phosphatic
material was finally drifted, by the waves and currents into depres-
sions, crevices and irregular weathered cavities in the limestone, where
it now forms more or less extensive deposits.

The observations of the writer, on the Eocene and the Miocene
formations of Florida and Georgia, appear to confirm Dr. "Wyatt' s
theory, as to the origin of the phosphates. He frequently found,
embedded in the limestones -and marls, belonging to these periods,
numerous remains of vertebrates. These fossils are quite conspicuous
in the limestone near Faceville, Decatur county, Ga., where they
make up a considerable portion of the rock^nass.

Both the rock and the pebble phosphates are thus referred to a com-
mon origin, while the peculiar form of the latter is accounted for, by
the action of the waves, or by running water. Associated with these
pebbles, are numerous remains of mammals and other animals.
These fossils frequently occur in great abundance; and they have
been considered, by some, to be the original source of much of the
phosphatic material, found within the limits of the State.

The presence of these remains is explained, on the theory, which,
however, seems unsupported by any well-established facts, that during
the Glacial period, great numbers of land and other anim'als were
driven south, by the extreme cold, to perish on the Florida penin-
sula.

Perhaps the latest theory, concerning the deposition of the Florida



36 ORIGIN OF PHOSPHATES

phosphates, and one, that deserves the most attention, by reason of
the author's extensive knowledge of the deposits, has recently been
advanced by Mr. Geo. H. Eldridge of the IT. S. Geological Survey.
He refers the formation of the soft and the hard-rock phosphates to
three different periods. The first period, in which the primitive rock
was formed, he describes as follows: - "This stage began, probably,
not later than the close of the Older Miocene and within the Eocene
area it may have begun much earlier. Whether the primary phos-
phate resulted from a superficial and heavy deposit of soluble guano,
covering the limestones, or from the concentration of phosphate of
lime, already widely and uniformly distributed throughout the mass of
the original rock, or from both, is a difficult question. In any event,
the evidence indicates the effect of the percolation of surface waters,
highly charged with carbonic and earth-acids, and thus enabled to
carry down, into the mass of the limestone dissolved, phosphate of
lime, to be redeposited under conditions favorable to its separation.
Such conditions might have been brought about, by the simple inter-
change of bases, between the phosphate and carbonate of lime, thus
brought together, or by the lowering of the solvent power of the wa-
ters through loss of carbonic acid. The latter would happen, when-
ever the i acid was required for the solution 'of additional carbonate of
lime, or when, through aeration, it should escape from the water.
The zone of phosphate deposition was evidently one of double concen-
tration, resulting from the removal of the soluble carbonate, thus rais-
ing the percentage of the less soluble phosphate, and from the ac-
quirement of additional phosphate of lime, from the overlying por-
tions of the deposits. The thickness of the zone of phosphatization in
the Eocene area is unknown; but it is doubtful, if it was ever twenty
feet. In the Miocene area, the depth has been proved, from the phos-
phates in sight, to have been between 6 and 12 feet.



ORIGIN OF PHOSPHATES 37

"The second period includes the secondary depositions, brought
about, mainly, through sedimentation, in cavities of the primitive
rock. The deposits of phosphate, formed, during this period, which
was long continued, and finally closed, by some physical change, were
quite free from iron and aluminum.

"The third period includes the time, during which the deposits, pre-
viously formed, were broken up; and their fragments were redepos-
ited in the form, in which they are now found. These changes are
supposed to have taken place, about the time of the last elevation of
the peninsular above the sea-level."

Mr. Eldridge tihinks, that the phosphate was 'Originally derived from
the remains of birds, mammals, marine animals and, possibly, also,
from chemical precipitation. It is supposed, that the sea-water, at
some remote period, contained much more phosphate of lime than at
present; and there appears to be no satisfactory Teason, he suggests,
for its not having been deposited, under certain conditions, in the
same manner, as calcium carbonate and other minerals. The porous
Eocene -and Pliocene limestones are pointed out, as presenting favora-
ble conditions, for rapid solution, by the acidulated waters, and the
concentration of their phosphatic material.

Dr. Safford, has advanced the following theories, to account for the
origin of the Tennessee phosphates:

"The phosphate bed of Swain creek, and of other creeks as well, not
unfrequently contains fish remains, especially of jaw-bones. Fragments
of bones, as wide as one's hand and ten inches long, have been col-
lected. Smaller fragments are quite common. The rocks of middle
Tennessee, be it remembered, are made up of matter, once deposited
from the waters of ancient seas. The sea, which was a chief factor, in
giving us the members of the Black Shale group, was of great extent,
reaching from Arkansas and Missouri to the eastern border of Penn-



38 ORIGIN OF PHOSPHATES

sylvania and New York. From this sea, in the course of long ages,
were deposited the clays, sands and limy material, but chiefly clays,
that made up the series of strata, with which we are now especially
concerned. There were, also, during much of the same time, condi-
tions existing, which, as will be seen, led to the depositions of phos-
phatic material and debris. All were dropped and accumulated on the
bottom of the sea the clays, sands, limy materials and, in a smaller
measure, the phosphates. The sea, during this time, was the home
of a prolific fish life. Fishes abounded throughout its great extent.
Some of them, clothed with heavy armor, after the fashion of a heavy
iron-clad, and of great size and fearful strength, were monsters, and
easily rulers, of the sea. They have been named placodemis, a word
meaning plated or cuirassed hide. In addition, sharks were plentiful,
and fought with the cuirassed placoderms for supremacy. Then, there
were multitudes of small fry, together with a quota of phosphate-
bearing mollusca.

"Here we recall the fact, that the main phosphate lies immediately
under the Black Shale, appearing to have close associations with it, an
association, or the thought of it, strengthened by the further observa-
tion, that, now and then, a layer of phosphate occurs interstratified
with the layers of shale. There is, thus, reason, for believing, that
they have, in some measure, a common history, and that both are of
the Devonian age. The fishes lived, multiplied and held their own,
for a time, then died and passed into decay, scattering all, that was
lasting of them, over the sea-bottom. Fish eat fish; hence their ex-
crements contained largely comminuted bone and like matter, and are
themselves a fair phosphate.

"In Ohio, all the refuse bone and excrements, from these ancient
races, are diffused through hundreds of feet of strata. In Tennessee,
during the same long ages, there was, on the one hand, only a mini-



ORIGIN OF PHOSPHATES 39

mum of clay and sand deposited; but, on the other, just as much fish
refuse. There, it is disseminated through a great vertical thickness of
shales; here, it is concentrated in a thin bed, with little or no shale;
concentration of this kind, we are inclined to believe, has been a fac-
tor in giving to Tennessee its remarkable beds of phosphate.

"Thus it would appear, that for a long time, during the first of the
fish era, as we may call it, when the shales in Ohio were accumulating,
there was no clayey deposition in Tennessee; and therefore, no shale
was found. During this time, phosphate debris, gathered in Ten-
nessee, was washed and transported by oceanic currents, and widely
and thinly distributed over the sea bottom; but locally, perhaps, in
eddies, heaped up in thick deposit, now, the veritable bonanzas of rock
phosphate. This done, a time followed, when the waters of the sea,
bearing light changes of clayey and organic matters, invaded our south-
ern latitudes; and, unloading their burden, covered the phosphate
scantily with the sediment, which is now the Black Shale."

"Another view, as to the source of phosphate of calcium in the phos-
phate bed, is as follows: - It has been maintained, that the mineral
has been derived, primarily and chiefly from the minute shells, so
often spoken of. These occur, in parts of the phosphate, in great
numbers. Pieces of the rock have been seen, that were wholly made
up of the casts of their interiors. With them, too, are the worn
teeth. While mostly calcareous, some of the shells are known to
have had more or less phosphate in their composition. This is cer-
tainly true of a flat, comparatively large, tongue-shaped shell, often
associated with the others, and named lingula.

"For this view, it is argued, that, while the fish remains and debris
occur, they are not abundant enough, to account for the- accumula-
tion of such a store of phosphate, as we find in the rock. At Comer's
mines, for example, in Totty's Bend, the bed rarely shows a fish-bone,



40 ORIGIN OF PHOSPHATES

while the shells abound. Again, by this theory, we can account for
the phosphate in the lowest, or the limestone bed. Plenty of shells
are seen in it; but, so far, no fish remains. Furthermore, the bed has
been shown to be Trenton; and no large fish bones are known, as yet,
in the Trenton, at least in Tennessee."

In speaking of the phosphate deposits of Cambridge, England, Prof.
T. Gr. Bonney has the following to say, concerning their origin:

"With regard to the mode of formation of these phosphatic casts,
nodules etc., we have to consider, not only the probable source of the
phosphate, but also the mode, in which it has been concentrated into
these "coprolites." Phosphate of lime, in the form of apatite is pres-
ent in granite, gneiss, slate, talc and chlorite schists, and several kinds

of lava It is, also, present, in the waters of

numerous mineral springs. ...... It has been detected in

the waters of several rivers, and is probably present in all, as well as in
the sea, though of course in small quantities. Again, phosphates
(chiefly lime) are present in marine and other plants. In short, the
various investigations, that have been made, show, that it is almost
universally present in organic, and, not unfrequently, in inorganic
bodies

"Next, it has been shown, by numerous experiments, that phos-
phate of lime is soluble in carbonated water, and further, that phos-
phate of lime, present in an organism (plant or animal), is much more
soluble, than that in a mineral. '. V. ' .' :'. . Again, phosphate of
lime, dissolved in carbonated water, is precipitated by ammonia, which
is a result of decomposition of organic bodies. It appears then, to me,
that the best explanation of these phosphatic nodules is to consider
them formed, by what, for want of a better name, we may call con-
cretionary action. The excreta, softer tissues, and smaller bones of
the Yerte'brata, the bodies of numerous Invertebrata, many of which



ORIGIN OF PHOSPHATES 41

have left no other trace behind, the various marine plants, which prob-
ably flourish abundantly in a shallow sea, to say nothing of any
apatite, which might be present in the detritus, wherein they were
entombed,' would furnish a considerable supply of phosphates; in fact,
coeteris paribus, a shallow sea appears to me more likely to be rich
in phosphates, than a deep one. The phosphates of the more perish-
able parts of the above named organisms would be dissolved, in the
water permeating the mud of the sea bottom, which would, also, be
supplied with carbonic acid from decomposition, and so the mud be
saturated with a weak solution of phosphate of lime. Now, if at a
certain point in the mud, there were an excess of phosphate of lime,
and, especially, if ammonia were being evolved at that point, the
phosphate in the neighboring solution might be precipitated; and,
probably (for it seems to have often happened with other minerals),
all the phosphates of the surrounding mass would be precipitated
about the nucleus. I regard, then, these nodules, as the result of 'a
process, which took place, during a part of the Gault period, and was
continued, during the Greensand epoch, which began, shortly after
the death of the organisms, and lasted for a long time; and I explain
their abundance, as I have already said, by considering the seam of
the riddlings of a considerable deposit. It is noteworthy, how often a
bed of phosphate nodules comes just above a more or less marked
stratigraphical break. It appears to me, therefore, that the progress
of formation of these nodules is . ... . very analogous to that
of flint both, in many cases, proceeded from the mineralization of
sponges.

"It may not unfairly be asked, why, seeing, that weak solutions of
phosphate of lime must be almost always present in sea- water, are not
phosphate nodules generally present in rocks? The answer to this



42 ORIGIN OF PHOSPHATES

is, that the phosphate nodules are far from rare, and that the difficulty
is exactly of the same kind, as exists in the formation of flint.

"It may be, that local circumstances, as indicated above, have been
favorable, to slightly concentrating the phosphatic element in the
sea-water; but, without availing ourselves of this possibility, we may
fairly answer, that 'the process of deposition from weak solutions, one,
of which we are very ignorant, is probably a complex process, which
requires several independent conditions to be fulfilled; so that it is but
rarelv, that all are satisfied."



CHAPTER III



DISTRIBUTION OF PHOSPHATES
IN GEORGIA



Ever since the discovery of phosphate in Florida, it has been the
prevailing opinion of many persons, that these deposits extend north,
and would likely, at some time, be found in paying quantities, along
the various streams and in the numerous swamps, of the border coun-
ties of South Georgia. This belief, in many instances, has caused the
planters of the region to become generally interested; and frequent
reports have been current, from time to time, of extensive and valua-
ble discoveries, in several localities. During the spring of 1894, the
writer visited South Georgia, to investigate these various reports, and,
at the same time, to make an examination for deposits of marl. It
was my good fortune, to have with me, for the first few days, Mr.
Geo. H. Eldridge of the U. S. Geological Survey. Mr. Eldridge,
who had spent three seasons in Florida, studying the phosphate de-
posits of that State, gave me much valuable information, concerning
the nature of the deposits, and advised me, how to proceed with the
work, in order to obtain the best practical results. Only about six
weeks were spent in the field in South Georgia, the first season. Dur-
ing the following spring, the work was again taken up, and continued,
until all the, counties, bordering on the Georgia-Florida state-line, to-
gether with some of the counties of the Atlantic coast, were examined.
The plan, adopted in the work, consisted of a pretty thorough exam-
ination of almost all the natural and artificial exposures of rocks and

(43)




44 DISTRIBUTION IN GEORGIA

marl-beds, reported in these counties. Chemical tests were made in
the field, on all rocks, which were supposed to contain phosphoric
acid; and, where its presence was found, in considerable quantities, the
deposit was further studied, with reference to its economic impor-
tance, and samples were taken, for a complete analysis. Typical fos-
sils were collected, wherever found, in order to establish the geological
horizon, and, if possible, to correlate the different formations with the
Florida deposits.

As it is almost impossible, for persons, not familiar with phosphate,
to distinguish some of its forms from the different varieties of
limestone, or chert, it was deemed best, to visit, as far as prac-
ticable, all the rock exposures. Much time was thus consumed, in
examining outcrops which proved to have but little or no commer-
cial value. This, however, seemed to be the only feasible way, of ob-
taining the necessary data, for a reliable report. The swollen condi-
tion of the rivers, in a few instances, seriously interfered with our
making a satisfactory examination of their beds and banks. With
these exceptions, the work was sufficiently complete, to give a general
idea of the deposits, in the several counties traversed, and at the same
time to establish, with a considerable degree of certainty, the truthful-
ness or falsity of the various current reports, concerning the discovery
of valuable beds of phosphate in that region.

The topography of the region under consideration, has the general
appearance of a plain. At only a few points, does it attain an eleva-
tion, of more than 300 feet above tide-water. Much of the area is
practically level; and it is occasionally traversed, by cypress swamps,
or series of lime-sinks, which frequently form chains of beautiful
lakes, that add variety to the otherwise monotonous landscape. In
places, notably the greater part of Brooks, Thomas and Decatur coun-
ties, the surface becomes quite rolling, and resembles, in a somewhat



DISTRIBUTION IN GEORGIA 45

general way, the rolling portions of North Georgia. The streams- are
all sluggish, with no well donned valleys. In the more elevated
areas, they have cut deep channels, exposing, in places, bluffs, from
30 to 60 feet in height. The bluffs commonly lie adjacent to long
stretches of low palmetto lands, which become flooded, during the
rainy season. Large springs, that appear to be the outlet of small sub-
terranean rivers, are frequently met with. They commonly occur,
in the vicinity of lime-sinks, with which they seem to be intimately
connected.

The soils of 'South Georgia, along the Florida state-line, may be
divided, for convenience, into two classes, the sandy and the clayey
soils. The former is much more abundant, than the latter, and, also,
less productive. The natural growth of the sandy soil consists mainly
of long-leaf pine, dwarf palmetto and wire-grass. When first cleared,
these soils produce good crops of cotton, sugar-cane, potatoes etc. ; but,
owing to their porous nature, the plant-foods are soon leached out, and
almost continuous fertilizing is afterwards necessary, in order to keep
up their original fertility. While this may be stated, as a general
rule, applying to all the sandy soils, there are, however, some very in-
teresting exceptions. These exceptions consist of certain fields, which
have been under almost constant cultivation, for many years, anct
which still retain, to a remarkable degree, their former productive-
ness. An examination of some of these fields showed, that there are
scattered through the soil numerous small sandstone boulders or peb-
bles, whose cementing material consists mainly of phosphates of lime.
Thus, the continuous fertility of these fields is undoubtedly due, in a
general measure, to the slow disintegration of these boulders, and a
gradual liberation of the phosphate, which has become a perpetual
source of plant-food.

The clayey soils are found, in the more elevated areas; and they are



46 DISTRIBUTION IN GEORGIA

both* fertile and durable. They are locally known, as hummock
lands ; and they were originally heavily wooded with oak, hickory and
other species of hard woods. These lands yield, without the aid of
fertilizers, good crops of corn, cotton, oats etc., besides pears and
various other fruits.

The geological formations, occurring in the various counties visited,
consist of the Columbia and Lafayette, together with certain portions
of the Miocene and Eocene. Both the Columbia and the Lafayette
are superficial deposits of sands and clays, extending over the entire
area, and forming the 'above named soils. The Miocene and the Eo-
cene formations, which consist principally of limestone, chert and
marl-beds, are rarely exposed, except along the larger streams, and in
the numerous lime-sinks. The boundary line, separating the out-
cropping of these two latter formations, has never been accurately de-
termined. Dr. Spencer, formerly State Geologist of Georgia, in his
report for 1890, covering the western part of this area, maps the
northern half of Decatur county, and also the northwestern corner of
Thomas county, as Eocene, the boundary line passing a short distance
south of Bainbridge and near Eorest Falls. My own observation
shows, that the white limestone, the upper beds of the Eocene forma-
tion, extends much further to the east, underlying the Lafayette, in
the greater part of Thomas and Brooks counties, the eastern boun-
dary extending, in places, as far as the "Withlacoochee river, or even
beyond.



DECATUK COUNTY



The greater part of Decatur county, lying between the Chattahoo-
chee and Flint rivers is practically level; and only a few opportunities



DISTRIBUTION IN GEORGIA 47

are ottered, throughout this wide stretch of piney woods, to study the
formation, underlying the superficial layer of sand. Spring creek, a
stream of considerable size, traversing the center of the area, has, at
different points along its course, outcroppings of rock, that were ex-


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Online LibrarySamuel Washington McCallieA preliminary report on a part of the phosphates and marls of Georgia → online text (page 3 of 7)