USA > Alabama > Hand-book of Alabama. A complete index to the state, with map > Part 33
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TABLE OF GEOLOGICAL FORMATIONS.
QUATERNARY
OR POST- TERTIARY.
Soils and alluvium.
Biloxi or coast formations.
River terraces (second bottoms). (Ozark sands.
Lafayette sands and pebble beds.
Pascagoula and Grand Gulf formations.
. TERTIARY OR CENOZOIC.
f Vicksburg ] white limestone.
Jackson Claiborne. Buhrstone.
Hatchetigbee.
Bashi or Wood's bluff.
Tuseahoma.
Nanafalia.
Naheola.
Sucarnochee.
Clayton or Rutledge.
OR SECONDARY MESOZOIC.
Cretaceous
Eutaw.
Tuskaloosa.
Jura->Ic
Wanting in Alabama.
Tria tic .
Wanting in Alabama.
Permian Wanting in Alabama.
Coal Measures.
CarbonIferen4
( Mountain limestone, Oxmoor sandstone
ter.
St. Louis or Huntsville, Lauderdale (Keokuk).
Devonlan Black shale.
Silurian
Clinton or Red mountain, Trenton or Pelham limestone. Knox dolomite and chert.
Choecoloeco or Montevallo shales, including the Weisner quartzite.
Cambrian
( Coosa shales.
.
Archs.an.
Crystalline schists.
In giving the details concerning these formations, it will be, for many reasons, most convenient to consider them in historical order.
P Ches-
Sub-Carboniferous ..< and shale.
PRIMARY OR PALEOZOIC.
Ripley. ) Rotten limestone.
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GEOLOGY OF THE STATE.
CRYSTALLINE SCHISTS. - ARCH.EAN.
These rocks occupy a somewhat triangular shaped area in the eastern part of the State, bounded by a line running ap- proximately as follows : From the Georgia line. near the north- eastern corner of Cleburne eounty, southwestward through Clay and Coosa into Chilton, and thence eastward through Elmore, Tallapoosa, Macon and Lee to the Georgia line again, about opposite Columbus. These rocks differ from the other rocks of the State in being made up of distinct, often well crystallized minerals, of which quartz, feldspars, micas, and hornblende form the great mass of the rocks in question, while subordinated to these, other minerals occur, either forming rock varieties of limited distribution, or as ores of valuable metals, as minerals of economic value, or otherwise of interest.
As before stated, the great mass of these crystalline rocks are aggregates of the minerals, quartz, feldspar and mica, often associated with hornblende. Of these the quartz and horn- blende alone sometimes form great rock masses. Granite, gneiss, mica schist, quartzite and hornblende schist, or slate, are the most abundant of these rocks, while soapstones, or steatites, and limestones, are of much more limited occurrence. They are all disposed in beds of varying thickness, which are seldom in horizontal position, but are usually tilted at some considerable angle to the horizon, the dip or slope of these beds being prevalently to the southeast, while the trend or strike of their upturned edges is, as a rule, to the northeast and south- west. In crossing this country from the northwest to the southeast, it can not fail to strike the observer that, as he ap- proaches the southeastern border, he has evidences of con- stantly increasing amount of decay among the rocks. Along this southeastern border they are often nothing more than stratified clays, which are the result of their decay from the action of the atmospheric forces. This decay often reaches to a depth of fifteen or twenty feet from the surface, as may be seen in many of the railroad cuts. In these clays, ledges or thin sheets of quartz, which is practically unaffected by the weather, may be seen protruding; or broken down by alterna-
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HAND-BOOK OF ALABAMA.
tions of heat and cold, they cover the ground with angular fragments, that in process of time are worn into the rounded pebbles that are so widely distributed over the rest of the State. The conclusion seems unavoidable, that the southeast- ern part of these crystalline rocks is older, or has been longer subjected to sub-ærial decay, than the parts further to the northwest.
The Crystalline Schists, or Archæan Rocks, have, in other parts of the United States, been arranged in two series, called Huronian and Laurentian, the latter being the older of the two and presumably the oldest rocks of which we have any knowl- edge. By some geologists these are considered as older than . any of the stratified fossiliferous rocks, while by others they, as well as the Huronian, are thought to be the altered and crystallized sediments of the Cambrian, Silurian, and perhaps later ages.
Without attempting to decide any of these matters for Alabama, we may again recur to the fact that the rocks near the eastern border of this region appear to be much older, or at least to have been very much longer exposed to the disinte- grating action of the atmosphere than those towards the west, or northwest, and it is almost certain that some of the rocks along this northwestern border are nothing more than the Choccolocco or Montevallo shales and the Weisner quartzite metamorphosed, or changed to crystalline schists.
.
Materials of Economic Value .- The granites and gneisses above named are used in some slight degree as building stones, and deserve more attention than they have received from quar- rymen. The same rocks, especially the granites, which are found chiefly along a belt running northeast from near Brad- ford, in Coosa county, are also largely used for the manufacture of millstones.
Marbles and Dolomites .- Near Talladega and Sylacauga occurs a bed of good crystalline marble that has been worked at a number of localities, and has yielded some fine material. In Lee county, near Opelika, there is a crystalline dolomite which is white, and would make a fine ornamental and build- ing stone, hardly to be distinguished from marble. This sub- stanee has for years supplied the Chewacla lime works and gives a lime of very superior quality.
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GEOLOGY OF THE STATE.
Soapstone or Steatite .- This rock is found in several parallel belts running northeastward from the Coosa river. It has been quarried in Chambers county for the manufacture of mon- uments, headstones, and the like, and for furnishing fire-proof lining to the Chewacla lime kilns, for which purpose it answers admirably.
Porcelain Clay .- The decomposition of the feldspar of granites, and other rocks, gives rise to the formation of clays which, when not mixed with other substances, are suitable for the manufacture of porcelain and fine ware. The best known occurrences of this clay are near Louina, Randolph county, and near Socapatoy, in Coosa, and Notasulga, in Macon.
Glass. Sand .- There are some friable white sandstones in Chilton county that crumble readily between the fingers, which, with proper selection, would furnish pure silica fit for the manufacture of glass.
Asbestos .- This substance occurs at various localities in Coosa, Tallapoosa and Chambers counties, near the deposits of corundum, below to be noticed. Nothing has yet been done toward the development of these beds, and it is not known that they exist in sufficient quantity to be of value.
Mica .- In some of the mica schists and gneisses, especially in the northwestern part of the region of the crystalline rocks there are veins filled with large crystallized masses of quartz, feldspar and mica, and it is these masses of mica that furnish the mineral in quantity. We have as yet no regular works among the mica veins, but enough ha's been done to show that mica plates of very good size can be gotten in many places. The ancient excavations that are found along the belt of coun- try from Chilton to Cleburne county, mark the spots where mica has been mined in the past, and the experience of the mica miners in North Carolina goes to show that the best inica is usually to be found by reopening these old mines.
Corundum-Ilas been found in considerable quantity near Dudleyville, in Tallapoosa county, and also near Bradford, in Coosa county. That in Coosa is usually very much altered, and it would be probably difficult to use it because of the alteration which it has suffered. The Tallapoosa corundum is, so far as yet known, in fragments, the solid bed having never been uncovered.
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892
ILAND-BOOK OF ALABAMA.
Zircon-Has been found near Bradford, in Coosa county, nearly transparent and well crystallized. The best specimens of this mineral are sometimes used as gems.
Graphite-Is widely disseminated in small quantities in many of the crystalline rocks, sometimes impregnating alum- inous slates to such an extent as to render them suitable for lubricating purposes. Some very fine seams of graphite have recently been found near Enitachopka, in Clay county, and it is probable that it will be found in other counties in sufficient quantity and of sufficient purity to be valuable.
Gold .-- Most of the gravels and sands of this region have in the past been profitably worked for gold. Arbacoochee, ' Chulifinnee, Pinetucky and Goldville are well known localities. For many years, however, this kind of work has ceased, and so has the working up of the quartz in stamp mills. There is reason for thinking that, with the new processes for the extraction of gold from low grade ores, many of our ores can yet be worked with profit. The geological survey is at present engaged in the investigation of these processes in connection with the Alabama gold ores .*
Copper .- The history of the copper mining in Alabama is similar to that of gold. Some years ago a good deal of money was invested in a copper mine in Cleburne county, and the . . works flourished until the rich surface ore was used up. The mundic or main body of the vein, containing only a small percentage of copper, could not be profitably smelted, on account of distance from lines of transportation, etc., and work there has been suspended for a number of years. Cop- per is known . to occur in very many localities in this region, but the mine above named is the only one where any system- atic work has been done of late years.
Manganese .- Although manganese is very extensively dis- tributed through this region, no large deposits of it have yet been found.
Iron Ores .- The important iron ore of the crystalline rocks is magnetite, and it has been found in most of the counties of this region of the State, but not, so far, in great quantity, although search has been very persistently made for it. Good
. A bulletin (No. 4, on the lower portion of the gold region has been published since the above was in manuscript.
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393
GEOLOGY OF THE STATE.
sized fragments of magnetite, indicating a bed of considerable thickness, have been found in Cleburne, Clay, Randolph, Cham- bers and Tallapoosa counties. In Talladega county there is a sandstone impregnated with magnetite to such a degree as almost to make it a workable ore of iron.
Hematite or Specular Ore-Is also common in many of the rocks of this region, but no large beds of it are yet known ..
Limonite --- Is also abundant in many cases as "gossan," i. e., the result of the decomposition of pyritous ores. Some of the limonite, however, which was once used in the old Catalan forges appears to be of a different kind. In all the region where the rocks are partly or entirely composed of hornbleude, these iron ores of various kinds are more or less abundant.
Pyrite .-- Extensive beds of iron pyrite or pyrites are known in Clay county, of this State, but have not yet been worked. Most of the copper ore of the State is pyrite with a certain percentage of copper. In concentrating these ores, the sul- phur of the pyrite is allowed to go to waste. In the English works, this & utilized in manufacturing sulphurie acid, the profit upon which alone pays well, whilst the copper and also the iron are pure gain. With capital sufficient to provide for manufacturing sulphuric acid, copper works will be made to pay a much greater profit than they do now. In view of the recent discoveries of phosphate in Florida, it might be well to take into consideration the possibilities of our pyrite beds as furnishing material for the manufacture of sulphuric acid, . used in the production of super-phosphates.
Rutile or Titanic Acid-Is a mineral of very general occurrence. Good speennens have come from Coosa and Chil- ton counties. Its uses in the arts are limited, but its value as a cabinet specimen, well crystallized, will command a ready sale.
Tantalite .- This rare mineral has been found for the first time in this State, in Coosa county, near Rockford. The anal- ysis of it, by J. Lawrence Smith, of Louisville, Kentucky, was published in the first edition of this book.
Beryl .- This mineral has been obtained from Coosa county in crystals, which have yielded very handsome gems when eut.
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394
HAND-BOOK OF ALABAMA.
PALEOZOIC FORMATIONS.
Classification and Lithological Characters. - The geolog- ical formations of the above list, from Carboniferous to the Cambrian inclusive, have been grouped together in one divis- ion, called Puleozoic (ancient life), in allusion to the want of resemblance to the present existing forms of the animal and plant remains contained in them.
In the following account of the distinguishing characters of the rocks of each of the great groups of formations-Com- brian, Silurian, Deronian and Carboniferous, which constitute the Paleozoic-we shall follow pretty closely what has already been printed in the report on the Cahaba coal fields.
The Cambrian .- The rocks of this formation are con- glomerates, sandstones and shales in the Coosa valley region, and shales and shaly limestone in the valleys further west, the maximum thickness of the whole being put at 10,000 feet ; but this great thickness is seen only in the' eastern part of the Coosa valley. In the other valleys the thickness is less than half of the above.
The subdivisions of the Cambrian which we recognize in 'Alabama are as follows : The Coosa shales, the Choccolocco or Montevallo shales, and, interbedded with the last named, the Weisner quartzite. These subdivisions are based rather upon · the lithological characters than upon the chronological succes- sion, which cannot at this time be given with certainty, for the calcareous shales, which we class with the Coosa, have recently been found to contain upper Cambrian fossils, while some of the shales of the Montevallo type have yielded lower Cambrian fossils. On the other hand, some of the Montevallo type of shales may be seen in places immediately underlying the strata of the Knox dolomite, while in other places the Coosa or flatwoods type of shale has apparently the same position. It is very probable that the difference in the composition of the Cambrian shales-i. e., whether calcareous or sandy-is due to the geographical and other conditions existing during their time of deposition, and that both kinds were formed contemporaneously-a part near the shore line : a part further
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395
GEOLOGY OF THE STATE.
out to sea. In certain parts of the Coosa valley, where both types of shales occur together, the calcareous shales of the Coosa type appear very generally to underlie those of the siliceous or Montevallo type.
Coosa Shales .- In the valleys above mentioned, the rocks of this division are thin bedded limestone, with elay seams between-usually very greatly contorted and tilted at high angles. Where these rocks come to the surface, there results from their decomposition a very stiff calcareous clay soil. These lands being very level, and hence very badly drained, are not much cultivated in Alabama, and are generally known as " flatwoods." The shaly limestones that give rise to these flatwoods we have called Coosa shales.
Monterallo Shakes .- In the Coosa valley, and especially in its eastern parts. and in the southwestern part of the Cahaba valley, towards Helena and Montevallo, we find a considerable thickness of siliceous or sandy shales of great variety of colors, such as olive green. chocolate, yellowish, etc. The original material was a calcareous matter has mostly been pretty thoroughly leached out, and only the more siliceous parts left. These shales crumble up in places to small fragments about the size and shape of shoe pegs. Sometimes they are more tough, and, especially towards the east, assume gradually the characters of the semi-crystalline rocks, and it is capable of demonstration that some of the partly crystalline slates of the eastern part of the Coosa valley are only the changed or meta- morphosed representatives of this division, which has been called the Monterallo or Choccolocco shules, from the character- istic occurrences in those localities. In the upper part of the Montevallo shales we find beds of blue limestone and gray dolomite, which it is often difficult to distinguish from the similar rocks occurring in the next overlying the formation. In fact, the line between the shales and the Knox dolomite is, so far as Alabama is concerned, rather an arbitrary one.
Weisner Quartzite .- In the shales just described, and most commonly in their lower parts, are found in the eastern part of the Coosa valley great beds of quartzite and conglomerate, many hundred feet in thickness, but often of very limited ex- tent geographically. The quartzite always forms high and rugged mountains, sometimes stretching for miles in an un-
396
HAND-BOOK OF ALABAMA.
broken range, but as often forming detached and isolated peaks rising suddenly out of the plains and as suddenly sinking down to the same level. The "mountain " near Columbiana, the Kahatchee hills, Alpine mountain, Mount Parnassus, at Talla- dega, Coldwater mountain and Blue mountain, near Anniston, the Ladiga mountain, above Jacksonville, and the Weisner mountain, east of Jacksonville, are instances of occurrences of this quartzite. The Weisner mountain has been most studied, and its stratigraphical relation to the Coosa shales, and to the Choccolocco shales, most clearly made out, for which reason we have used the term - Weisner quartzite - to designate this member of our Cambrian, which occurs interpolated in the shales, as local masses of lentienlar shape, often of very great thickness.
Prof. Safford, of Tennessee, has given the name Chilhowee to similar great masses of sandstone and quartzite occurring in that State, apparently below the shales above named. Prof. Safford places these sandstones always below the shales, but this does not seem to be their position in Alabama, as the masses of sandstone oceur at different horizons, interbedded with the shales. For this reason we have not used Prof. Saf- ford's name to designate the rock. Similarly, it appears neces- sary to adopt a distinct name for the thin-bedded limestones with clay seams, of our " flatwoods," since they play a very subordinate part, if they occur at all in Tennessee. In general the Choccolocco and Coosa shales, as above defined, are partly, at least, the equivalents of the Knox sandstone and shale of Tennessee, but apparent important differences in the strati- graphy of these beds, in the two States, make it impossible as yet to correlate them strictly, hence our adoption, provisionally at least, of different names.
The Silurian .- We have not yet, in Alabama, found it practicable to arrange our Silurian formation in more than three principal divisions, which, beginning at the lowest, and coming upward, are as follows: Knox dolomite, Trenton or Pelham limestone, and Red Mountain or Clinton.
Knox Dolomite .- This name has been given by Dr. Safford to a series of rocks occurring in the vicinity of Knoxville, Ten- nessee, and inasmuch as the rocks of this horizon in Alabama are identical with those described by him, we have retained
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GEOLOGY OF THE STATE.
the name in the Alabama survey. This is one of the most im- portant and widely spread of our older geological formations, and its characteristic rocks are magnesian limestones, or dolo- mites, sometimes quite pure, but more often impregnated with siliceous matter. This siliceous matter is sometimes found as a sandy impurity in some of the dolomites, upon the weather- ing of which it becomes quite prominent. For this reason many of the dolomite beds of the lower part of the Knox dolo- mite, when exposed to the weather. show a rough and sandy surface, marked by shallow cracks running in every direction, as if the rock had been hacked or gashed by some cutting in- strument. These purer and sandy dolomites, together with some beds of tolerably pure blue limestone, occur near the base of the Knox dolomite, and are very closely related to the beds of the shale division already described .* On the other hand, the siliceous matter in the upper part of the formation is usu- ally found in masses of chert, of concretionary origin, impreg- nating the dolomite, and on the breaking down of these rocks, under the action of the weather, the calcareous parts are leached out, while the siliceous parts usually remain in the form of angular, flinty gravel, which forms the very character- istic ridges of Knox dolomite. The weathering of the lime- stones and the dolomites, near the base of this division, has given rise to the formation of gently undulating terranes, with a deep red-colored sandy loam soil, of more than average fer- tility, which is the base of the best farming lands in all these valleys. The red lands about Elyton. and in parts of Birming- ham, and in the Alexandria valley, across the Coosa, are good examples. In the upper part of the dolomite the cherty, or siliccous matter, is more abundant as a surface material than the calcareous, and the country is broken or ridgy, rather than undulating. Some of these flint ridges extend for long dis- tances unbroken. Good examples are the ridges of the north and south highlands about Birmingham. In fact, this angular, cherty gravel is found upon all the lands made by the Knox dolomite, but is much more abundant and characteristic in the upper part. The Knox dolomite contains very few fossils, and these belong to the lower Silurian horizon of the paleontolo-
. Recent investigation appears to show that part of these limestone beds belong, in all probability, to the Cambrian formation.
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HAND-BOOK OF ALABAMA.
gists, but we have in the chert itself a characteristic by which we can, as a rule, distinguish it from the chert of other forma- tions - that is, in most of it are small, angular cavities of clearly defined shape, which are usually thought to mark the place once occupied by rhombohedral crystals of dolomite, sub- sequently dissolved out. Prof. Safford was the first to call attention to this mark, which we have found to be an extremely nseful one .* The Knox dolomite, as well as the upper part of the underlying formation, seems to have held originally much ferruginous as well as siliceous matter, and throughout the region formed both by the dolomite and the upper part of the shale, occur the beds of the brown iron ore, or limonite, which play so important a part in the economic history of all this region. The iron ore seems to have been derived from these older rocks. As instances of the occurrence of limonite banks connected with the dolomite and shale, I may mention the Ed- wards ore bank, near Woodstock, the mines at Greely and Gæthite, in Jones valley, and the great beds at Shelby, over the Coosa. The great bulk of the brown iron ores of Alabama is from this horizon.
At the top of the Knox dolomite, and belonging perhaps to the next succeeding division, there is rather a peculiar rock occurring at intervals along Jones valley and elsewhere. It is a breccia, made up of angular fragments, chiefly of the chert of the Knox dolomite, cemented together into a rock which is a good many feet in thickness. This rock, being made of frag- ments of the Knox dolomite, is, of course, younger, though, on account of its materials, we have usually classed it along with. the Knox dolomite. It is seen in the greatest volume in the Salem hills, southwest of Bessemer, but occurs upon the flint ridge forming the north highlands at many points, e. g., Bir- mingham and Gate City, and also west of Springville. It has been called the Birmingham breccia by Mr. Russell of the United States survey, and Salem breccia by us in the State survey. It is of interest as showing that a period of disturb- ance intervened between the time of the formation of the Knox dolomite and that of the Trenton limestone.
Trenton or Pelham Limestone .- As its name implies, this
· Similar angular cavities have recently been observed in the dust of other form- ations, so that this is not an altogether characteristic mark of the dolomite.
399
GEOLOGY OF THE STATE.
division is mostly calcareous. It may be perhaps, as'a maxi- mum, 800 feet in thickness, and varies considerably in quality, the lower part being usually impure and shaly, while the upper part is mostly a pure limestone, often used for the pur- pose of making lime and as a flux in the furnaces. The lower part usually holds great numbers of shells of Maclured nutgna, a characteristic fossil of the Chazy limestone of the New York geologists. The purer limestone above is also quite full of fossils, which, as a group, are those of the Trenton limestone of New York.
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