Cochliodnii eontnrtns (fig. 547) ; among Hybodonts (or sharks
with regular teeth, the teeth with obtuse or rounded edges) there
is the CladoduH marginatm. Fig. 557 represents a small spe-
cimen of one of the great fish-spines of this period, called Cte-
nacaiithus major by Agassiz. One specimen has a length of
fourteen and a half inches, and was probably eighteen inches in
the living Cestvaciout. The old fishes, as Agassiz observes, must
have had gigantic dimensions, if we may judge from the size
of the spines.
Pbillii).->ia semi-
uifera.
Fig.
OiU.
Part of a spine of Ctenacantbus major
Another spine, Oracantlius Milleri, Agassiz, is nine and a half inches long and
three inches wide at base, and yet it has lost some inches at its extremities. These
320
PALEOZOIC TIME ā CARBONIFEROUS AGE.
specimens, and numerous other remains of fishes, are found in a fish-bone bed in
the mountain limestone at Bristol, England, and also in the same rock at Armagh,
Ireland. The British and European species, although numerous and often large,
do not exceed in either respect those which have been already found in con-
nection with the Subcarboniferous beds of the United States.
DISTURBANCES PRECEDING THE CARBONIFEROUS
PERIOD.
It was remarked on page 305 that the Devonian beds are very
generally conformable with the Subcarboniferous, and therefore
afford in but few places indications of uplifts before the Subcar-
boniferous period and its formations began. There is the same con-
formability for the most part between the Carboniferous and Sub-
carboniferous ; yet the examples of the absence of it are more
numerous, and cover some wide regions. Through the investiga-
tions of Norwood, Daniels, Foster, and Hall, it is now known that
the Coal measures of Iowa, Missouri, and Illinois rest unconform-
ably upon the strata beneath, and Hall observes " that this is so
whether these strata be the Subcarboniferous, Devonian, Upper
Silurian, or Lower Silurian." The want of conformability is very
distinct in certain parts, and but slight in others ; and in some cases
it is apparent only in the marks of extensive surface-denudation
which took place at some time preceding the Coal period.
In the annexed sections, the coal beds rest on tilted Silurian
strata. Fig. 558 is a section in northern Illinois. The Coal mea-
sures here overlie the Lower Silurian ; a, calciferous sandrock ; 6,
Fig. 558.
St. Peter's sandstone (Chazy?) ; c, Trenton and Galena limestone ; d,
Coal measures. (J. W. Foster.) Fig. 558 A was taken at Port Biron,
Rock Island co., Illinois, and shows the Coal measures A, resting
'unconformably on the Niagara lime-
stone B. (Worthen.) In this region, ^'^^- ^^^ ^ā¢
the strike of the uplift is parallel to (^^^^^
the course of the Rocky Mountains, yXyy/A'/l^'^y^ZZ/^X,
or nearly northwest. A portion of
these uplifts directly preceded the Coal period. But others may be
of earlier date ; for where the tilted rocks underneath are Silu-
rian or Devonian instead of Subcarboniferous, it is not yet certain
CAllBONIFEUOUS PEUIOD. 321
at what epoch the disturbance took place; and it may have long
preceded the Carboniferous age. More investigation is required to
lix the date.
No example of Carboniferous beds lying unconformably on tilted
Subcarboniferous beds has yet been observed in Pennsylvania, Vir-
ginia, or New Brunswick.
In Great Britain, Russia, and the most of Europe, the Carbonife-
rous and Subcarboniferous beds, when occurring together, are con-
formable. But in central and southern France, as Murchison says,
the two are always \inconformahle. In Bavaria, also, at Hof, the Sub-
carboniferous limestones and Devonian follow one another regularly,
though inclined together at a large angle; while the coal fields of
Bohemia lie in horizontal strata over their tilted edges.
'n^
2. CARBONIFEROUS PERIOD (14).
Epochs. ā 1. Epoch of the Millstone grit; 2. Epoch of the Coal
measures.
1. EPOCH OF THE MILLSTONE GRIT (14 a).
I. Rocks : kinds and distribution.
The Carboniferous period opened with a marked change over the
continent. The Subcarboniferous limestones and shales which
were formed upon the submerged land became covered with ex-
tensive gravel or pebble beds, or deposits of sand ; the beds of that
epoch, hardened into a gritty rock, make up the millstone grit and
sandstone which underlie the Coal measures.
Similar comjlomerates and sandstones were formed afterwards in
the course of the Coal measures ; but this rock is jDrominent for its
extent, and for marking the commencement of the Coal era.
The Coal period in Britain has in general the same kind of intro-
duction : the term Millstone grit applied to the rock comes to us
from England.
This Millstone grit extends over parts of some of the southern
counties of New York, with a thickness of 25 to 00 feet ; and, owing
to the regularity of the joints, it stands out in huge blocks, walls,
and square structures, that have suggested such names as " Rock
^'ity" and "Ruined City" (Cattaraugus and Allegany cos.). It
occurs through all the Coal areas of Pennsylvania, both the eastern
and western ; it is from 1000 to 1500 feet thick about the centre
of the anthracite region, and diminishes rapidly to the westward.
It stretches southwest ward throuiili Yiririnia to Alabama.
22
322 PALEOZOIC TIME ā CARBONIFEROUS AGE.
West of the Appalachian region, the rock is in part a pebbly
sandstone, but often only a fine-grained, arenaceous rock ; and from
some portions of the Mississippi basin it is absent.
Thin beds of coal occur in these conglomerates, and in certain
localities they are of workable extent.
(a.) Interior Continental basin. ā In Ohio, Indiana, and Illinois, there are 40 to
100 feet of pebbly sandstone ; in eastern Kentucky, a sandstone, which is 50
feet thick on the Ohio and 250 on the borders of Tennessee ; in western Ken-
tucky, a conglomerate, called the Caseyville conglomerate. It is probable that
these conglomerates and sandstones, referred to the beginning of the Coal mea-
sures, belong to this initial epoch of the period. In Arkansas, the novacuiiti
used extensively for hones, and also gi'eat numbers of quartz crystals, occur
in beds referred to this epoch.
{h.) Apiialacliian region. ā The grit in Pennsylvania is mostly a whitish sili-
ceous conglomerate, with some sandstone layers and a few thin beds of carbona-
ceous shale : it overlies the Subcarboniferous shale or sandstone. At Tamaqua,
the thickness is 1400 feet; at Pottsville, 1000 feet; in the Wilkesbarre region,
200 to 300 feet; at Towanda, Blossburg, etc., where it caps the mountains, it is
50 to 100 feet thick. (H. D. Rogers.)
In Virginia, the thickness is in places nearly 1000 feet: the rock is mainly a
sandstone, but contains heavy beds of conglomerate. The conglomerate of the
Subcarboniferous, in a similar manner, becomes an arenaceous rock in Virginia.
In Alabama, the rock is a quartzose grit of great thickness : it is used for mill-
stones.
(c.) Eastern border region. ā In the Nova Scotia and New Brunswick Coal region.
a millstone grit has been observed in the Carboniferous district of northern
Inverness and Victoria ; but only sandstones overlying gypsiferous rocks in
Pictou CO., and shale? iind sandstones at the Joggins.
2. EPOCH OF THE COAL MEASURES {Ub).
I. Distribution of the Coal Areas.
The Carboniferous areas of North America have been pointed out
on p. 305. The regions corresponding to the Coal period (black
areas on the map, p. 133) are ā
1. The great Appalachian coal field, covering parts of Pennsylvania.
Ohio, Virginia, eastern Kentucky, eastern Tennessee, and Alabama.
The workable area is estimated at G0,000 square miles. The whole
thickness of the formation is 2500 or .3000 feet: aggregate thick-
ness of the included coal beds, over 120 feet in the Pottsville and
Tamaqua valley, about 62 feet near Wilkesbarre, 25^- feet at Pitts-
burg. The area is partly broken up into patches in Pennsylvania,
as shown in the following map. In the centre of the State, between
Pottsville and Wyoming, are the famous anthracite beds, divided
CARBONIFEROUS PKRIOI).
32a
into many distinct patches ; and in the western part commences
the great bituminous coal tield which spreads into Ohio and stretches
on south to Alabama.
2. The IKinois and Missouri., covering a very considerable part oi"
Illinois, ])art ol" Indiana and Kentucky, and, west of the Missis-
sij)pi, portions of Iowa, Missouri, Kansas, and Arkansas. p]sti-
mated area, 60,000 square miles. Whole thickness of the formation,
in Missouri, GOO to 1000 feet ; in western Kentucky, nearly 3300 feet,
ā with about 70 feet for the aggregate thickness of the coal beds.
CO
3. The Michigan, situated about the centre of the peninsula.
Estimated area, about 5000 square miles. Whole thickness of the
o24 PALEOZOIC TIME ā CARBONIFEROUS AGE.
formation, 123 feet ; rests upon a sandstone, probably of the Mill-
stone grit epoch, which is 105 feet thick.
4. The Texas, covering several of the northern and northwestern
counties.
5. The Rhode Island, lying between Providence and Worcester
in Massachusetts, and opened at Cumberland north of Providence,
at Portsmouth 23 miles south, and also showing thin seams at
Newport and elsewhere ; in Massachusetts, outcropping at Mans-
field 15 miles northeast of Providence, at Wrentham 5 miles
from Mansfield, and at Worcester. Estimated area, 1000 square
miles.
6. The New Brunswick, covering part of New Brunswick, Nova
Scotia, Prince Edward's Island, and Newfoundland. Estimated
area, 18,000 square miles. Whole thickness of the formation at the
Joggins, including the beds of the Millstone-grit epoch, 14,570
feet : the number of included coal beds is 76, some of them being
very thin, and the aggregate thickness 45 feet. (Logan.) These
coal beds are situated in a part of the Coal measures, 2819 feet
thick, near the middle of the series. At Pictou there are six beds
of coal, with an aggregate thickness of 80 feet, (Dawson.)
The total number of square miles of all the productive coal fields
of the United States is 125,000.
Besides the above, there is the Arctic Coal region, which has been
observed on Melville and Bathurst Islands, Banks Land, etc., and
the Rocky Mountains, both of which are yet unexplored.
Limestones of the Carboniferous period ā formerly supposed to be Subcarboni-
forous ā have a wide distribution over the summit and both the eastern and
western slopes of the mountains. This limestone has been observed at the
Black Hills in Dakota, and the Laramie Range; about the head-waters of the
Missouri; at the South Pass of the Rocky Mountains; in the ranges south of
Pike's Peak, and east and west of Santa Fe, New Mexico; in the great basin
()f the Colorado; and it probably underlies to a considerable extent the Meso-
zoic rocks of the Rocky Mountain slopes west of the Mississippi.
II. Rocks.
1. Kinds of rocks, and stratification. ā The Coal measures include stra-
tified rocks of all kinds, ā sandstones, conglomerates, shales, shaly
sandstones, limestones ; and the limestones are generally impure,
or magnesian. There is the same wide diversity that occurs in the
Devonian, with more numerous and rapid transitions than were
common in that age. Moreover, the rocks differ much in different
regions.
The Coal beds are additional layers in the series, interstratified
CARBONIFEROUS PERIOD. 325
with the shales, sandstones, conglomerates, and limestones. But
they are thin, compared with the accumulation of rock-strata.
The Coal measures contain, generally, 50 feet or more of beds of
rock to one foot of coal.
Iron-ore beds also occur, making other thin layers in. the series,
and rendering the Coal regions the best iron regions of the globe.
The following section is an example of the alternations (beginning below) : ā
1. Sandstone and conglomerate beds 120 feet.
2. COAL 6 "
3. Fine-grained shuly sandstone 50 "
4. Siliceous iron-ore H "
5. Argillaceous sandstone 75 "
6. COAL, upper 4 feet shale, Avith fossil plants, and below a thin
clayey layer 7 "
7. Sandstone 80 "
8. Iron-Ore 1 "
9. Argillaceous shale 80 "
10. Limestone (oolitic), containing /'/ā¢otZĀ»cf(', Criuoidn, etc 11 "
11. /?-oH-0/-e, with many fossil shells 3 "
12. Coarse sandstone, containing trunks of trees 25 "
13. COAL, lying on 1 foot slaty shale with fossil plants 5 "
14. Coarse sandstone 12 "
The alternations are thus various, and may follow any order.
The shales, sandstones, conglomerates, and limestones resemble
the corresponding rocks of other periods, and they are distinguished
as belonging to the Coal measures only ly the fossil plants or animal relics
they may contaiti. Disastrous errors are often made when this rule is
not regarded.
The beds, even when thick, whether of coal or of any of the
rocks mentioned, have in some districts a limited lateral extent;
yet in this respect the Coal measures differ little from earlier forma-
tions. Some of the larger beds of coal are supposed to spread con-
tinuously over many thousand square miles of area.
In connection with the Coal measures of Rhode Island there are extensive
beds of quartzose conglomerate, which outcrop at Newport and elsewhere, and
form a bold feature in the landscape at " Purgatory," 2h miles east of Newport.
They occur also in Massachusetts, between this region and Boston, showing
well about Roxbury. The exact position of the beds in the series is not
known, as the rocks have undergone great disturbance, and in some places so
much metamorphism that the cementing material is a talcose schist. At Taun-
ton, Mass., its pebbles have occasionally been found to contain Lingula; of the
Potsdam sandstone {Lingula 2irima), proving that they are pebbles of this Pri-
mordial rock ; but whence derived is unknown.
326
PALEOZOIC TIME ā CARBONIFEROUS AGE.
Besides the rocks mentioned, a buhrstone occurs in beds several
feet thick, in Ohio. It is a cellular, flinty, siliceous rock, valued
highly for millstones.
The limestones are more extensive in the Coal measures of the
Mississippi basin than in those of Pennsylvania and Virginia ;
while, on the contrary, conglomerates are much less common in
the West. This accords with the fact, learned from the earlier
ages, that the Appalachian region is noted for its conglomerates
and sandstones, and the Interior basin for limestones.
In Wayne co., in western Pennsylvania, there are 80 feet of limestone in 350
feet of Coal measures; and near Wheeling, on the Ohio, twice this thickness of
limestone. In Missouri, there are 150 feet or more of the former to 650 of the
latter. In the lower 150 feet of the Missouri section there are, however, but
8 feet of limestone, and in 900 feet of the Lower Carboniferous in western Ken-
tucky, only 10 feet. The limestones included among the strata appear often to
have a limited lateral range, instead of the uniformity over extended areas
common in earlier periods.
The rock underlying a coal bed may be of either of the kinds
mentioned; but usually it is a clayey layer (or bed of finer clay)
which is called the under-day. This under-clay generally contains
fossil i)lants, and especially the roots of Carboniferous plants called
Stigmarice, and it is regarded (as first shown by Logan) as the old
dirt-bed in which the plants grew that commenced to form the
coal bed. In some cases trunks of trees rise from it, penetrating
the coal layer and rock above it.
The Nova Scotia Coal region abounds in erect trunks, stand-
ing on their old dirt-beds, as illustrated in fig. 560 (by Dawson).
Fig. 560.
Section of Coal Measures at the Joggins, Nova Scotia (with erect stumps in the sandstone,
and rootlets in the uuder-clays).
Each of the 76 coal seams at the Joggins has its darker clayey
layer, or dirt-bed, beneath. In 15 of them there is onlv a trace of
CARBONIFEROUS PERIOD. 327
coal ; but these, as well as the rest, contain remains of roots [Stig-
niarid'), and often sujiport still the old stumps. (Dawson.)
The rock caiiping a coal bed may be of any kind, for the rocks
are the result of whatever circumstances succeeded ; but it is
common to find great numbers of fossil plants and fragments of
trees in the first stratum.
The shaly beds often contain the ancient ferns spread out between
the layers with all the perfection they would have in an herba-
rium, and so abundantly that, however thin the shale be split, it
opens to view new impressions of plants. In the sandstone layers,
broken trunks of trees sometimes lie scattered through the beds.
Some of the logs in the Ohio Coal measures, described by Dr. Hil-
dreth, are 50 or 60 feet lon'j: and 3 feet in diameter.
The thickness of the coal beds at times hardly exceeds that of
paper, and again is from 30 to 40 feet. The beds also vary in purity,
from coal with but 1 per cent, of earthy matter, to dark-colored
shales with only a trace of coal. The thickness is seldom over 8
feet, and the impurities ordinarily constitute from 7 to 15 per cent.
The Pittsburg seam, at Pittsburg, Pa., is 8 feet thick. It borders
the Monongahela for a long distance, the black horizontal band
being a conspicuous object in the high shores. It may be traced,
according to Kogers, into Virginia and Ohio over an area at least
225 miles by 100 ; and even into Kentucky, according to Lesquereux.
But it varies in thickness, being 12 to 14 feet> in the Cumberland
V)asin, 6 feet at Wheeling, 5 at Athens, Ohio, and on the Great
Kanawha ; farther south, at the Guyandotte, 2 to 3 feet.
The "Mammoth Vein," as it is called, which is exposed to view
at Wilkesbarre, Pa., is 29 J feet thick. It is nearly pure through-
out, although there are some black shaly layers 1 to 12 inches
thick. The same great bed is worked at Carbondale, Beaver Mea-
dows, Mauch Chunk, Tamaqua, Minersville, Shamokin, etc.
At Pictou, in Nova Scotia, one of the coal beds has the extra-
ordinary thickness of 372^ feet, and a second 22]- feet.
2. Structure of the Coal. ā A bed of coal, even when purest, consists
of distinct layers. The layers are not usually separable, unless the
coal is quite impure from the presence of clay ; but they are
still distinct in alternating shades of black, and may be seen in
almost any hand specimen of the hardest anthracite, forming a
delicate, though faint, banding of the coal.
In much of the bituminous coal of the Mississippi basin a cross-
fracture shows it to be made up of alternate laminae of black,
shining, compact bituminous coal, and a soft, pulverulent car-
bonaceous matter, much like common charcoal.
328
PALEOZOIC TIME ā CARBONIFEROUS AGE.
The coal itself varies much in character. In some regions, as in
the Schuylkill (at Pottsville, Mauch Chunk, etc.) and Wilkesbarre
coal fields, at Peak Mountain, in Virginia, and in Rhode Island,
it is of the kind called Anthracite (see page 68), which is non-bitu-
minous, and burns with very little bluish flame. At Pittsburg, and
through nearly all of the Appalachian coal field, and in the other
coal areas of North America, it is Bituminous coal, which burns
readily with a bright-yellow flame.
The bituminous coal is either the ordinary brittle kind, break-
ing into lustrous angular pieces, or the compact Cannel coal, dis-
tinguished by its firmness, slight lustre, conchoidal fracture, and
the absence of any laminated structure. Cannel coal often gra-
duates into ordinary bituminous coal.
In many places there are vegetable remains in the coal itself,
such as impressions of the stems of trees, or leaves, or charcoal-
like fragments which in texture resemble charcoal from modern
wood. Fig. 561 a represents a specimen of this kind from Tusca-
loosa, Ala., as figured by Bunbury : it has a fibrous appearance to
the naked eye, but under a pocket-lens shows rectangular meshes
over the whole (fig. 561 b), like the structure of the leaves of some
water-plants.
Even the solid anthracite has been made to divulge its vegetable
tissues. On examining a piece partly burnt. Professor Bailey
Fig. :>CA.
Fig. 562.
found tTiat it was made up of carbonized vegetable fibres. The
annexed figures 562 a, b, c, are from his paper on this subject. Ho
CARlJONirEROUS 1>ERI01>. 329
selected specimens which were imperfectly burnt (like fig. 5G2 a),
and examined the surface just on the borders of the black portion.
Fig. 502 6 represents a number of ducts thus brouglit to light, as
they appeared when moderately magnified, and fig. 502 c two of the
ducts more enlarged ; the black lines being the coal that remained
after the partial burning, and the light spaces silica. The ducts
were ^^^ih of a millimetre (about four-thousandths of an inch)
broad. No stronger evidence could be had of the vegetable origin
of anthracite coal.
Pj/ritcs (sulphuret of iron, page 04) is sometimes disseminated
through coal beds in nodules or seams, to the serious injury of the
coal. Such coal crumbles down on exposure to the air, and gives
forth sulphur fumes when burnt. Even the best of mineral coal
contains traces of i)yrites ; and to this is oAving the sulphur smell
ordinarily perceived from coal fires.
3. Irou-orcs. ā The iron-ore beds arc usually from a few inches to 3 or 4 feet in
thickness. They contain the ore in concretionary masses or plates of a stony
aspect. The most common but not most A'aluable kind has a grayish-blue
and drab color on a fresh surface of fracture, and differs from limestone in being
unusually heavy : this ore, called clay-irovstonc, is an impure spathic iron or
chalijhite (p. 63). Another variety of iron-siotie is an impure hematite (p. 65),
affording a red powder. Still another kind is an impure liinonitc (p. 65), having
a reddish-brown or ycllowish-bi'own color and affording a brownish-yellow pow-
der : beds of this variety are few, but widely extended, thick, and valuable.
4. U})2ier and Lower Coal Measures. ā The Coal measures are sometimes divided
into the Upper and Lower Coal measures. The most convenient division is
above the "Mammoth bed" of Pennsylvania, ā as there is a marked change in
the flora from this point. It has been proposed to make the Mahoning sand-
stone the dividing bed, above the Upper Freeport coal bed, which is the third
above the so-called Mammoth bed in the Pennsylvania series. Another great
sandstone stratum, called the Anvil Rock, occurs in Kentucky, above the twelfth
Coal bed in the Kentucky series,- and this has also been made a dividing
stratum in the measures. There is nothing in the fossils that renders the sub-
division at these places of geological importance. (Lesquereux.)
The great Anthracite region of Pennsylvania is largely Lower Carboniferous.
The Upper Carboniferous is present there (at Pottsville, Shamokin, and Wilkes-
barre) up to the top of the Pittsburg group (Lesley) ; but the rest does not extend
so far eastward. The greatest development of the lower coal was in Pennsyl-
vania; and of the upper, in the States farther west. Tliehighest beds in the series
appear to occur west of the Mississippi, in K:;nsas, where they nier:rc into the
Permian. There are, however, according to McKinley, 3000 feet of barren Coal
measures above the level of the Pittsburg coal, in the southwest corner of Penn-
sylvania and the adjoining part of Virginia, and it is not certain how far
upward they may reach in the series.
5. EqnivaJcucij of the Ajipalachi'an and Iflhiois Coal Jifcafnires. ā There is great
difficulty in arriving at safe conclusions as to the equivalency of the beds in
330 PALEOZOIC TIME ā CARBONIFEROUS AGE.
the different coal basins, because the beds of rock as well as of coal ā even those
that are the thickest ā vary much at comparatively short distances over the
country. Moreover, as the basins are wholly disconnected, there is no chance
to trace even a single stratum from one to another. It is often assumed that
the Appalachian and Illinois beds were once united, and were afterwards
divided by the uplift of the Silurian about Cincinnati and extensive denudation
accompanying it. But it has been shown (p. 317) that this uplift probably
antedates long the Carboniferous Agej and, if this were so, the connection in
those latitudes is impossible. It is evident, therefore, that only the most general
conclusions on the subject of equivalency can be accepted as established facts.
The principal investigations on this subject are those of Lesquereux, who has
brought to it a thorough knowledge of the coal plants.