xt7wst7ds08n https://nyx.uky.edu/dips/xt7wst7ds08n/data/mets.xml Moore, Philip North, b. 1849. 1878  books b96-13-34908518 English Stereotyped for the Survey by Major, Johnston & Barrett, Yeoman Press, : Frankfort, Ky. : Contact the Special Collections Research Center for information regarding rights and use of this collection. Geology Kentucky. Coal Kentucky. Report on a geological reconnoissance of the region adjacent to the Kentucky & Virginia state line  : from Cumberland Gap to the Chatterawha or Big Sandy River / by P.N. Moore. text Report on a geological reconnoissance of the region adjacent to the Kentucky & Virginia state line  : from Cumberland Gap to the Chatterawha or Big Sandy River / by P.N. Moore. 1878 2002 true xt7wst7ds08n section xt7wst7ds08n 










GEOLOGICAL SURVEY OF KENTUCKY.

          N. S. SHALER, DIRECTOR.



              REPORT ON

       A GEOLOGICAL RECONNOISSANCE

            OF THE REGION ADJACENT TO THE


KENTUCKY & VIRGINIA STATE LINE,

  FROM CUMBERLAND GAP TO THE CHATTERAWHA OR
              BIG SANDY RIVER

              BY P. N. MOORE.

       PART IV. VOL. IV. SECOND SERIES.



W  TED -0 T-X SUVEY ST IAJOR.-SrO    -RRT , RYXOT-I, -Y.
                                    217 h 218

 This page in the original text is blank.

 



REPORT OF A GEOLOGICAL RECONNOISSANCE
  OF THE REGION ADJACENT TO THE KEN-
    TUCKY AND VIRGINIA STATE LINE, FROM
       CUMBERLAND GAP TO THE CHAT-
       TERAWHA OR BIG SANDY RIVER.


  The State line between Kentucky and Virginia, beginning
at a point a few hundred yards from Cumberland Gap, where
the three States of Kentucky, Tennessee, and Virginia cor-
ner, follows the crest of the Cumberland Mountain, which is
also the dividing ridge between the waters of the Cumberland
and Tennessee rivers, for about thirty-five to forty miles,
to the head of Crank's creek, a branch of Martin's Fork of
Cumberland river. It here leaves the Cumberland Mountain,
which turns more to the east; and follows the crest of the
Little Black Mountains, which now form the dividing ridge
between the just mentioned rivers, having on one side the
head branches of Martin's and Clover Forks of the Cumber-
land, and on the other those of the North Fork of Powell's
river.
  The State line follows the crest of the Little Black Moun-
tains to their junction with the Big Black Mountains, at the
head of Clover Fork of Cumberland, when it turns to the top
of the Big Black Mountains, which it follows to the head
of Poor Fork of Cumberland river, where the Big Black
Mountains abut against the Pine Mountain. The Big Black
Mountains lie partly between the Clover and Poor Forks of
Cumberland, and partly between the Poor Fork of Cumber-
land and the North Fork of Powell's river.
  At the head of Poor Fork the State line crosses to Pine
Mountain, which is here sometimes called the Laurel and
There is no accurate map of this region, and, in consequence, the distances given are
only approximations, as nearly accurate as could be obtained.
                                                      219

 
4   GEOLOGICAL RECONNOISSANCE OF THE REGION ADJACENT

sometimes the Cumberland Mountain, and follows its crest to
the end of the mountain, at Russel Fork of Chatterawha or
Big Sandy river, a distance of about thirty-five miles or more.
  It will be seen, therefore, that the discussion of the geology
of the region adjacent to the State line involves the exami-
nation and description of three mountain ranges-the Cum-
berland, Black, and Pine.

                THE CUMBERLAND MOUNTAIN.
  The Cumberland Mountain, along which the Kentucky-Vir-
ginia State line runs for such a distance, is identical with the
mountain of the same name in Tennessee, which forms for
some distance the upturned rim or edge of the -Cumberland
Table Land" of Prof. Safford's Tennessee Geological Report.
  It is a long narrow ridge, running in an east northeast and
west southwest direction, and varying in height from nine
hundred to two thousand feet above the adjoining valley.
The crest line of the mountain does not follow a straight
line; there are many minor curves and changes in direction,
but it preserves a general course about as stated.
  The mountain is formed of the tilted rocks of the Carbonif-
erous, Sub-carboniferous, Devonian, and Silurian periods, dip-
ping to the northwest at angles from fifteen to ninety degrees,
varying for almost every separate mile of its length. The
direction of the dip is also subject to local changes, which
are the cause of the changes in the course of the crest line
of the mountain. The crest line represents approximately
the strike of the rocks, for the mountain recedes or wears
away along a line at right-angles to the dip, A change,
therefore, in the direction of the dip, results in a change in
the direction of the crest line.
  The determining rock which forms the crest of the moun-
tain, and gives character to its topography, is always one of
the Conglomerate sandstones of the lower coal measures.
  Of these sandstones, there are a number, from seventy-five
to three hundred feet in thickness, separated by shales or shaly
sandstones, carrying beds of coal. These Conglomerates are
220

 
TO THE KENTUCKY AND VIRGINIA STATE LINE.



roughly divided into two series, an upper and lower. This di-
vision, at places, is well marked; at others, it cannot be traced.
There is a considerable thickness of shale or shaly sandstone
between the lowest of these Conglomerates, and the underly-
ing Sub-carboniferous limestone. These Conglomerates rep-
resent the single sandstone, which near the Ohio river lies at
the base of the coal measures. This increases in thickness
toward the south, and separates into several members. while
the space between, filled with shale and shaly sandstone,
grows thicker in proportion to the increase in the thickness
of the Conglomerates, and contains a number of coals.
  The total thickness of these Conglomerates and the inter-
conglomerate beds, all of which may be embraced under the
term Conglomerate series, is in the neighborhood of two
thousand feet. These Conglomerates can no longer, there-
fore, be strictly said to mark the base of the coal measures.
  The crest of the ridge is formed sometimes by the upper and
sometimes by the lower Conglomerates, depending largely on
the degree at which the rocks dip. Where the dip is gentle,
the upper Conglomerates come to the top, and the mountain
attains its maximum height; but where the dip becomes
steep, these retreat back on the northwest or Kentucky slope,
and the lower come to the crest, the mountain decreasing at
the same time until it is at its minimum, when the dip of the
rocks is steepest.
  These Conglomerates are usually quite pebbly, massive,
cliff-forming sandstones, yielding to erosion slowly, and, in
consequence, forming by far the most conspicuous feature in
the topography of the mountain. Fine exposures, in the
shape of splendid cliffs, from one hundred to four hundred
feet high, are seen all along the mountain face. The shales
between and below the Conglomerates are much more rarely
exposed, as they are usually covered by the talus from the
overlying sandstones. In fact, no complete exposure of these
beds has yet been obtained in this region, and it is unknown,
at this time, how many and what thickness of coal seams they
contain. The place of one coal is well ascertained; but, as
                                                        221



5

 
6   GEOLOGICAL RECONNOISSANCE OF THE REGION ADJACENT

it is nowhere opened for mining purposes, its thickness and
quality are as yet unknown. The -stain " of other coals has
been seen occasionally between the Conglomerates, but their
exact positions are not yet determined.
  The next most prominent member of the rock series of the
Cumberland Mountain, after the Conglomerate series, is the
Sub-carboniferous or St. Louis limestone. This limestone is
from four hundred to five hundred feet thick. It is seen at
many prominent outcrops on the mountain, the most- notable
of which is the cliff at the "Pinnacle," Cumberland Gap. It
is by no means so often exposed as the Conglomerate, for the
reason that, like the shales, it is covered by the talus, or the
broken weathered fragments from that sandstone. Its place
can, however, usually be determined by the bench which it
forms in the hill slope.
  Below the limestone, a fine-grained, greenish shaly sand-
stone, about one hundred and fifty feet in thickness, occurs.
It is the sandstone variously known as the Knob stone, in the
old series Kentucky Geological Reports, the Silicious, of Prof.
Safford's Tennessee Geological Report, and the Waverly, of
the Ohio Reports, which latter name has been adopted by the
present Survey. From its shaly structure, it is eroded so
easily and rapidly that it is usually covered either with its
own weathered fragments, or material from the rocks above.
It is only seen, therefore, in position where it is cut into by
the rapid streams on the mountain side.
  Immediately below the Waverly, and passing into it without
any distinctly marked line of change, is the Devonian black
shale. This shale is too widely extended and too well known
to need any special description here. It is from one hundred
to one hundred and fifty feet in thickness, with perhaps an
average of one hundred and twenty-five. Like the Waverly,
it is soft, and wears rapidly; so that it is usually covered, and
it is difficult to obtain exposures where its whole thickness can
be measured with accuracy.
  At places where the dip of the rocks is very steep, and the
mountain consequently low and narrow, the black shale is its
222

 
TO THE KENTUCKY AND VIRGINIA STATE LINE.



lowest rock. In this case, it is cut away to form the IIPoor
Valley," which uniformly occurs at the foot of the mountain,
between it and the range of foot-hills, called the " Poor Valley
Ridge," formed of the rocks of the Clinton or Dyestone and
the Medina Groups. Usually, however, there is a thickness
of from one hundred to three hundred feet of shales and shaly
sandstones, containing thin bands of limestone, at the base of
the mountain below the black shale, and in these the valley
is cut. These rocks overlie the Clinton or Dyestone iron ores
of this region, which are usually found in the Poor Valley
Ridge. For a portion of the distance these ores are found at
the foot of the mountain; but, as a rule, they lie in the upper-
most beds of the foot-hill range.
  These ores occur with great regularity along the foot of the
mountain for many miles, constituting in the aggregate an
enormous store of mineral wealth, that is as yet almost un-
touched. Their quality is good, their thickness and position
such that they can be mined cheaply, and this region only
lacks facilities for cheap transportation to make it one of the
most prosperous and extensive iron manufacturing districts of
the country.
  These ores will be described more fully in another report,
devoted especially to them.
  The Clinton or Dyestone Group, which forms so large a
portion of the rock structure of the Poor Valley Ridge, is from
three hundred to five hundred feet in thickness. It is com-
posed of shales and thin-bedded sandstones, with occasional
limestones. Below these rocks of the Dyestone Group, the
heavier-bedded Medina sandstone occurs, and, with the upper
part of the Cincinnati limestone, which is sometimes present,
completes the list of the rocks of the foot-hills of the Cumber-
land Mountain.
  All of the above described rocks, with the exception of the
Conglomerate, are seen only on the southeast or Virginia face
of the mountain; but they have been thus fully described, as
a knowledge of them is absolutely essential to any clear com-
prehension of its structure. On the northwest or Kentucky
                                                         223



7

 
8   GEOLOGICAL RECONNOISSANCE OF THE REGION ADJACET

slope of the mountain, only the Conglomerate, and the beds of
sandstone and shale of the coal measures immediately over-
lying it, are seen. The slope on this side is much more gentle
than on the other. It is usually a little less than the dip of
the rocks, or nearly the same; so that but a slight thickness
of rock above the Conglomerate is found on the mountain.
  At the base of the mountain, on this side, is a line of fault
or fold, as yet undetermined, which lies between the tilted
rocks of the mountain and the overlying horizontal coal-meas-
uire rocks.
  These rocks form the hills lying between the Pine and the
Cumberland Mountains, variously known as the Log and the
lack Mountains. They are formed wholly of coal-measure
rocks, lying nearly horizontally, and show a greater thickness
than in any other portion of Kentucky.
  Along this line of fault or fold, between the horizontal and
tilted rocks, there is usually a stream flowing, with a course
parallel to the line of the mountain. A series of such streams
is found along its whole length. They usually head against
one another at very low gaps, run in opposite directions until
they meet other streams flowing toward them, when they
leave the mountain and flow across into Cumberland river.
  Between Cumberland Gap and the point where the State
line leaves the Cumberland Mountain there are five principal
streams flowing at the foot of the mountain on the Kentucky
side. They are: Clear Fork of Yellow creek, Cubbage and
Browney's creeks, Martin's Fork and Crank's creek. Of
these, Martin's Fork is the longest and largest, being some
twenty miles in length before it unites with Crank's creek and
turns away from the mountain. Unlike the others, it heads
at the top of the mountain, at the point where Brush Moun-
tain, an outlier of the Cumberland range, the structure of
which has not been well determined, separates from it.
  Shillaley creek, a branch of Clear Fork of Yellow creek,
heads against Martin's Fork, at the top of the mountain, and
the two streams divide the Brush from the Cumberland Moun-
224

 
TO THE KENTUCKY AND VIRGINIA STATE LINE.



tain. Cubbage and Browney's creeks flow at the base of
Brush Mountain.
  Brush Mountain, as we now know it, seems to be a duplica-
tion of the Cumberland, caused by a fault in the Conglom-
erate beds. It runs parallel with the Cumberland Mountain,
and for a portion of its distance is about the same height; but
it falls away at the upper end to a little more than half. It
seems to be formed entirely of the Conglomerate and inter-
conglomerate beds; at least, no lower rocks than these were
found at its upper end, where Martin's Fork cuts deep be-
tween it and the main ridge. At this end, however, we have
the Conglomerate, probably the upper member, nearly hori-
zontal, or at least not dipping more than five degrees, showing
splendid cliffs two hundred and thirty feet high, while on the
other side of Martin's Fork, on the Cumberland Mountain,
the sandstones dip fifteen degrees or more. The position of
the rocks on the northwest face of Brush Mountain has not
been ascertained as yet. The rocks of the mountain have
evidently been raised to their present position by an uplift in
the same manner as those of the main ridge; but it is remark-
able that they should be so raised and still be so little inclined.
Our knowledge of the structure of this mountain is, however,
so imperfect as yet, that little can be told with accuracy re-
garding it.
  The height of Cumberland Gap above tide is stated, in
Prof. Safford's Tennessee Report, as one thousand six hund-
red and thirty-six feet. The height of the "Pinnacle," the
mountain just above the Gap, as ascertained by repeated
measurements with mercurial barometer, by Mr. William
B. Page, of the United States Coast Survey service, is two
thousand five hundred and one feet above tide. This meas-
urement was made from a bench-mark of a railroad survey
in the valley,on the Tennessee side. The height of the Pin-
nacle above this valley is one thousand two hundred and ten
feet, while it is one thousand three hundred and seventy-three
feet above the Yellow Creek valley, on the Kentucky side,
showing this valley to be one hundred and sixty-five feet
    VOL 1V.-15                                         15



9

 
10 GEOLOGICAL RECONNOISSANCE OF THE REGION ADJACENT

lower than the other-a relation which the valleys on both
sides of the mountain hold wherever observations have been
taken all along it, until after the State line leaves it.
  The Fort Hill, a knob a short distance above the Pinnacle,
rises considerably higher, and is the highest point in the
mountain for several miles in both directions. The mountain
then falls away toward the northeast, and at Lewis' Hollow,
one mile above, is about three hundred feet lower. It soon
recovers its usual height of about one thousand three hundred
feet, which it gradually increases towards the northeast. For
the first fifteen miles above the Gap the usual dip is from
twenty to twenty-five degrees to the northwest, although on
the slope of the mountain local dips as high as forty-seven
degrees are noticed. Gibson's Gap, four miles from the Pin-
nacle, is about one thousand one hundred feet above the
Powell valley, while the average height of the mountain is
some two hundred feet higher.
  Chadwell's Gap, about thirteen miles from the Pinnacle, by
way of the mountain crest, is between one thousand five
hundred and one thousand six hundred feet above the Powell
valley, with the general level of the mountain not more than
two hundred and fifty feet above. This gap is opposite the
centre of Brush Mountain, at the head of Martin's Fork.
  For the next five miles the mountain continues steadily to
gain in height, turning at the same time in a grand sweep
round to the east, until a point is reached which is known as
the White Rocks, so called from the conspicuous and pre-
cipitous cliffs of Conglomerate crowning the summit of the
mountain. This is the most prominent point in the whole
mountain, viewed from either above or below, extending so
far out to the east as it does, and at the same time holding
so great a height. The abrupt bastion-like front which this
point presents, outlined against the sky, can be seen for many
miles on either side. The mountain is here nearly two thou-
sand feet above the Powell valley, and, by barometrical
measurements by Mr. W. B. Page, United States Coast Sur-
vey, is shown to be three thousand four hundred and sixty
226

 
TO THE KENTUCKY AND VIRGINIA STATE LINE.



feet above sea level. The sweep of the mountain round to
the east is due to a change in the direction of the dip of the
rocks, which gradually change from northwest to north, and
from north to north twenty degrees east, which is the direc-
tion at this point, while the angle of dip is quite gentle, being
only from thirteen to fifteen degrees.
  The Conglomerate capping the ridge forms at one place a
cliff nearly four hundred feet in height, which is a little more
than perpendicular, overhanging a few degrees. These cliffs
are unusually prominent along the face of the mountain for
the next three or four miles.
  Soon after passing the White Rocks point the dip of the
rocks once more changes to the west of north, and the course
of the mountain range turns in sympathy back toward the
northeast.
  The dip of the rocks becomes much steeper, and the moun-
tain loses proportionally in height. At Britton's Gap, about
seven miles above, where the mountain was crossed on this
journey, the rocks are vertical, or, in some cases, overthrown
and dipping to the southeast about eighty degrees. The
height here, by aneroid barometer, is only nine hundred and
fifty feet above the Powell valley, or about half the height at
the last point of observation.
  At Brierfield's Gap, three miles above this, the height of
the top of the mountain is only nine hundred feet above the
valley. The Poor and the Powell valleys, on the Virginia side
of the mountain, grow narrow with this change in the dip, as
only the edges of the rocks are presented for erosion. The
range of foot-hills, called the Poor Valley Ridge, follows in
miniature the changes in elevation of the mountain, rising to
about four hundred feet at the White Rocks, sinking away to
about two thirds this height at the last described places, and
then rising again to nearly five hundred feet at the next ele-
vation in the mountain at Crank's Gap, which is about ten
miles above. Here the dip of the rocks has once more be-
come very gentle, from eighteen to twenty-five degrees, and
the mountain is about one thousand five hundred to one thou-
                                                        227



ItI

 
12 GEOLOGICAL RECONNOISSANCE OF THE REGION ADJACENT

sand six hundred feet above the valley. Its elevation above
sea level is not known, but it is probably somewhat less than
the White Rocks point. The mountain at this point is very
broad-fully twice its usual breadth. Where the rocks were
steeply inclined, or vertical, no rocks higher than the Con-
glomerate seem to have shared in the disturbance, or, if
they did, all traces of them have been worn away. The
mountain is consequently narrow, and Martin's Fork, the
stream at the base of the mountain, flows close to the top
of the Conglomerate in a very narrow valley, so narrow that
there is but little arable land in it.  The mountain along
here shows. from the Kentucky side, a succession of splendid
outcrops of Conglomerate, standing on edge, or very steeply
inclined. It holds this character along the lower part of
Crank's creek also, where that stream is almost exactly sim-
ilar to Martin's Fork; but along its upper portion the valley
is wider, and is cut in rocks geologically higher, the shales
and shaly sandstones above the Conglomerate. A consider-
able thickness of these rocks, here,share in the elevation of
the Cumberland Mountain, and it is owing to this fact, to-
gether with the slight degree of dip, that the mountain at
Crank's Gap is so broad. The road from Mt. Pleasant, Ken-
tucky, to Jonesville, Virginia, crosses at this gap. It is in
reality no gap at all, but simply a place where the road crosses
the mountain, and that at one of its highest points. This
point runs well out to the east, and from the summit the
Cumberland range can be seen down to Speedwell, in Ten-
nessee, twenty miles below Cumberland Gap, a total distance
of forty or fifty miles.
  About four miles above this point the State line leaves the
Cumberland Mountain, and crosses at a low gap at the head
of Crank's creek, between that stream and one of the branches
of Powell's river, to the Little Black Mountains.
  The Cumberland Mountain turns still further to the east,
and is henceforward known as the Stone Mountain. The
so-called gaps, which have been mentioned, are usually only
slight depressions in the crest of the ridge, through which the
228

 

TO THE KENTUCKY AND VIRGINIA STATE LINE.



mountain paths or trails cross. For thirty-five miles above
Cumberland Gap there is no gap of more than three hundred
feet depression below the general level of the crest, nor is
there in this distance any wagon road across the mountain.
Between thirty-five and forty miles above, however, the North
Fork of Powell's river has cut through the mountain and
made a water-way known as Pennington's Gap. The moun-
tain,here,is only about one thousand feet high, and the rocks,
from the Silurian to the Carboniferous, are nearly vertical,
with a strike north 30 east. The North Fork of Powell's
river, which cuts through here, drains a considerable area
lying between the Little Black and the Cumberland Moun-
tains, known as the " Pocket." The line of disturbance does
not, here, seem to reach the rocks much higher than the Con-
glomerate. In this gap a coal is exposed, standing vertical,
about thirty-five feet below the upper Conglomerate. The
coal is reported thirty inches thick. It is said that there are
two other coals found vertical near this point, but they were
not seen by the writer.
  The scenery at Pennington's Gap is grand in the extreme.
The river has made a narrow cut through the mountain, in
which the walls of vertical Conglomerate are seen hundreds
of feet high, rising far above the rocks on either side, rugged
and bare.
  Eighteen miles above, at the Big Stone Gap, in the Cumber-
land or Stone Mountain, another fork of Powell's river, called
also the North Fork, and sometimes the Roaring Fork, has
cut a similar water-gap through the mountain, which is here
about the same height as at the last place; but the rocks
are not quite so steeply inclined, dipping only about sixty
degrees. The stream at this gap drains a considerable area,
lying between the Big Black and the Stone Mountains, and
the divide between the waters of the Powell and Guest's
rivers, the latter a tributary of the Clinch.
  This is the last water-gap cut through the Cumberland
Mountain, which extends about twenty miles further to the
                                                        229



13

 
14 GEOLOGICAL RECONNOISSANCE OF THE REGION ADJACENT

east, and finally ends near Guest's river, in Wise county,
Virginia.
  These two gaps are the natural ways to give access to the
boundless stores of coal which lie north of the Cumberland
Mountain. Through them, with little expense, the coal can
be brought, which will, in the future, supply fuel to the great
non-coal-bearing country to the south. Above the Big Stone
Gap the Powell valley gradually narrows, the Powell Moun-
tain or range approaches the Cumberland, and finally unites
with it above Little Stone Gap, at the extreme head of Powell's
river.
  From Big Stone Gap the Cumberland Mountain is low,
rarely over one thousand feet in height above the valley.
About ten miles from this last mentioned point the wagon
road to Gladesville crosses the mountain at Little Stone Gap,
which is cut about three hundred to four hundred feet below
the general level of the crest, and is about six hundred feet
above the valley.
  The lowest rock seen on the south face of the mountain is
the Devonian black shale. It is the surface rock for a con-
siderable area near the head of the valley. It dips to the
north very slightly; but above it we have the Waverly and
the St. Louis limestone, increasing in steepness of dip as we
ascend. The limestone dips about forty-five degrees nearly
due north, while on the north slope of the mountain, a few
hundred yards after passing the gap, the Conglomerate and
inter-Conglomerate beds are standing vertical, or dipping to
the north from eighty to eighty-five degrees. Between the
Conglomerates there is a coal exposed by the roadside, stand-
ing nearly vertical. It was seen about thirty inches thick.
  The only published information in regard to the geology of
this region which has come to the notice of the writer, is a
paper by Prof. J. P. Lesley, the distinguished State Geologist
of Pennsylvania, read before the American Philosophical So-
ciety, April 2Ist, 1871, on the geological structure of Taze-
well, Russel, and Wise counties, Virginia.

 
TO THE KENTUCKY AND VIRGINIA STATE LINE.



15



  In this valuable and interesting paper, Prof. Lesley gives a
section at Little Stone Gap, which he states has not been seen
by him, but is published from information given to him. This
section correctly shows one vertical Conglomerate with the coal
above; but it also shows a fault running lengthwise through
the mountain, with the lower Silurian limestone forming the
south face of the mountain. From the description given just
above, it will be seen that this section is very incorrect.
  There is no fault running lengthwise through the mountain;
on the contrary, it shows at this place only what may be called
the normal structure of the Cumberland Mountain. There is
no Silurian limestone exposed on the mountain at this place.
The lowest rock seen, both geologically and topographically,
is the Devonian black shale.
  Prof. Lesley's informant has evidently mistaken the massive
St. Louis limestone, which occupies its usual place on the
south face of the mountain, for the lower Silurian, and Prof.
Lesley himself was the more ready to accept the statement,
supposing this to be the westward prolongation of the great
Clinch River fault, which terminates the coal field above
Guest's river, beyond the end of the Cumberland or Stone
Mountain.
  The distance from the end of the Cumberland Mountain,
at Guest's river, to Cumberland Gap, is about eighty miles.
From Ctumberland Gap, to the southwestern end of the same
mountain in Tennessee, as stated by Prof. Safford, is about
forty miles. Its total length is, therefore, about one hundred
and twenty miles, in which distance it is broken by only
five gaps, deep enough to be more than serrations in
the crest line. These are: Bruce's and Big Creek Gaps, in
Tennessee, Cumberland, Pennington's, and Big Stone Gaps.
Of these, all except Cumberland Gap are water-gaps, while it
is cut three fourths of the distance down from the top of the
mountain.



The reader should keep in mind the distinction between the Cumberland Mountain as
described here and the -Cumberland Table Land" which occupies so large a portion of
the area of Central Tennessee.
                                                          231

 
I6 GEOLOGICAL RECONNOISSANCE OF THE REGION ADJACENT

  It affords one of the most feasible passages for a railroad,
for the reason that, while the other gaps afford a much easier
passage through the mountain itself, yet, to get to them, a
railroad would be compelled to cross the much higher moun-
tains between the Cumberland river and mountain, while at
Cumberland Gap the Yellow Creek valley affords an easy
way, with light grades to the very foot of the mountain.
  There is, perhaps, a better route for a railroad offered
through Pennington's Gap, crossing the divide between the
waters of Powell and Cumberland rivers at a very low gap at
the head of Crank's creek, which flows at the base of the
mountain on the north side; but this is somewhat less direct
than via Cumberland Gap.
  Above Guest's river, in Virginia, the coal field terminates
with a fault which brings the rocks of the Knox series (using
the Tennessee nomenclature) up against the coal measures.
This fault is unaccompanied by any great topographical ele-
vation, and the disturbance in the rocks of the coal measures
is comparatively slight, not extending far back north of the
fault. The limestones on the south side of the fault, how-
ever, are very much disturbed, showing numerous local flex-
ures and cross-folds close to the line, while further back they
dip steeply away to the southeast. From here south to Clinch
Mountain, along the road to Abingdon, Virginia, the rocks of
the Knox series, and, in a few cases, the Trenton limestone,
are seen. The valleys of the small streams are cut in the
imbricated edges of these rocks, which are repeatedly faulted,
the same series of limestones and shales being crossed a num-
ber of times, and usually dipping in the same direction, to the
southeast.
  At Clinch Mountain the geological series as high as the
Devonian shale is represented, while just beyond, south of
the Holston river, another fault occurs, which once more
brings the lower or middle Knox series to the surface, and
we then have a repetition of the features just described: the
rocks dipping to the southeast, and occasionally faulted; the
upper part of the Knox series and the Trenton limestone
232

 
TO THE KENTUCKY AND VIRGINIA STATE LINE.



forming, for the most part, the surface rock as far south as
Abingdon. The Clinch Mountain here, as further southwest,
is capped and shaped by the massive Medina sandstone,
which, with the other rocks of the mountain, dips to the
southeast. The principal geological and topographical feat-
ures of this region are well shown in the map accompanying
the paper of Prof. J. P. Lesley already referred to.
  The fault,which ends the coal measures, lies on the north
side of Clinch river, for the most part close to it, and at one
point even crosses to the south side of the river. It is shown
by Prof. Lesley to extend along the north side of the river to
its head and beyond. About twenty miles above Guest's river
the fault line runs several miles north of Clinch river, leaving
room between it and the river for a fertile valley, known as
New Garden. This is principally drained by Lewis creek.
The fault line crosses at the very head of this creek, nearly
half way up the dividing ridge or the Big Mountain, the
divide between the waters of the Clinch and Big Sandy or
Chatterawha rivers. The exact height of this mountain was
not determined, but it is probably over one thousand five
h