THE
AMERICAN JOURNAL OF SCIENCE
[FIFTH SERIES.1
ART. XIX.ÄMinor Faulting in the Cayuga Lake Region; *
by E. TATUM LONG.
INTRODUCTION.

	The drought of the summer of 1921 caused many of the
creeks in the vicinity of Cayuga Lake to run almost or
entirely dry. Advantage of this condition was taken to
make a rather detailed study of rock exposed in their beds
and on their banks, with a view to adding if possible some
information as to the nature of the numerous small faults
of the region, and in particular to a very unusual mani-
festation of faulting shown on a small scale in Salmon
Cr. at Ludlowville, N. Y. (See map, fig. 1.) For some
time these faults had caused considerable speculation but
weather conditions made field investigation impossible.

	As it soon became evident that knowledge of the general
structure of the region would give little clue to the par-
ticular features here exposed, the beds of some thirty odd
creeks covering a distance about 20 miles to the north of
Ludlowville and 4 miles to the south, were traversed, in
addition to the Whole of the east shore of Cayuga Lake,
except the lower nine miles. The Lehigh Valley Railway
tracks for this same distance and about six continuous
miles of the west shore above Taughannock, with a few
additional shorter stretches to the north, were also cov-
ered on foot so that all details could be closely observed
and contact readings made of the dip of the strata. A
launch was employed in order that sight readings could be
made on both shores, a distance of about 30 miles being cov-
ered in this way. These readings proved more accurate
and more representative, as several feet instead of inches
could in this way be covered by the clinometer of a Brun-

	* Grateful acknowledgment is herewith given Prof. A. J. Eames and
Prof. V. E. Monnett for helpful criticism of the manuscript.

AM. JOUR. SCI.ÄFIFTH SERIES, voL. III, No. 16.ÄAPRIL, 1922.
17

231

ton which was used for most readings. An average dip
of a little less than 1~ (about 60') was thus established over
by far the greater part of the lake shore. The dip being
so gentle it is almost impossible to get accurate readings
even by sighting with a level clinometer on a telescope,
hence the impracticability of contact readings.

	The presence or absence of cliffs, as well as that of the
terraces, in some places so conspicuous, is due to the

	FIG. 2.-The Tully Limestone between Portland Pt. and Idlewood, 
east shore of Cayuga Lake. The Tully is here shown capping the 
Hamilton with the usual southerly dip. Though but 20' thick it forms a 
conspicuous terrace with a corresponding dip to the south.

nature of the formation exposed at a given locality,
whether hard or soft. The height of the cliffs and ter-
races, sometimes over 100' above the lake-level, is due to
the position of the two dominatingly hard layers of the
districtÄthe Tully limestone immediately overlying the
Hamilton shale, and the Encrinal bed of the Hamilton,
somewhat over 100' below. These two resistant layers
form waterfalls in all creeks which cross their outcrops,
the height of the fall being dependent upon the elevation
of the hard ledge.

232

Major Structural Features.

	The Watkins Glen-Catatonk folio deals with the
region south of a point called Esty's Glen which is located
about four miles north of Ithaca. To the north of this
point little work has been done, but one would expect to
find a continuance of the large features as shown, by
E. MI. Kindle,1 to exist in the region to the south, including
not only south central New York but northern Pennsyl-
vania as well. This structure is considered by him to
be the northward dying out of the results of the Appa-
lachian Mountain making whose trend and characteristics
it shares. The sinuous axes of the broad low folds of the
Chemuing and Portage of this area are given in a sketch
map on page one hundred of the folio, as well as on the
Areal Geology sheet. The average trend is slightly N-E
to S~MT of a true east-west line and would imply pressure
from a direction S.SE resistance being encountered in a
N.NW direction. Eastward they swing to a more nearly
E-W course. From the south to the north end of Cayuga
Lake successively older rock are continuously met, the
general dip being to the south, though it is not constantly
so. The order of succession is: Portage at Ithaca and to
the'north, until the Genesee appears in the bottom of the
cliffs about half a mile south of Esty's. Something over
a mile to the north of this the Tully emerges from the
Lake and though seldom over 20' thick, dominates the cliff
face of Cayuga Lake (see fig.2) with but one break at the
mouth of Salnion Cr., for a distance of 14 miles to the
north after which for three more miles it makes falls
heading deep ravines in the Hamilton shale beneath. The
steepness and occasional great height of the cliffs of
Cayuga Lake are therefore all the more remarkable since
they are cut in the soft shale of the Hamilton for over half
of the 40 miles of its shore line.

	The quarry in the Tully limestone at Portland Pt.
seems to be located on the crest of the major anticline of
the whole Cayuga area at an elevation of 640'. Beds dip
away from this point to the south for a short distance at
the rate of 6~, but after 14 mile assume the usual dip of
about 10. This continues with but slight variation to the
south end of the lake. To the north, the beds dip a little

	1 Watkins Glen.Catatonk folio 169, U. S. G. S., pp. 98-111.


233
less than 10 northward for about a mile, when they
assume approximately a horizontal position for another
mile or so, before again dipping to the north at a rather
higher angle than before. This is again followed by a
horizontal area at Ludlowville. A short distance north-
west of the boundary of the accompanying map the dip
is reversed and the beds continue a southerly dip to the
northern end of the lake, some thirty miles distant.
	The major fold will here be spoken of as the Portland
Point anticline, from the present name of the point, though
it was formerly known as Shurger `s Point and is so
named on the topographic sheet. Its axis across Cayuga
Lake trends nearly 50 south of E-W with a westerly pitch
of about 44' per mile, that is, about «~. This westward
pitch of The anticline combined with the general southerly
dip of the strata serves to give an ever increasing height
to the strata in a northeasterly direction.


Faults in the Encrinal limestone.

	Faulting, like the other dynamic movements of the
region, is on an unobtrusive scale and would deserve little
or no attention were it not for the possibility of throwing
some light on the history of the region, indicating some-
thing of the nature and direction of the forces applied,
and illustrating in nature, even though in miniature, some
of the principles involved in rock movement. All of the
faults under observation occur in the Hamilton shale.
The difference in physical properties between the Encrinal
bed of the Hamilton and the vastly greater shaly portion
throw the faults therein occurring into two obvious
classes, though both are of the "low-angle" type. Those
in the Encrinal are conspicuous enough to one on the look-
out for them, but undoubtedly there are distributed
through the shale countless thousands, the existence of
which one will never guess. Vast thicknesses of the shale
have no visible bedding planes and even in situ are so
broken up into small flat lenses, often less than an inch in
either direction, that only by virtue of an offset in some of
the numerous joint planes is the presence of a fault
detected. But little is therefore known of the movements
within the shale, for its tendency to split up into this mnl-
titude of lamella~ at once destroys any record which might

234	

have been preserved on the fault plane. It is almost
impossible to get data for the third dimension and impres-
sions are correspondingly vague.
	Quite the reverse is the case in the Encrinal layer. In
the locality of Ludlowville and on the opposite shore,
faulting is more frequent than farther north, and the
Encrinal bed here consists of nearly two feet of coarsely
comminuted crinoid fragments containing well-preserved
fossils of good size. It is hard and compact, though
	FIG. 3.ÄStriated columnal structure due to movement under 
compression
along fault planes in the Enc.rinal layer between Crowbar and 
Willow Cr.,
west shore Cayuga Lake.
coarsely crystalline, forming ledges or waterfalls as the
conditions determine; a typical "competent" bed, in
which the faults conform to the laws of shearing under
horizontal compression, where the direction of least
resistance is both upward and downward into the com-
aratively mobile shale. The fault planes dip both to
the north and the south at angles varying from 200~30o,
and on both sides of the plane show striated columnar
structure produced by movement under pressure (see
fig. 3). The most numerous collection of these faults is
found on the west shore of the lake midway between
Crowbar and Willow Cr. and in a second strip of Encrinal

235

north of Willow Cr., the first on the south limb of the anti-
dine, the second on the north limb, the dip on both being
slightly less than 10.

	FIG. 4.ÄIntersecting faults in the Encrinal layer between Crowbar 
and Willow Cr. west shore Cayuga Lake. Notice the change in angle of 
dip as the faults enter the underlying shale, as well as the 
wedge-shaped block lifted up by the horizontal pressure.

	Fig. 4 will bear repetition here as giving, from nature,
an example of faulting strikingly similar to the results of
one of Daubr‚e `s famous experiments, as shown in fig. 5ù2
The block subjected to direct pressure from both ends
was a mixture of plaster, beeswax and resin, made to
approach natural conditions as nearly as possible and in
which were developed fractures formed at angles of about
450 to the direction of compression. The wedge shape
of the fault block produced in the Encrinal, though of
such small size as to almost forbid comparison, seems to
illustrate a movement similar to that suggested by
Mr. R. T. Chamberlin in his article on "The Appalachian
Folds of Central Pennsylvania. "~

	2Fig. 5 is a photograph of plate II, fig. 3 accompanying a 
discussion on p. 316, taken from "Etudes synth‚tiques de g‚ologie 
expdrimentale, vol. I, by A. Daubree.
	3 Chamberlin, R. T., Jour. Geol., vol. 18, No. 3, 1910 (especially 
pp. 246-259).


236
	In the Encrinal bed the dip of the fault plane is 220
to the north and 300 to the south, but as soon as it enters
the shale below it swings around and wi~in a couple
of feet has assumed a 20~ dip to tIfU~4h instead
of 30~ and a 100 dip to the north instead of 22g.
At the intersection of the faults some of the rock is
broken away, which may give a false impression, but by
projecting the fault planes across the intersection it would
appear that the plane C D was the older, though older
possibly only by the time it takes to make a fault, for it
seems to be cut by the plane A B with a slight off&et of
not more than 1". The wedge has been raised about three
	FIG. 5.ÄResults of pressure applied to a block of plaster, wax 
and resin,
in an experiment of A. Daubr‚e. Notice the wedge block so similar 
to Fig.
4 above.
inches and the striated columnar structure indicates
movement in a direction about N 15~ E, the strike of the
planes being approximately N 750 W. Owing to the posi-
tion of this and several nearby faults accurate measure-
ments were impossible. A comparison of fig. 4 with
fig. 10 in the article on "Low-Angle Faulting" by
Mr. R. T. Chamberlin and Mr. W. Z. Miller4 will at once
prove interesting and instructive. Here in nature is a
striking demonstration of the trustworthiness of their
experiments. Of course one of the intersecting faults
must be eliminated in one's mind to make the analogy
really good.
	But this little fault goes even farther. Traced back and

Chamberlin, R. T., and Miller, W. Z., Jour. Geol., vol. 26, p. 
27, 1918.

237

upward into the overhanging vegetation on the south side
for a few inches there is evidence that after leaving the
hard Encrinal bed below, the fault again lowers its dip in
passing into the shale above. This is a very unusual
exposure as the shale in other observed cases has been cut
from under the hard limestone layer and all trace of
faulting obliterated.
	FIG. 6.ÄOutcrop of Encrinal layer at the beginning of the high 
dip just
south of Portland Pt., east shore of Cayuga Lake.
	Just opposite Crowbar and 14 mile south of Portland Pt.
the Encrinal appears emerging from the lake with a dip
rather steeper than usual. This 50 dip to the south cor-
responds with the increased dip of the Tully above while
approaching the nearby crest of the anticline at Portland
Pt., 14 mile north (fig. 6). In it one fault was seen with
a dip of 30~ north and striations trending about N 80 E.
The position was such as to make an accurate reading of
the striated columnar structure impossible.
	On the north limb of the anticline about one mile north
of its crest and just north of the bridge over Salmon Cr.
near its mouth at Myers, the Encrinal appears in the west
bank some feet above the village street with a dip of 10 N.
Joints and what appear to be faults occur, but the cliff is
too steep to make this part of the bed accessible. Around
the second turn up stream it again appears in the other


238
bank with a cliff facing N 480 B. This is most accessible
and where it crosses the bed of the creek gives a contact
reading for dip of nearly 20 N. This is undoubtedly too
high. Of all observed, here was found the best one for
measurements, along with several imperfect ones. Just
before the Encrinal layer crosses the creek a fault with a
dip of 25~ N is exposed. Only the foot wall remains, thus
greatly facilitating the reading of both dip and striated
structure. The latter is N 40 B, the only positively
accurate reading for the direction of movement as shown
by the columnar structure on the fault planes. This read-
ing as all others is corrected for a magnetic declination of
8~, according to the U. S. G. S. quadrangle for the area.

	The following table will give some idea of an average iii
the faults:

Faults dipping south
angle of dip direction of striae

1.	 20¡-25¡ S.	about N. 6¡ E.
2.	 25¡ S.
3.	 30¡ S.	N. 15¡ E.
	strike about
	 N. 75¡ w.

4.

5.

Faults dipping north
angle of dip	direction of striae
20¡ N.	about N. 6¡ F.
28¡ N.	N.8¡ E.
22¡ N.	N.15¡ E.
strike about
 N. 75¡ W
25¡ N.	N.4¡ E.
strike N. 86¡ W.
30¡N.	N.8¡E.
strike N. 72¡ W.

Nos. 1, 2 and 3 occur just north of Crowbar where cliff and shore  line = N. 40¡ W.
No. 3 is shown in fig. 5.
No. 4 is in Salmon Cr.; readings accurate within a fraction of a  degree.
No. 5 is at Portland Pt.

	For a discussion of the origin and results of rotational
strain, to which type of faulting the above appear to
belong, the reader is referred to C. K. Leith's "Struc-
tural Geology" and to the above mentioned article on
"Low-Angle Faulting." An attempted summary would
not do the subject justice, but two points may be empha-
sized. It is known that the great forces, which raised
thousands of feet of sedimentaries into the Appalachian
Mts., were applied in a practically horizontal direction.
"The planes of greatest tangential stress should there-
fore dip at angles somewhere in the neighborhood of 450
and may plunge downward or upward."5 This angle of
	
5 Chamberlin, R. T., Appalachian Folds of Central Pa., Jour. 
Geol., vol. 18, p. 247, 1910.

239

45¡, however, may be modified and greatly reduced by a
number of conditions. Two in particular apply to the
case in hand. As brought out in the article on Low-Angle
Faulting, 1. to lower the angle of the fault plane means,
to decrease resistance by friction as produced by normal
compressive stress; hence the avenue of least resistance
will be taken. 2. "Rotational strain may be developed
from horizontal compressive stresses, in heterogeneous
material by bedding or similar structure, which present
differences in competency. ` `~


Deductions.

	From the above facts as shown by the faults of the
Encrinal layer of the Cayuga Lake region it may be
assumed that the forces which produced them worked
approximately horizontally and came from a direction
between 4¡ and 15¡ west of south. This is a rather sur-
prising development in view of the preceding statement
that the region belonged to the outskirts of the Appalach-
ian province and had shared its history even though in
less active form than the mountainous tract. Some inti-
mation of the fact might have been discerned in the pro-
gressively changing curve of the axes of the anticlines as
shown in folio No. 169 page 100 as they turn from a gen-
eral SSW-NNB to an easterly direction. So ingrained,
however, is the idea that all pressure as applied to the
Appalachians must come from the southeast that the
warning passed unnoticed.

	In northwestern central Pennsylvania, as well shown
on the U. S. topographic map, there occurs a sharp turn in
the trend of the Appalachians, with convexity N-W,
swinging them across northern Pennsylvania and south-
central New York in a nearly east-west course. This
soon again turns and they pass northward through New
England in the usual NNE direction. Lines drawn at
right angles to the trend of the second curve which occurs
in south-eastern New York would converge not far east of
Cayuga Lake, which means that this region is practically
due north of the east-west segment. The fact that the
axis of the Portland Pt. anticline crosses Cayuga Lake
	
6 Chamberlin, R. T. and Miller, w. Z., Low-Angle Faulting, Jour. 
Geol., vol. 26, p. 44, 1918.


240
a few degrees NW-SE of a true E-W line is, therefore, in
keeping with the other surprising fact of the direction
whence came the pressure developing the faults of the
Encrinal layer, and in reality is what should be looked for,
if truly related to the Appalachian Chain.
A dike which gives some collateral evidence.
	A feature which, on first sight, might in some respects
seem at variance with the previously expressed facts, is
the presence of a peridotite dike on the crest of the major
anticline. It was exposed five or six years ago in the east-
ern end of the quarry operated by the Portland Cement
Company at the point given its name. Rising from the

	FIG. 7.-Inclusions of Tuhly limestone in a weathered peridotite 
(serpentine) dike at Portland Point. Notice the fine bedding planes 
of the limestone.

Hamilton, which forms the floor of the quarry and cutting
entirely through the Tully limestone it intrudes several
feet into the Genesee shale above. For the region it is
quite sizable, varying from 12" to 18". The strike of the
dike, N 3%60 W, is not in conformity with the postulated
direction of movement, which however is to be accounted
for by the fact that the dike is obviously here following the
course of one of the numerous joints belonging to the
N-S system. Its contact with the country rock is often
very close, there being no evidence of filling, but on the
other hand there are many places where the contact is
ragged, streamers of the magma having entered the lime-
stone and in some cases pieces of the Tully being broken
off and incorporated in the peridotite. (See fig. 7.) Con-

241

tact metamorphism is not conspicuous but a gradation of
texture is frequently noticed and the limestone is often
indurated for an inch or more. Calcite has very nearly
filled all the cavities opened up and on this soft medium
is recorded the usual N-S horizontal movement of the
region. So evidence other than faulting falls in line.
The north and south walls of the quarry very nearly par-

	FIG. 8.-Horizontal faulting in the Hamilton shale at the big 
Falls, Ludlowville, N. Y. The fault plane is just above the surface of the 
pool.

allel the axis of the fold so that the curved lines of dip
shown in these two walls as well as the eastern, together
with discrepancies iii dip indicate a torsional movement,
elevation at no two corners corresponding.

Faults in the Hamilton Shale.

	Quite another type of faulting from that already dis-
cussed is found in the shaly members of the Hamilton.
Here faults occur which are either movements along bed-
ding planes or parallel with them, on through various


242

angles up to those very nearly vertical. One good exam-
pie of the horizontal type is shown at the water level of
the pool at the foot of the big Fails at Ludlowville, north
of the village, and just below the dam. (See fig. 8.) The
disp1~icement is probably six inches. As the pooi does
not dry up even in time of drought and no boat is pro-
vided for the convenience of visitors it was impossible to
get nearer the fault than a hundred feet or so. It is about
35' below the Tully, the movement offsetting joints of the
N-S system, so that the upper mass was moved eastward
relative to the lower mass. This offset of the joints is
only the apparent displacement. The cliff faces very
close to due south, its trend being E-W, with no dip in
either direction which could be detected with a Brunton
clinometer or a telescope clinometer even by distant sight-
ing. As the streams always hug the north sides of their
courses it is to be inferred that a slight northerly dip
must be present. Taking the direction of pressure as
previously calculated at an average of about 100 west of
south, the chief movement will be in a general N-S direc-
tion, the E-W component representing only the very small
part played by the 10~ deviation from N-S. As the fault
does not.persist for any very great distance it is safe to
infer that the maximum displacement is nowhere great.
This locality is about two miles north of the crest of the
anticline at Portland Pt. and hence on the northern limb,
the dip of which is very far from constant. It appears
to be located on a second horizontal area, another level
district occurring about 100' higher and half a mile nearer
it.	Instead of being due to pressure this fault may possi-
bly, though not at all probably, be due to local relaxation
and hence belong to a type intimately connected with val-
leys and which will be discussed in connection with the
wedge fault block to follow.
	Mr. G. C. Matson in an article on "Peridotite Dikes
near Ithaca, N. Y. "7 calls attention to several dikes not
here considered. One group of four is above the high
fall over the Genesee shale, in a tributary to Salmon Cr.
just northeast of Ludlowville. "Three of these have been
faulted; the fourth does not reach up to the fault plane.
The amount of displacement is about two feet." 8   From

7 Jour. Geol., vol. 13, p. 265, 1905.
8 Ibid

243

this reference a horizontal fault is to be inferred and judg-
ing from the small offset a displacement similar to the
fault at the big Falls from which this is but a half mile
distant in a direction nearly due east.
	Immediately east of the bridge crossing Salmon Cr. on
the road entering Ludlowville from the south is a fault of
most unusual appearance. The face of the bluff in which
it occurs trends N 730 iE. that is, it faces in a general
northerly direction. Running from a point somewhere
under the bridge for over 100' to the east there is another
horizontal fault which ends abruptly against a joint plane.
This too is at low-water level but over 20' below the first

	FIG. 9.-Wedge-shaped block between a horizontal fault just above
water-level, and an oblique fault dipping toward the left margin of the
photograph. Easily detected by the offset of the joints.

one mentioned. Just across the sluice to the east of the
bridge and 9' above the horizontal fault another fault
plane has been developed which dips down at an angle of
8¡ and meets the lower one just where it encounters the
joint plane. Cutting the face of this bluff are a number
of well-marked joints belonging to the N-S system. The
two faults form a wedge-shaped block between them,
which as seen in fig. 9 is thrust inward, that is to the east,
but exhibits no evidence of crushing at its point. The

244

amount of offset, as measured in this case, is quite uni-
formly 6" on both faults. The junction of the two faults
with the joint plane has made a point of weakness in
which the creek has cut a miniature cave of a few inches
but in the absence of a brecciated zone and a decrease in
the offset of the joints in approaching the point of the
wedge it seems that the force applied must have been
oblique to the section exposed rather than parallel with it.
At the intersection of some of the joints with the upper
fault plane a curved surface has been developed on the
joint planes, suggesting a drag movement so often seen in
connection with faulting. The direction and amount of
offset is easily seen, owing to the presence of the joints,
and corresponds quite closely with the fault at the Falls.

	The face of the bluff trending as it does N 73¡ E gives a
very small angle of about 11¡ between it and a section
along the strike of the structure of the region, the axis of
the main fold being taken at N 85~ W. One would, there-
fore, expect as in the previous case that by far the largest
part of the movement would not be disclosed. As the
sluice ran at right angles to the bluff it was hoped that
some information in the third dimension might be gained
but the broken character of the shale had erased any evi-
dence if such ever existed. It was finally noticed that at
the intersection of one of the east-west and one of the
N 80 E joints where crossed by the dipping fault plane
about two square inches of the surface of the fault were
exposed; this showed an unmistakable dip into the bank,
that is to the south, but the surface was too small and
poorly situated to get any accurate readings. However
the dip south was apparently not less than 80 at the line of
outcrop. Presuming that this dip continues, regardless
of what its angle may be, it doubtless ultimately joùins the
horizontal fault, from which it seems likely that it is a
branch. This being the case we have here a transverse
section of the two faults rather than a longitudinal sec-
tion as at first appeared. The movement of the wedge
block was therefore not primarily in and eastward, but
was northward. The deviation to the west, of the forces
coming from the south which produced the faulting, plus
a slight torsional movement, would swing the joints out of
alignment to the extent of six inches and the compari-
tively mobile shale would accommodate itself to the

245

oblique pressure when it could hardly have done so in the
face of direct compression.
	The occurrence of the three above faults in such close
association with a large sized stream of extensive cutting
power brings up a question which may be raised by some.
Along the banks of many of the streams in the vicinity of
Cincinnati, Ohio, there occur in the Eden shale small over-
turned folds, sometimes advanced to the stage of thrust
faulting. (Fig. 10.) These are usually found on the
	FIG. 10.ÄFold in Eden shale, West Fork Cr., Cincinnati, 0. 
Supposed
to be due to relaxation resulting from stream erosion.
under-cut side of terraces and are beginning to be recog-
nized as produced by relaxation due to rock removal by
stream erosion, rather than by direct pressure. These
streams are all post-glacial whereas Salmon Cr., N. Y.,
runs in a valley recognized as pre-glacial. The horizon-
tal fault at the Falls has certainly no connection with a
terrace though the one by the bridge has some such rela-
tion and to a post-glacial terrace at that. However, they
appear to be so in accord with the rest of thO evidence
concerning the diastrophic history of the region that it
hardly seems necessary to call in outside evidence for
their explanation.
	A second type of faulting as shown in the shale mem-

246

bers of the Hamilton is a compound or slice fault devel-
oped on the south side of Stony Point some 25 miles down
Cayuga Lake. At this point a hard layer of limy shale,
much more compact and resisting than the surrounding
shale is sharply turned up at a 100 angle with dip to the
south. The faults occur just at the start of this high dip,
the greatest measured. For 200' along the shore south of
the point, the N 120 W joints show horizontal faulting
with displacement of 1" to 112" of the joints of the E-W
system. The movement has pushed forward each succes-
sive block between two faults from west to east. That is,
the western part of the zone has not moved so far north
as the eastern part. The N-S joints dip west a few
degrees from the vertical but the angle was not measured.
It probably does not exceed three degrees as other joints
of the region which are not vertical show a dip very gen-
erally around 20. The faulted area covers the entire
width of the shore as exposed at this point and may exist
over an even greater width and length. The rocks of the
whole point and near to it are broken up by an excessive
number of si~bsidiary joints at all angles and often much
curved.

	Mr. W. H. Bucher published an article on "The
Mechanical Interpretation of Joints," in the Journal of
Geology for December of 1920. To one not acquainted
with the laws of mechanics the "interpretations~~ sound
quite convincing. His main thesis is, that in brittle sub-
stances the lines of greatest pressure will bisect the acute
angle formed by the shearing planes. He then applies
this law to three areas, one of which happens to be the
Cayuga Lake region. Not being acquainted in person
with the area, he relies for his calculations upon the data
given in an article by Miss Sheldon.9 His conclusions,
put into figures, being that the compressive forces, must
lie in a general N 350 E direction since this line must
bisect the angle between the two major joint systems of
the region, the average of the greater part of whose
angles will run at about N 740 E and N 50 W. This appli-
cation is here made to only the northern part of the area
which he discusses, but the results as stated are only a few

Sheldon, P.; Some Observations and Experiments on Joint Planes, 
Jour. Geol., vol. 20, No. 1, 1912.

247

degrees at variance with those for the larger area. As
proof of the applicability of his theory, he cites the pres-
ence of buckling as shown by a raised area in the northeast
part of the Catatonk quadrangle, and of a depression in
the central portion, near Jenksville. These are unques-
tionably present and quite possibly bear some relation to
the joints of the region, but they are not the only domes
and depressions which occur in the two quadrangles.10
Following the axis of the Watkins anticline as he sug-
gests, the Portage-Chemung contact, starting at about
1520' near the western boundary of the map, dips toward
Seneca Lake valley, and at Texas Hollow, to the east, has
risen to an elevation of 1480' whence the beds continue
horizontal to a point two miles southwest of Enfield, the
last exposure west of Cayuga valley, along this line. To
the north near Reynoldsville, on the crest of the Firtree
anticline this contact is 1600' as it is on the crest of the
Alpine anticline to the south and near Cayuga (Corrected to Cayuta)  L. The
first contact shown east of Cayuga valley following the
axis of the Watkins anticline as stated, is at Pleasant Hill,
six miles east of Ithaca and 14 miles east of Enfield where
the contact is 1720' or 240' above the contact at Enfteld.
Were the secondary synclinal fold in which Cayuta (corrected to Cayuga)  Lake
lies disregarded, there would be in this 14 miles a rise of
but 17' to the mile, whereas the rise to the north from the
depression at Jenksville mentioned by him is over 43' per
mile for 16 miles. The average of a number of southerly
dips north of the big bend of Cayuga Lake is about 45' per
mile, steeper dips developing as the datum plane of the
Tully limestone is followed north. Owing to the lack of
geological and especially structural knowledge of the area
to the north of the Watkins and Catatonk quadrangles, it
seems hardly possible to form a very reliable opinion of a
district so near to the unknown. Work to the north along
Cayuga Lake this past autumn, together with observations
of the mapped quadrangles, would seem to indicate that
the greater southerly dips, even discounting what is due
to the folding process, are entitled to equal, if not greater,

10 In a personal communication Mr. Eucher claims two sets of 
movements, that producing the joints and buckling being prior to the one 
which developed the major folds and their accompanying faults. The 
horizontal fracture planes he thinks may have originated during the first 
activities, only the movement taking place later.

248

significance than the pitch of the anticlines and synclines
and dips associated with a buckling process.

	Judging from field evidence and acquaintance with the
region, Mr. Bucher `s results imply a large latitude in the
angle of his bisectrix as well as the presence of some
modifying or secondary forces not yet understood. Nev-
ertheless the old idea of compressive forces acting from
the southeast will apparently have to be revised in favor
of a southwesterly direction. This is probably due to the
lack of recognition accorded the short east-west segment
and may be considered a local exception. Here, two
entirely independent arguments, aiming to demonstrate
different ideas, have developed conclusions more closely
allied with each other than is either one with the usual
conception of the movements of Appalachian folding.

	Ithaca, N. Y.