Compliments of 
the author. 
Washington,D. C. St. Peter's Sandstone. 
115 
Reprint from the Journal of The Cincinnati Society of Natural History, July, 1894. 
THE ST. PETER'S SANDSTONE. 
By Joseph F. James, M. Sc., F. G. S. A., Etc. 
INTRODUCTION. 
In all geological investigations, rocks of any particular 
formation are noticed long previous to their differentiation 
under a distinct name. The reason is that observations are 
made by explorers and travelers in different portions of the 
country before the adoption of any definite system of nomen- 
clature, and facts are recorded without a reference of the 
rocks to any special horizon. Therefore, although the St. 
Peter's sandstone is unknown as a formation with a distinct 
name in the geological column prior to 1847, references were 
made to it years previously. 
The first reference to, and description of, rocks now known 
as the St. Peter's sandstone is given by Captain Jonathan 
Carver, in his travels through the interior parts of North 
America, in 1766-67-68. In this volume (p. 63) he gives an 
account of a cave visited by him, now known by the name of 
Carver's Cave. It is situated about thirty miles below 
the fi'alls of St. Anthony, and is an excavation in the St. 
Peter's sandstone. Carver found the stone so soft that it 
could be cut with a knife, and the walls of the cave were 
carved with Indian hieroglyphics. He also states that a little 
way from the mouth of the St. Peter's River is a hill com- 
posed entirely of white stone, the outer part of which crum- 
bles into heaps of sand through the action of the weather.* 
This, also, is St. Peter's sandstone. 
In 1817, Major Stephen H. Long visited the Falls of St. 
Anthony, and in his book he gives an account of the forma- 
tions observed by him in Minnesota. One of these was a 
white or yellowish sandstone, which crumbled so easily as to 
deserve the name of sandbank rather than that of sandstone. 
*Ibid, pp. ioo, ioi. 116 
Cincinnati Society of Natural History. 
It is stated to underlie the limestone that forms the brink of 
the Falls. " It is of various depths, from ten to seventy-five 
feet."* 
In 1820, H. R. Schoolcraft was sent by the general govern- 
ment on an expedition to the sources of the Mississippi 
River, and he submitted a report of his observations in 1821. 
This was republished in 1855,! and in this volume he refers 
to the geological features of St. Anthony's Falls, where the 
river is precipitated, at one leap, over " strata of white sand- 
stone, overlaid by the metalliferous limestone. * * This sand- 
stone is composed of grains of pure and nearly limpid quartz, 
held together by the cohesion of aggregation. If my obser- 
vations were well taken it embraces, sparingly, orbicular 
masses of hornblende. It is horizontal, and constitutes, in 
some places, walls of stratification, which are remarkable for 
their whiteness and purity."+ This is, undoubtedly, the St. 
Peter's sandstone. 
In 1824, Professor Keating || gave a section of the strata as 
observed by him at Fort Snelling. In this a sandstone is 
mentioned as occurring beneath from twenty-five to thirty 
feet of limestone, and which constituted the principal mass of 
the bluff. He says : " This is friable, but every fragment, 
examined with care, seems to be a regular crystal." Keating- 
inclined to the opinion that it must have been a chemical pre- 
cipitate, and not a mere mechanical deposit. He says: 
" The process of its formation may have been a rapid one, 
such as is obtained in the manufacture of fine salt; and to 
this may be attributed the circumstance of its fine texture. 
The color is white, sometimes a little grayish, when it resem- 
bles the finer varieties of Muscovado sugar."§ 
In the report of Dr. John Locke, made in 1839,* in describ- 
Voyage iu a six-oared skiff to the Falls of St. Anthony, in 1817. Minn. Hist. 
Soc. Coll., Vol. II, p. 36 (pub. i860). 
t Summary narrative of an exploring expedition to the sources of the Missis- 
sippi. Appendix VII, pp. 303-362. Philadelphia, 1855. 
t Ibid, p. 330. 
|| Narrative of an expedition to the source of the St. Peter's River, etc., per- 
formed in the year 1823, under command of Major Stephen H. Long. 2 vols, 1824. 
Quoted in Vol. I of Final Report of Geology of Minnesota, 1884, p. 35. 
If [Comparison of the geological formations of the lead regions of Iowa and 
Wisconsin, and the cliff formation of Ohio, Indiana, and Kentucky, with various 
sections.] Rept. of Geol. Expl. of part of Iowa, Wisconsin, and Illinois, by D. D. 
Owen, pp. 116-126. 26th Cong., 1st Sess , H. R. Ex. Doc., No 239, 1840. .Si. Peter's Sandstone. 
117 
ing a section as observed at Prairie du Chien, he notes the 
presence of a sandstone underlying a buff colored limestone 
and called "soft saccharoid sandstone." It is stated to be 
made up of sharp, angular fragments of quartz, scarcely 
cemented together. It may be white or colored, and when so 
colored it is often strongly cemented. It is compared to 
coarse, common, unrefined sugar, and, though it is difficult to 
break off a piece without its crumbling to pieces in the hand, 
yet, in places, it crops out extensively, and seems to stand 
the weather as well as other strata which are used for build- 
ing stone. It is here given a thickness of forty feet, although 
Dr. Locke says he did not see the base of the formation. In 
the section accompanying the paper this sandstone is repre- 
sented as lying between a blue limestone (now recognized as 
Trenton) and the Lower Magnesian limestone.* In the 
description of the strata from the Blue Mounds to the Wis- 
consin River, this sandstone is again referred to as the same 
as seen at Prairie du Chien. " It is remarkable for having 
its upper surface at an exact and even plane, very nearly 
level. In an excavated area, where several ravines meet in 
the same valley, and with the eye at any point of the upper 
surface of this sandstone, all other points appear at the same 
plane, like an emptied lake, leaving a line of ice to mark its 
original height; even where the rock is covered by earth, 
the vegetation changes so abruptly in sort and color, at the 
surface of the sandstone, that the line may still be distinctly 
traced. "t 
On November 2, 1842, a paper by Dr. D. I). Owen+ was read 
before the Geological Society of London. It was read in 
April of the following year before the American Association 
of Naturalists and Geologists. Dr. Owen notices the pres- 
ence of a sandstone underlying conformably a blue fossilifer-. 
ous limestone. The sandstone is " sometimes of a deep red 
and sometimes of a white color, and resembling loaf sugar. 
Beneath this succeeds a magnesian limestone." He also says 
he has never found any fossils in the sandstones.|| This for- 
*Ibid, p. 123. 
t Ibid, p. 124. 
tOn the Geology of the Western States of North America. Am. Jour. Sci., Vol. 
XLV., pp. 151-152, 163-165 ; Quart. Jour. Geol. Soc. London, Vol. II, pp. 443-447, 1846. 
|| Ibid, p. 446. 118 
Cincinnati Society of Natural History. 
mation he afterward described under the name of St. Peter's 
sandstone. 
The first mention of the term St. Peter's, as applied to a 
geological formation, was made by Dr. D. D. Owen, in 1847.* 
After referring to the formations of the Upper Mississippi, 
it is stated that in some high situations, as near Lake St. 
Croix, the strata are surmounted " by soft white sandstone, 
capped with shell limestones, such as form the upper portions 
of the hills on the Wisconsin River, near Prairie du Chien, 
and constitute the whole of the escarpment of the St. Peter's 
falls, as well as the bluffs on both sides of the Mississippi, 
from thence to Carver's Cave and St. Pauls; and, therefore, 
sometimes alluded to by us under the local name of the St. 
Peter's formation."f Thus, no specific description of the 
formation is given in this, the first place of reference. That 
this is the formation in question, however, there can be no 
doubt, inasmuch as in the following year the strata were 
described, and in 1852 the name St. Peter's was definitely 
adopted. 
In the report of Dr. Owen, published in 1848,+ this forma- 
tion is called " F. 2 c." It is superimposed on the Lower 
Magnesian limestone, and is the rock which forms the base of 
the bluffs at St. Peter's, and likewise the lower nineteen feet 
of the Falls of St. Anthony, It is said to be remarkable for 
its whiteness, and to be made up of grains of limpid and 
colorless quartz. " It appears to be destitute of organic 
remains; at least none have as yet come to light. In the 
absence of these, it is difficult to say whether it ought to be 
considered as the terminating member of F. 2, or the inferior 
member of F. 3. Since, however, it appears to have been 
produced by a repetition of sedimentary action, similar to 
that which occurred just at the commencement of F. 2, I 
have thought it best to place it, for the present, as the ter- 
minating mass of that formation." || In the series of sections 
* Preliminary report of Progress of the Geological Survey of Wisconsin and 
Iowa up to October nth, 1847. U. S. Land Office Report for 1847, pp, 160-173. 30th 
Cong., 1st Sess., S. Ex. Doc., No. 2. 
t Ibid, p. 169. 
JOn a geological reconnoissance of the Chippewa land district of Wisconsin, 
and the northern part of Iowa, 1848. 
|| Ibid, p. 28. St. Peter's Sandstone. 
119 
accompanying the report, the sandstone is represented as " F. 
2? c," and as occupying a position beneath the lower shell 
limestone, and above the Lower Magnesian limestone. 
In 1852, Dr. D. D. Owen* described the St. Peter's sand- 
stone in almost the identical language used in the report of 
1848, referred to above. 
Having in this brief historical review given an account of 
the observations made upon the rocks previous to its receiv- 
ing the name which it now bears, let us examine the forma- 
tion somewhat more minutely as to its distribution, lithologi- 
cal characters, stratigraphic position and fossils. 
DISTRIBUTION. 
The St. Peter's sandstone is confined to a limited district in 
the upper Mississippi valley. It is found in the States of 
Minnesota, Wisconsin, Illinois, Iowa and Missouri, and possi- 
bly in the northern peninsula of Michigan. 
In Minnesota it outcrops in an irregular line in the south- 
eastern part of the State, extending north-west from the 
southern boundary to above Minneapolis, and south-west 
again to Martin and Jackson counties. 
In Wisconsin it is found in a narrow strip running from 
the Menominee River, at the north-eastern boundary, to the 
southern boundary, occurring in patches wherever the rivers 
have cut into the superincumbent formations to a depth 
sufficient to reach it. It also outcrops to a limited extent in 
St. Croix and Pierce counties in the north-western corner. 
In Illinois it is found in two isolated patches; one of these 
is on Rock River, near Grand de Tour; the other on the 
Illinois River, in La Salle County. It also probably under- 
lies a part of the State, being only known by deep-well 
borings. 
In Iowa it is found exposed only in the north-east corner, 
though its presence has been revealed in other localities by 
deep wells at from 1,100 to 1,200 feet beneath the surface. 
!>[Protozoic rocks in the northwest.] Geol. Survey Wisconsin, Iowa and Minne- 
sota ; and incidentally of a portion of Nebraska Territory. Philadelphia, 1852, pp. 
69-71. 120 
Cincinnati Society of Natural History. 
In Missouri the " Saccharoidal sandstone " has been correla- 
ted with the St. Peter's. It is known in several places along the 
Mississippi River. There has been considerable dispute as to 
the exact age of the Saccharoidal sandstone, but the latest 
examination of it by Dr. F. L. Nason* led to the conclusion 
that the division which has been made of first, or saccha- 
roidal, second and third sandstones, and first, second, third 
and fourth magnesian limestones can not be maintained. He 
says the evidence is not sufficient to' make more than one 
sandstone and one limestone formation. For the first he 
proposed the name of Roubidoux sandstone, and for the 
second the name of Gasconade limestone. It seems probable 
that the strata that have been referred to the St. Peter's in 
Missouri are Cambrain rather than Silurian. 
Finally, in Michigan, it apparently occurs in a narrow strip 
running from the Menominee River to the Sault Ste. Marie, 
the Rake Superior sandstone having been considered by some 
authors to belong to this period also. 
LITHOLOGICAL CHARACTERS. 
In all its typical outcrops the St. Peter's sandstone presents 
the same characteristics, being a friable, coarse-grained sand- 
stone, the grains cohering but slightly, except when per- 
meated by carbonate of lime or various oxides of iron. It 
then becomes hard and indurated. In color it varies greatly, 
being white, red, brown, yellow, gray, pink, green, lilac, and 
also being frequently banded in an irregular manner. It 
occasionally shows stratification planes, and ebb and flow 
structure, and rarely, ripple marks. In thickness it varies 
from a thin layer to a stratum over two hundred feet thick, 
though the latter is infrequent. Its peculiar character and 
the supposed entire absence of organic remains have caused 
it to be regarded by some authors as a chemical precipitate 
rather than as of mechanical origin. We have already seen 
that Keating, in 1824, considered it to be the former. The 
same idea was advanced in 1858 by Prof. J. D. Whitney,t 
*Geol. Sur. of Missouri, Vol. Ill, Dec., 1892. 
•(•Geological Sur. Iowa, Vol. I, Part 1, 1858, p. 341. S/. Peter's Sandstone. 
121 
who says that if this quantity of quartzose sand be the 
result of the mechanical attrition of azoic rocks, that 
it is difficult to understand the absence of detritus which 
would come from the destruction of schistose, feldspathic and 
trappean rocks which make up so large a portion of the azoic 
series. "The uniform size of the grains of which the sand- 
stone is composed, and the tendency to the development of 
crystalline facets in them, are additional facts which suggest 
the idea of chemical precipitation rather than of mechanical 
accumulation." 
The later discovery of fossils, although in limited numbers, 
has now caused it to be generally regarded as of mechanical 
origin. Upon this point Prof. Chamberlin* says that " the 
existence of the remains of marine life demonstrates that the 
fossiliferous portions at least are submarine deposits, while 
the well-rounded character of the grains, the ebb and flow 
structure, the shaly laminations, the conglomeritic portions, 
and its relations to the adjacent formations, leave no doubt 
that it belongs to the common class of oceanic sand deposits." 
ECONOMIC VALUE. 
The purity of the sandstone and its peculiar character have 
rendered it of value in the manufacture of glass in certain 
localities. The fact of its being generally overlain by a 
heavy stratum of limestone, has given it even more value to 
mankind, inasmuch as it is the cause of many waterfalls which 
are utilized for manufacturing purposes. It is the cause, for 
example, of St. Anthony's Falls, which has been to Minne- 
apolis a source of immense wealth. Prof. N. H. Winchell, in 
the first annual report of the Geological and Natural History 
Survey of Minnesota for 1872 (1873), page 92, says, that at 
present the "sandstone is not known to be used for any purpose 
within the State except for mortar for the local markets and 
as an engraving board for idle boys. Sometimes beer vaults 
are made in it along the river bluffs, and sewers for the drain- 
age of the cities of St. Paul and Minneapolis are excavated 
through it, the overlying limestone affording a secure roof.'' 
*Geol. of Wisconsin, Vol. II, 1878, p. 288. 122 
Cincinnati Society of Natural History. 
The base of the formation has been but seldom observed. 
Professor Winchell has recorded one observation upon it. 
This was in Nicollet County, Minnesota, and he says about 
two feet of white sandstone with a thin strip of shale overlay 
the Magnesian limestone below. It frequently retains its 
arenaceous character to its contact with the underlying rock.* 
Professor Hall has also noticed the junction, and says that 
sometimes there is a finely laminated clay with stripes of 
green,f and the sandstone is often similarly colored. The 
irregular surface of the Lower Magnesian limestone is fre- 
quently the cause of great variations in its thickness, as it fills 
up hollows and covers ridges which exist there. In Missouri 
this feature is especially remarkable. Mention is made of one 
locality where the formation thickens so rapidly as to present 
the appearance of a dyke cutting off the sandstone both 
above and below.+ In another place it forms a bed 240 feet 
long and sixty feet deep, filling a cavity in the limestone of 
this extent.|| 
In 1877, Professor Chamberlin refers to the St. Peter's sand- 
stone in eastern Wisconsin.$ He notes the unequal deposition 
of the sandstone on the Lower Magnesian limestone, stating 
that, instead of being of uniform thickness, as has been often 
asserted, it ranges from a thickness of 212 feet down to a 
single layer of sand grains. It sometimes varies from 100 
feet to zero in the course of a quarter of a mile. Instances 
are known of its entire disappearance, and the consequent 
resting of the Trenton limestone on the upper surface of the 
Lower Magnesian, while in the near vicinity a thickness of 
from fifty-four to 100 feet has been noted. 
THE BASE. 
THE TOP. 
Its junction with the overlying limestone has been more 
frequently observed. Sometimes the transition is abrupt, but 
annual report of the Geological and Natural History Survey of Minne- 
sota, for 1874, 1875, P- I32-. 
fReport on the Geology of Wisconsin, Vol. I, 1862, p. 29. 
JFirst and Second Annual Reports of Geological Survey of Missouri, 1855, p. 119. 
(Reports on the Geological Survey of Missouri, 1855-1871, 1873, pp. 142-143. 
of Wisconsin. Survey of 1873-1877. Vol. 2, pp. 285-290. 5/. Peter's Sandstone. 
123 
again there occur certain transition beds, of which it is diffi- 
cult to say whether they should be referred to one or the other 
formation. 
At Seward's quarry, about two miles from Ripon, Wisconsin, 
the junction between the St. Peter's and the overlying Tren- 
ton is well shown. It is here a very friable sandstone, varying 
in color from yellow to brown. The upper layers, just beneath 
the limestone, contain concretions or nodules varying in size 
from half an inch to six inches in diameter. The sand is 
irregularly stratified. In places it is white, but it is generally 
more or less stained. The separation between the limestone 
and the sandstone is distinct. The lower layers of the former 
contain more or less sand, and are in thin courses one-half to 
one and one-half inches thick. Above they become heavier, 
from four to six inches, but do not seem to be fossiliferous. 
About fifteen feet of the sandstone is exposed. A short dis- 
tance from this quarry is another exposure of the sandstone 
about twenty feet high. No limestone capping is present. 
The sand is often banded with red, while white and brown 
streaks sometimes alternate. It contains a few concretions 
near the top, below the junction with the limestone. 
At Mitchell's Glen, about four miles from Ripon and a mile 
from Green Lake, both the Trenton and the St. Peter's occur. 
The limestone is separated from the sandstone by transition 
beds about two feet thick. The upper one of these is quite 
sandy, as is also the lower, but the intermediate stratum, 
about a foot thick, is a solid, more or less calcareous mass. 
The St. Peter's proper is more or less friable, and white, 
yellow or brown in color, more generally one of the latter. 
The outer surface hardens on exposure, but in places it can 
be taken out with a spade. At one point in the Glen is a 
perpendicular fall of about fifty feet, at the bottom of which 
is a pool of water. The sandstone is here exposed in vertical 
walls on either side of the Glen to a height of seventy feet, 
capped by layers of Trenton limestone. The bedding of the 
sandstone is very irregular, dipping at various angles and in 
different directions. Numerous large springs of clear, cold 
water gush out from the sandstone walls. They probably 
mark the approximate place of junction with the Lower 
Magnesian. No fossils were observed by the writer. 124 
Cincinnati Society of Natural History'. 
At another point, also near Ripon, and the evident base of 
the Trenton, there is an intimate mixture of sandstone and 
calcareous material. In this occur large specimens of Ortho- 
ceras, which are of Trenton rather than of St. Peter's age. 
At Pomeroy's quarry, near River Falls, Wisconsin, at the 
top of a high hill, is an exposure of the Trenton limestone in 
heavy layers, and containing quantities of brachiopods. Be- 
neath this exposure is an outcrop of the St. Peter's, with a 
vertical height of about fourteen feet. The sand is dazzlingly 
white, easily disintegrating on exposure. It forms a con- 
spicuous feature in the landscape, the white line of outcrop 
appearing in numerous places along the face of the hill. No 
fossils were observed. 
On the bluffs east of Prairie du Chien the sandstone occurs 
above the Lower Magnesian limestone. It is mostly covered, 
and has an estimated thickness of eighty feet. In the bed of 
a stream that comes down the hill, several gigantic steps have 
been formed, each from five to eight feet high and with 
" treads " two or three feet wide. No fossils were observed. 
Professor Chamberlin has also noted passage bed as seen in 
Rock County, Wisconsin. He says "At several points in 
Rock County the passage of the St. Peter's to the formation 
above is attended by an alteration of sandstone and calcareous 
rock. The sandstone just below the calcareous bed is marked 
with fucoidal impressions, and the base of the calcareous 
layer contains abundant Scolithus tubes. The calcareous bed 
is of a greenish-gray cast, containing a large percentage of 
insoluble, argillo-arenaceous material, in addition to the 
evident quartzose grains that are more or less freely scattered 
through portions of it. This has not been observed to attain 
a thickness of more than four or five feet. The upper 
portion is usually shaly, and appears at some points to have 
been eroded before the deposition of the stratum of sandstone 
above. This latter is thin and mixed with argillaceous 
material on which sometimes supervenes a thin seam of car- 
bonaceous matter followed by the fossiliferous Trenton lime- 
stone. At the most northern point at which the junction was 
seen, the sand mingles freely with the calcareous layers of 
the Trenton, for several feet above their base. At most other 
points the usual abrupt transition was observed."* 
'■'Geol. of Wisconsin, Vol. II, p. 287. 57. Peter's Sandstone. 
125 
It is also discussed by Professor Swezy, who mentions* the 
occurrence of the St. Peter's sandstone at Beloit, immediately 
beneath the Trenton. The author says: " Between the St. 
Peter's sandstone and the Trenton limestone are eight feet, or 
perhaps more, of transitional layers; they include, at the 
bottom, a foot or so of sandstone, more coarse and impure 
than is usual with the St. Peter's; above this five feet of 
impure limestone and shale, and at the top two feet more of 
coarse sandstone." Above this series comes the typical Tren- 
ton limestone. In a diagram, presented on page 199, these 
transitional layers are not referred to either the St. Peter's or 
the Trenton. 
Another excellent exposure, showing transition beds be- 
tween the Trenton and St. Peter's, occurs at Fountain, Minn. 
This was first described by Prof. N. H. Winchell, in 1876.! 
His section is as follows : 
SECTION NEAR FOUNTAIN J QUARRY OF JOSEPH TAYLOR. 
FT. 
No. i. Green shale mixed with fragments of limestone 
that are eminently fossiliferous, seen, 3 
No. 2. Limestone, of a bluish-gray color, in beds from 
four to six inches thick, free from shale, though the layers 
are sometimes thinly separated by shaly partings, 10 
No. 3. Arenaceous and ferruginous shale, alternating 
horizontally with firmly cemented patches of sandstone, - 2 
No. 4. Massive coarse sand ; white, except where iron- 
stained, containing irony quartzite pebbles, and fragile re- 
mains of bivalves, 6 
No. 5. Green shale, with some arenaceous and calcare- 
ous laminations, 3 
No. 6. Cemented sandstone, the cemeift being shale and 
lime, forming, where the bluff is weathered, the floor of a 
bench, 1 
No. 7. White sand, in beds that are about one foot thick 
and horizontal 6 
No. 8. A course in the sandstone more firmly cemented, 
forming another table, but less persistent than No. 6, . . . 1 
No. 8 [9]. Massive sandstone, in some places showing an 
oblique lamination, seen, 6 
Total, 38 
41 On some points in the geology of the region about Beloit. Wisconsin Acad. 
Sci. Trans., Vol. V, p. 194. 
+ Fourth Rept. Geol. and Nat. Hist. Sur. Minn., for 1875, 1876, pp. 40-42. 126 
Cincinnati Society of Natural History. 
A species of Lingulepis is found in No. 4 of the foregoing 
section. Prof. W. says: "The remains are exceedingly 
fragile, and as the grains of sand in which they are embraced 
are feebly cemented together, it is nearly impossible to trans- 
port, or even to handle them without their falling to pieces. 
These fragments, for no entire specimens were obtained, are 
arranged promiscuously in the coarse sand, and are all con- 
fined within three feet of the top of No. 4. They seem to 
have suffered the attrition and friction incident to coarse sed- 
imentary transportation. They dispel the idea, which has 
been suggested, of the possible chemical origin of the St. 
Peter's sandstone, as an oceanic precipitate.'' 
This same locality was visited by the writer in 1889, and 
the following section was observed : 
FT. 
No. 1. Trenton limestone in thin courses, 
No. 2. Layers of coarse-grained, hard sandstone, formed 
of grains of rounded quartz, of nearly uniform size, with 
occasional fragments of Linguloid shells, 1 
No. 3. Loose sand, with yellow and brown streaks and 
greenish spots, 6 
No. 4. Greenish shale and sandstone, mostly shale, . . 5 
The upper portion of this bed is a white sandstone, 
formed of rounded grains of quartz, cemented by carbonate 
of lime, and containing fragments of fossils. The inter- 
stices of the sandstone are filled with fine particles of sand. 
Below this the shale is a mixture of clay, lime, and sand, 
the former green, the latter wdiite, and formed of rounded 
quartz grains. The green shale contains what appear to be 
worm burrows (Planolites), and fragments of Lingulepis 
mor sen sis Winchell. 
No. 5. White sandstone of St. Peter's covered, - 
Total observed, • . . . 12 
About half a mile further down the railroad another ex- 
posure occurs. Here the typical St. Peter's sandstone is well 
exposed, and it is overlaid by the same succession of shale, 
loose sand, hard sandstone and limestone, as that in the pre- 
vious section. In the upper portion of the shale are certain 
iron-stained layers, in which brachiopods of the genus Orthis 
are found. These are also seen in the sandstone, together 
with fragments and impressions of Lingulepis -mor sensis. 5/. Peter's Sandstone. 
127 
In the twelve feet of sand and shale given in the above 
section, we have transition beds between the true Trenton 
limestone and the typical St. Peter's sandstone below. It 
would appear that after the deposition of the white sandstone 
there came a period of muddy seas, during which the green- 
ish shales were laid down. Then followed a period of eleva- 
tion to near the surface, when the loose sand and the harder 
beds below were deposited. The latter were probably 
cemented together by lime from the layers of limestone 
above, which were in their turn laid down in a deepening 
sea, that soon swarmed with life. 
In a late paper by Messrs. Hall and Sardeson* a similar 
conclusion is reached. These authors say that they nowhere 
found in Minnesota any indication of an uncomformity be- 
tween the Trenton and St. Peter's. "The transition zone of 
a green shaly calcareous sandstone shows the steady oncom- 
ing of that Lower Silurian sea which, if it did not submerge 
the whole Northwest, at least extended so far that the dry 
land was reduced to islands, or narrow peninsular stretches of 
very uncertain connection with a mainland lying somewhere." 
STRATIGRAPHIC POSITION. 
The position of the formation in the stratigraphical col- 
umn is unequivocal. It lies between the Lower Magnesian 
limestone and the Trenton limestone, but its limited area in 
the country, and its practical isolation from eastern localities, 
renders its correlation with formations elsewhere a matter of 
difficulty. In addition to this the almost total absence of 
fossils adds to the perplexity, as it is by means of the organic 
forms that rocks are most accurately correlated. The only 
point where direct stratigraphic continuity with any eastern 
North American formation can be looked for is on the Cana- 
dian side of the Sault Ste. Marie. Its presence here is shown 
on the geological map of Canada by Hall and Logan,f though 
it is present to only a limited extent. It does not occur 
again, in outcrop at least, until the Ottawa River is reached. 
-'Bull. Geol. Soc. America, Vol. Ill, p. 355. 
f Atlas accompanying Geology of Canada from commencement to 1863. 1865. 128 
Cincinnati Society of Natural History. 
some 350 miles to the eastward. Even in Canada and the 
eastern States, where it is known as the Chazy, it occupies 
scattered patches, which are limited in area. On the map 
referred to above, the sandstone on the south shore of Lake 
Superior, and the outcrops of St. Peter's in Wisconsin and 
Minnesota, are colored as Chazy ; and in another map in the 
same atlas, showing the distribution of the Huronian rocks, 
by Sir W. E. Logan, the distribution of the sandstone is 
given in more detail, and it is designated in the legend as 
" Chazy (St. Peter's Sandstone)." 
The reference of the St. Peter's to the horizon of the Chazy 
has been made by various writers, solely, it would appear, 
upon stratigraphic evidence. Hall, in 1863,* considered it as 
the equivalent of the Chazy. He says: " So long since as 
1845, I had myself observed that the sandstones of the St. 
Mary's River come out from beneath the Black River and 
Birdseye limestones; but the Calciferous sandstone was no- 
where visible in the immediate neighborhood. The later and 
more complete investigations of the Canada Geological Sur- 
vey have proved the absence of the Calciferous sandstone, 
and of the Potsdam sandstone, on the north shore of Lake 
Huron ; and, also, that this sandstone of St. Mary's River 
(which is now regarded as identical with that of the south 
shore of Lake Superior), rises from beneath the Black River 
and Birdseye limestone, and there is no evidence of the Cal- 
ciferous sandstone in that region. It is the opinion of Sir 
William Logan, that this sandstone represents the Upper 
sandstone, or fills the place of the Chazy formation in the 
East, the limestone being absent; and that it is this arena- 
ceous deposit, greatly augmented, which gives the sandstone 
formation of the south shore of Lake Superior (Geology of 
Canada, 1863, pp. 83-86)." 
After giving the sequence of the formations as found in the 
Mississippi valley, as Buff-limestone-Birdseye and Black 
River; St. Peter's sandstone; Lower Magnesian limestone, 
he says: "In assigning a position to the sandstone of the 
south shore of Lake Superior, to the south and east of 
Keweena point, from the evidence before us, and in the 
absence of any fossils which may aid the decision, we are 
* Sixteenth Ann. Rept. N. Y. State Cab. Nat. Hist., pp. 214-215. S7. Peter's Sandstone. 
129 
forced to conclude that this formation is a greatly augmented 
development of the St. Peter's sandstone; or, that the Lower 
Magnesian limestone ("Calciferous sandrock'') has thinned 
out, so as to leave the St. Peter's sandstone and the Potsdam 
below (as developed in the Mississippi valley) to go on as one 
mass to the northward." 
"It is scarcely possible to suppose that the lower sandstone 
of the upper Mississippi Valley has not, at some time or in 
some form extended as far as Lake Superior; but it is far 
from being proved that the sandstone now so largely developed 
on the south shore is that sandstone, as we have shown. If 
this sandstone consist of both that above and that below the 
Calciferous, or of the St. Peter's and the Potsdam proper, then 
at some point we should expect to find a change of character, 
or nonconformity between the beds, to indicate the lapse of 
time in the deposition of the Lower Magnesian limestone of 
more southern localities; and this view is sustained by the 
observed want of conformity between the sandstone and 
Magnesian limestone near Dead River just cited."* 
The question is here left in an unsatisfactory condition; 
but if the later conclusions,f that the Lake Superior sand- 
stones are Potsdam or pre-Potsdam in age be sustained, it is 
probable that the St. Peter's formation will be confined to a 
narrow strip through the northern peninsula from the 
Menoninee to St. Mary's River. 
Hall asserted the same again in 1869,+ as did also Logan|| 
in the map of Canada in 1865. 
In referring to the sandstone east of Keweenaw Point, 
sometimes called the Eastern sandstone, Dr. Alex. 
considered it as the probable equivalent of the Calciferous 
and Chazy formations of New York. He says, in regard to 
the Lake Superior sandstone as a whole : " The portion west 
of the Point is thought by some to be of the same age 
[Calciferous and Chazy], while others regard it as the equiva- 
,;'Ibid, pp. 215-216. 
flrving, R. D. : Copper-bearing rocks of I,ake Superior. Monographs U. S 
Geological Survey, Vol. V, 1883. 
pAm. Phil. Soc. Trans., new ser., Vol. XIII, p. 329. 
||Atlas accompanying the Geology of Canada from the commencement to 1863. 
1865. 
of Topography, Climate and Geology of Michigan. Walling's Atlas 
of Michigan, 1873, p. 46. 130 
Cincinnati Society of Natural History. 
lent of the sandstones in Wisconsin and Minnesota, which are 
generally ranged in the horizon of the Potsdam of New York. 
As the uplift of Keweenaw Point has tilted the sandstones on 
the west, while those on the east have retained their horizon- 
tality, there is reason for supposing that the eastern strata are 
of more recent origin. It may, nevertheless, be true that the 
sandstones on both sides of the Point are of the same age, 
though those on the eastern side were not permanently tilted 
by the convulsion which upheaved the others. As we find 
apparently superincumbent strata, which answer to the Cal- 
ciferous, we shall continue to parallelize the Lake Superior 
sandstone, presumptively, with the Potsdam." 
Dr. Rominger, in 1873,f also considers the Chazy and Cal- 
ciferous under one head. In his description he says: " Belowr 
the well-characterized Trenton strata, and reposing on the 
Lake Superior sandstones, we find over the whole extent of 
the Peninsula a series of calcareous or arenaceo-calcarei us 
beds which hold the place of the Chazy limestone and the 
calciferous formation of the Eastern States. We can not dis- 
tinguish two different formations with different faunas in the 
West, where all the fossils ever found are three or four 
species of shells, and those generally in imperfect condition. 
Bat we can see a plainly expressed typical similarity between 
the fossils of the eastern and western localities. Also the 
lithological characters of the compared rocks are in perfect 
general correspondence, so that we can safely consider our 
western strata as the equivalents of the two named groups 
of the New York system. The greatest observed thickness 
of the formation within the district is near* 100 feet, but 
usually it is not found in so large a development." Worthen, 
in 1866,+ considered the St. Peter's to form the upper portion 
of the Calciferous series of New York, while in Broad- 
head|| makes the Saccharoidal sandstone equal to the St. 
Peter's and also to the Calciferous. 
In 1883 Prof. gave a resume of the knowledge 
of the formation. It is stated to repose on the billowy sur- 
-Ibid, pp. 43-44. 
jMichigan Geological Survey. Palaeozoic Rocks, 1873, p. 71. 
Survey of Illinois, Vol. I, 1866, p. 149. 
[[Report of the Geological Survey of Missouri; field work, 1873-1874; 1874, 
chart oppo. p. 18, and p. 29. 
[{Geology of Wisconsin, Survey of 1873-1879, Vol. I, 1883, pp. 145-150. S'/. Peter's Sandstone. 
131 
face of the Lower Magnesian, and to be an almost pure quart- 
zose sandstone. The greatest thickness observed was 212 
feet, but its average is hardly over eighty. Traces of life are 
rare. The method of formation is considered due to me- 
chanical action, rather than to chemical solution. In dis- 
cussing its history it is stated that the sand was probably 
derived from the Archean nucleus or the Potsdam sandstone 
toward the north, which was then exposed above the surface, 
or at least subject to the mechanical action of the waves. 
The distribution is given, the Saccharoidal sandstone in 
Missouri and the Chazy limestone of New York being con- 
sidered its equivalents. He says: "We have felt somewhat 
inclined to refer its main deposition to the closing Calciferous 
or early Quebec, and to suppose that it was rewrought by 
the advancing sea in the Chazy or early Trenton epoch, the 
remainder of the interval between the Calciferous and the 
Trenton being unrepresented in our series, because the 
water had retired."* 
As known in New York, the Chazy formation is essentially 
a limestone, and therefore differs greatly in lithological 
features from the St. Peter's. But in Canada the limestone 
is associated with sandstones and shales. At Greenville the 
calcareous strata are succeeded by about fifty feet of whitish 
sandstone, in beds from two or three to twelve inches, inter- 
stratified with bands of green shale, holding great numbers 
of fucoids.t A sandstone, in beds of from four to twelve 
inches thick, interstratified with green arenaceous shales is 
found resting on the Laurentian, and immediately underlying 
the Trenton. This is found near the mouth of the Coldwater 
on Lake Huron. + 
The beds of sandstone here mentioned form, however, only 
a small portion of the formation, while in the west the cal- 
careous feature is almost entirely absent. This difference in 
lithological features, and the scarcity of fossils combined, has 
made it difficult to say positively, but the facts all point to 
the conclusion that in the St. Peter's sandstone we have the 
western equivalent of the Chazy limestone of the New York 
system. The correlation rests almost entirely upon the strati- 
graphic position. 
-Ibid, p. 150. 
tGeology of Canada, from the commencement to 1863. 1863, pp. 123-124. 
Jlbid, p. 192. 132 
Cincinnati Society of Natural History. 
FOSSILS. 
The organic remains found in the St. Peter's are but few. 
The following list is believed to include all that have been 
noticed as occurring. 
BRACHIOPODA. 
Lingulepis morsensis Winchell. Prof. N. H. Winchell, in 
1876, described this species as follows: "Shell conical or 
elongate-conical, with anterior angles rounded ; depressed ; 
the apical angle not seen perfect; the front margin gently 
convex ; sides nearly straight, but converging at an angle of 
about 26 degrees ; greatest width is near the front, and at a 
distance from the anterior margin of one third the greatest 
width. The surface is smooth and shining, marked with 
very fine concentric striae, visible especially in the anterior 
portion, and with more distant, dim undulations of growth. 
Entire length of the larger specimen seen about .85 inch; 
width, .52 inch; length of the smaller, .78 inch; width, .45 
inch. Color of the shell light brown, with spots of brown. 
The smaller specimen has flattened, or slightly concave 
margins, for nearly two-thirds the length from the apex. The 
species in general contour resembles Lingulepis briseis, of 
Billings (Palaeozoic Fossils, Vol. I, p. 48), but differs from it 
in not having its sides parallel."* 
This species is found at Fountain, Minnesota, in a sandy 
shale, in transition beds between the Trenton and the typical 
St. Peter's, and it is really questionable if it belong to the 
latter period. It has, however, been placed there by Winchell, 
and is therefore inserted here. 
Orthis sp. cf. testudinaria Dalman. A species of Orthis 
resembling in size and marking O. testudinaria, occurs in the 
sandstone and shale beds at Fountain, Minnesota, in associa- 
tion with Lingulepis morsensis. A similar form is found in 
the Trenton, which overlies the St. Peter's at Ripon, Wis- 
consin. 
'•Fourth Annual Report of the Geological and Natural History Survey of 
Minnesota for 1875. 1876, p. 41. St. Peter's Sandstone. 
133 
GASTEROPODA. 
Specimens of the genus Murchisonia are referred to by 
Meek as occurring in Monteau County, Missouri.* Crinoid 
columns were also found associated. 
Fragments of the internal casts of Straparollus and 
Chemnitzia were stated by Shumard to be found in the sand- 
stone in Ozark County, Missouri.f They were too imperfect 
for accurate determination. 
Maclurea (?). This is recorded by F. W. Sardesont as 
occurring in the St. Peter's formation, near St. Paul, Minne- 
sota, together with the species mentioned below. From the 
uncertainty felt in the identifications, it seems evident that 
the fossils are not in a very good state of preservation. Mr. 
Sardeson states that they occur about fifty feet below the top 
of the formation, and that " they are remarkably like species 
found in the lower part of the Trenton shales and in the 
Trenton limestone, which here rests conformably on the St. 
Peter sandstone." 
Murchisonia gracilis Hall. Murchisonia (?) tricarinata (?) 
Hall. 
LAMELLIBRANCHIATA. 
Cypricardites rectirostris Hall. Cypricardites, 2 sp. undeter. 
Modiolopsis ? (Mentioned by Sardeson.) 
ANNELIDA. 
Arenicolites ; Scolithus sp. A species of Arenicolites is 
referred to by Winchell|| as occurring in the sandstone at 
Faribault, in Rice County, Minnesota. He says: "The 
sandstone here is pitted with circular holes, such as have 
■•'First and Second Annual Reports of Geological Survey of Missouri, Part II, 
1855, P- 106. There is considerable doubt in regard to the exact position of all the 
fossils here recorded from Missouri. As already noted the Saccharoidal sandstone 
in which they are stated to occur, is referred by Nason to the Cambrian. 
fReports of the Geological Survey of Missouri, 1855-1871. 1873, p. 192. 
JFossils in the St. Peter Sandstone. Bull. Minn. Acad. Nat. Sci., Vol. Ill, p. 318. 
(Geological Survey of Minnesota. Volume I of the final report. 1884, pp. 656-657. 134 
Cincinnati Society of Natural History. 
been seen in a number of places in the State.* They are 
brought to view distinctly in the weathered and hardened 
surfaces, since the homogeneous sand on fresh fractures seems 
to constitute the entire rock, and no trace of these fossils is 
visible to the eye. They appear at this place on a lower bench, 
where the rock is hardened and reddened. They always run 
perpendicular, and can be traced to a depth of two and a half 
feet by the little furrows they cause on the face of the rock 
after the breaking and sliding down of masses of the bluff. 
This structure was first seen in this sandrock at the base of 
Dayton's bluff, at St. Paul, and was ascribed to Cretaceous 
lithodomous shells, but it is more likely to be due to some 
marine vegetable, or to worm-burrowing, of Cambrian age. 
By examining areas that have suffered different degrees of 
exposure, there can be traced a connection from the actually 
empty porous openings, through different degrees of exposure 
and induration, including a simple annular spottedness, to an 
innate internal structure in the mass of the rock itself. It 
would be the same as if a multitude of horse-tail rushes, or 
others, were growing in the bottom of the sea when the sand 
was accumulating, and became gradually buried under the 
sand, and then were imprisoned and fossilized, their presence 
only being evinced now by the cementation of the sand-grains 
about their exterior, or by a looseness of the same in their 
interior, thus not only forming a rude cast of each stem 
within the rock, but also providing for the more rapid erosion 
and removal of the grains that may have reached within their 
cases. The spots are only seen on upper surfaces, and if they 
be not due to imprisoned rushes or stems of some sort, or to 
worm-burrowing, they are at present inexplicable. They are 
generally from an eighth to a quarter of an inch in diameter." 
This species the present writer has proposed to call Sco- 
lithus minnesotensis:\ 
Similar tubes are noticed as occurring at Waterloo and 
Beloit, In Illinois, in LaSalle County,|| a pecul- 
iar feature of the sandstone is noticed. It is stated to contain 
*" They are conspicuous at Castle Rock, in Dakota County." 
fBull. Geol. Soc. America, Vol. Ill, 1891, p. 41. 
J Chamberlin, T. C. Geology of Wisconsin, Survey of 1873-77, Vol. II, 1877, p. 
288 ; also, Vol. I, 1883, p. 147. 
|| Geological Survey of Illinois, Vol. Ill, 1868, p. 280. St. Peter's Sandstone. 
135 
an infinite number of minute vertical holes, about the size of 
knitting needles. These are, perhaps, Scolithus tubes. In 
Missouri, there is found a sandstone formed of columns per- 
pendicular to the plane of deposit,* and these may also be 
Scolithus tubes. 
Planolites sp.-A species of Planotites was found by the 
writer in 1S89 at Fountain, Minnesota, in strata referred to 
the St. Peter's. It is associated with Lingulepis morsensis and 
Or this sp., already noted, but it has not been referred to any 
species. 
CEPHALOPODA. 
Orthoceras.-Fragments of Orthoceras, some of large size, 
are noted as occurring in this sandstone in Missouri.f One 
locality is in Maries County,! the specimen stated to be five 
and one-half inches in diameter, while other specimens thirty 
inches in diameter and ten feet long are found near the line 
between Gasconade and. Franklin Counties. In the roof of 
a cave near Marthasville, circular rings, supposed to be cross 
sections of Orthoceras, are noted.|| It is possible that these 
specimens really belong to the overlying Trenton. The 
writer has collected large specimens of the genus from the 
Trenton at Ripon, Wisconsin, in strata which were more 
arenaceous than calcareous, and which might readily have 
been referred to as a sandstone. 
The smalless of the number of species found in the sand- 
stone is thus seen. Their occasional presence, however, may 
be considered a proof that the formation is of mechanical ori- 
gin and not a chemical precipitate. 
* Reports on the Geological Survey of Missouri, 1855-1871. 1873, p. 55. 
t Swallow, G. C. Explanations of the Geological Map of Missouri, etc. Am. 
Asso. Adv. Sci. Proc., Vol. XI, Part 2, 1858, p. 17. 
t Reports of Geological Survey of Missouri, 1855-1871. 1873, p. 10. 
II Ibid, p. 55.