wet give a strong earthy odor and soapy feel. They readily soften into a blue clay when sufficiently exposed to the weather. These characters are always sufficient to readily distinguish the Hamilton shales from those of the Marcellus, Genesee and Portage. The Michigan representatives of these Hamilton beds seem to retain enough of these characters so that they may be separated from the St. Clair above and the Dundee beneath, even when their fossil contents cannot be procured. In southeastern Michigan and western Ontario there is a far greater development of limestone, at the expense of the shale, than in New York. Of the 95 feet in the Adrian well, according to the driller's log, 80 feet consisted of limestone, beneath which was 15 feet of black shale. In the Ann Arbor well referred to above, the 70 feet seems to have been largely limestone with the lower portions of the magnesian variety. Upon the St. Clair River the following section of the group occurs, as published by Lane in Vol. V, Michigan Geological Survey, Part II, (pp. 24-25).

Hard pyritiferous argillaceous limestone..

Shale, "soapstone"

"Top limestone," often gaseous

Shale, "top soapstone".

"Middle limestone"

Shale, "lower soapstone"

2 feet.

12 feet.

80 feet.

.150 feet.

4 feet.

65 feet.

"Bottom Limestone." (Corniferous.)

A somewhat similar series of beds occurs about Petrolea, Ontario, of which the following represents the average section in thousands. of wells:

Stiff blue boulder clay, drift....

100 feet.

"Upper limestone," with little black shale at

top .....

50 feet.

Bluish gray and drab shale, "soapstone" with
few hard layers.

120 feet.

"Middle limestone"

15 feet.

"Soapstone," with two or three hard beds.... 40 feet.
"Lower limestone" (Corniferous), giving oil at

45 and 135 feet.

The Traverse shales in Michigan are of the character ascribed to the typical Hamilton beds of New York, soft and bluish with a rather high percentage of lime carbonate. Certain layers may become much darkened, however, by bituminous matter. The limestones are typically bluish and argillaceous, but they may become dark

ened also. Fossils are exceedingly abundant in certain beds and beautifully preserved. The most common are various groups of the mollusca, corals, bryozoa and crinoids.

In the comparatively few wells sunk through the drift over the Traverse belt in Monroe County the description of the rock is very unsatisfactory. It is generally spoken of as hard or soft, as, we might expect from the sections above given. From Milan to the southwestern corner of Sec. 18, Milan township, several records of a very hard rock having been first encountered were obtained. In the village of Milan, according to one driller, the rock is an "exceedingly hard quartz rock," according to a second it is a "hard sandstone." Records of sandstone (probably dolomite) were obtained at the southwestern corner of Sec. 18 at Stephen Olds and J. C. Miller's. Two other records of a similar rock were obtained in the northwest and southwest quarters of Sec. 7, London township. At Charles Sanford's N. W. 1, S. W. 1, Sec. 9, Milan a very hard rock was struck at a depth of 112 feet. This was so hard that only a few inches could be drilled each day and it was entered but eleven feet. Another hard rock was reported at the N. E. 4, N. W 4 of this same section. At the place of Samuel McMullen, N. E. 4, N. E. 4, Sec. 17, a well was put down to a depth of 309 feet, rock being struck at 95 to 100 feet. The rock was said to be "shell limerock, more or less honey-combed," and yielded no water. Limestone was also struck at the S. W. 1, N. E. 1 Sec. 22, at Patrick Nolan's, in his well 171 feet deep. Rock was struck at a depth of 112 feet, and at 150 feet what seemed to be sandstone. A strong flow of gas was obtained at a depth of 145 feet, was lighted and burned all one night. Mr. B. R. Ford reports limestone at the S. W. 1, S. E. 1, Sec. 14, in his 110 foot well. "Soft white rock," which might refer to a much softened limestone, or to a highly calcareous marly shale, was struck at a depth of 96 feet at the place of E. E. Spink, Sec. 26, N. W. 4, N. W. 4. Two records. were obtained in this region which are much more suggestive of the typical Traverse shale. At a depth of 100 feet a "soapstone" was reached in the southeast quarter of Sec. 3, upon the place of Samuel Campbell. Thirty-five feet of this "blue soapy stuff" were entered. At Charles Campbell's N. W. 1, S. W. 1, Sec. 5, rock was reached at a depth of 142 to 143 feet. It is reported as a "soft mud rock, or soapstone." This was entered twenty feet when a "granite rock" was encountered. In the light of these facts it is difficult to predict the char

acter of the bed which will be found beneath the drift at any given point within this Traverse area. The problem is complicated not only by the number of beds, of such varying character, but also by the topography of the rock surface.

§ 16. Lithological history.

During the time required for the accumulation and deposition of the marine sediments which form the Traverse beds, broad open sea conditions were changing to those which characterize the off shore. These changes took place in consequence of oscillations in the seabottom, causing the shore line to recede or advance; or in the amount and distribution of the fine detritus from the land, carried by waves and currents. When the mud deposition prevailed beds of clay were formed, which required only great pressure to become a shale. The presence of bituminous matter in sufficient quantity to color the deposit black or brown, indicates that the conditions had thus early been established which gave to the St. Clair shale its bituminous character. Conditions were favorable also for numerous forms of life which secrete lime carbonate from the sea-water and as their remains were covered by the deposits they were preserved entire, or after disintegration were mingled with the mud. During long periods the amount of mud was greatly diminished and in this clear open sea bryozoa, corals and crinoids flourished in abundance. Their remains accumulated, were cemented together with a calcareous slime and after being subjećted to great pressure and some heat, were partially crystallized, forming the beds of limestone. If sandstone actually exists as is stated by the records given above, shore conditions must have prevailed temporarily and beds of sand accumulated, which were later cemented into compact rock, but probably there is no real sandstone.

D. Dundee Limestone.

17. Name and geological position.

By this local name the present State Geological Survey designates the great limestone belt, which in Michigan, Ohio, and Ontario. underlies the Traverse just described. It extends in all directions from southeastern Michigan and covers hundreds of thousands of square miles in the lake region, the Ohio and Mississippi valleys. It represents the upper member of a group of four, which are found well exposed in the Helderberg Mountains of eastern New York

and to which group the name Upper Helderberg was given by the geologists of that state. Of this group the Caudagalli grit, Schoharie grit, and Onondaga limestone give out before reaching Michigan, while the Corniferous is the sole representative here. This was so named from the beds and nodules of hornstone which seem quite characteristic of it (cornu, a horn; fero, I bear), both in New York and Michigan. Newberry and the Canadian geologists generally have used the term Corniferous in referring to the limeA. Winchell and Orton have preferred Upper Helderberg, although the former in 1886,* includes the four New York members under the general term Corniferous Group, following Dana.†

Rominger in his report of 1876 uses Helderberg alone to include this Dundee and the underlying so called Monroe beds, but recognizes an upper and a lower division. By early geologists the Hamilton, Corniferous and Niagara limestone in the states to the south and west, were known collectively as the "Cliff limestone." In his state report for 1893, Hall proposes "Onondaga" for the two beds originally designated Onondaga and Corniferous, the hornstone being found distributed throughout the series. In view of this use of terms to

*Geological Studies, p. 390.

+Two papers by N. H. Winchell before the American Association for the advancement of Science refer to the correlation of these limestones and may be summarized here. In 1873 (p. 100) a paper on the Devonian limestone in Ohio gives a section of five members, the bottom one, the Sylvania sandstone (?) being considered equivalent to the Oriskany. The two upper members are bluish and the author contrary to Newberry, would place them with the Hamilton, although they are colored Corniferous on the Ohio County maps. The third member is a light saccharoidal crinoidal limestone (our Dundee limestone?), and the fourth a vesicular or compact magnesian limestone (Monroe beds above the Sylvania?) often popularly mistaken for sandstone. In 1875 (part II p. 57) "On the Parallelism of Devonian Outcrops in Michigan and Ohio," he returns to the discussion of the border line between Hamilton and Corniferous, and shows how A. Winchell on paleontological grounds referred most of these Devonian limestones to the Hamilton, reducing the Corniferous to insignificant dimensions, while Newberry called them all Corniferous, and Worthen called the blue argillaceous limestones Hamilton (our Traverse), and the lower light colored assigned to the Corniferous. According to the author we have the following section from above: Blue limestone.

1.

2.

3.

Crystalline crinoidal limestone.

Arenaceous limestone.

The Water-lime of Ohio, beneath, has three different lithological aspects, to wit: thin bedded, fine grained drab, with distorted wavy bedding: harsh heavy bedded magnesian with wavy bituminous or carbonaceous films; in patches brecciated, this structure obliterating the true bedding and hardening the whole mass. Thirteenth annual report of the State Geologist, Vol. I, 1894, 207.

designate the same bed of limestone, it seems wise to retain, in a report of this character, the local name given by the present survey.* § 18. General data.

An inspection of the geological map of the county (Plate I), shows the Dundee beds striking northeast and southwest, forming a belt, varying in breadth from four to five miles? This enters, from Lenawee County, the northwestern part of Summerfield and the southwestern corner of Dundee townships, grazes Raisinville and forms the southeastern half of London and the northwestern half of Exeter townships, passing into Wayne County. Although conformable with the lower Traverse beds the general dip to the northwest is believed to be less than that given for the upper Traverse and lower St. Clair beds. It is probably from 20 to 25 feet to the mile upon an average, although locally it may be much more or much less. Mr. T. J. Brandt, foreman of the Christiancy quarry, on the Macon, for a number of years, estimates the dip in the 40 rods across as three feet, or twenty-four feet to the mile, and to be in the direction of W. N. W. In the Pulver quarry at Dundee it is much greater, being four and one-half feet in 200, or about 119 feet to the mile, and evidently local. The line of junction of the Dundee with the Monroe is believed to cut through Petersburg and very near Raisinville postoffice. At the latter place, however, the rock lies too deep to be reached by the river and there are no exposures in the bed for some distance upon either side, the river being through this region deep and sluggish. The highest surface elevation of the rock is at the county line, west of Petersburg, where it is 650 feet above tide level.

A rearrangement of the New York series has been recently proposed by Clarke and Schuchert in Science, December 15, 1899. (See also Amer. Geol. February, 1900.), The following portion includes the rocks described in this report: System. Stage.

Group.

[Chautauquan. {Chemung beds.

Michigan equivalent.

Neodevonic.

Devonic..

Mesodevonic.