470 



SCIENCE 



[N. S. Vol. XXXIX. No. 1004 



SPECIAL ABTICLES 



TILTED SHORELINES OF ANCIENT CRAIGTON LAKE, 

 OHIO ^ 



Description. — A lake bed mentioned by 

 Read,- by the present author^ and byDachnow- 

 ski* lies in a mature, branched, preglacial, 

 north and south, valley west of Wooster and 

 east of Ashland, Ohio. The lake which occu- 

 pied this bed shortly after the ice withdrew 

 is called Craigton Lake. It may be said to 

 center near Funk, Ashland county, and to 

 extend in three arms, southward seven miles, 

 northward about eleven miles and northwest- 

 ward twelve miles. The main north-south axis 

 is a little more than eighteen miles long. 



That such a lake^ really existed is abundantly 

 attested by beaches, cliffs, deltas, water-modi- 

 fied moraines and extensive flats of lake clays. 



A cursory examination of the features in 

 1912 suggested that the beaches were not now 

 horizontal and during the past summer careful 

 instrumental leveling starting from U. S. Geo- 

 logical Survey bench marks has been done at 

 several points along the lake plain. By this 

 means it was found that the beach lines are far 

 from horizontal. 



The delta surfaces at the northern end are 

 1,040 feet above sea level. Some little wave 

 work can be seen higher. Three miles and a 

 half southward the beaches are at about 1,020. 

 The altitude of 1,000-998 was found about a 

 mile north of Funk. At Craigton the beach is 

 973 feet high and at the southern end we found 

 it to be 960 feet with no wave work higher. 

 Allowing 5 feet for possible fans or outwash 

 deposits on the delta at the upper end, where 

 the proper level on which to read is extremely 

 difficult to determine, we still have 1,035 here 



1 Summary of a paper presented before the Ohio 

 Academy ef Science, at Oberlin, O., November 29, 

 1913, and published by permission of the state geol- 

 ogist. 



2M. C. Read, Geol. Surv. Ohio, 1878, Vol. III., 

 pp. 519-529. 



3 Geo. D. Hubbard, Am. Jour. Sci., 1908, Ser. 

 4, Vol. XXV., pp. 239^3. 



*A. Dachnowski, Geol. Surv. Ohio, 1912, Ser. 4, 

 Bull. 16, p. 134. 



s Full description of this evidence with maps and 

 section will appear in Amer. Jour. Sci. soon. 



and a difference of 75 feet in 18 miles, the 

 southern end being lower by this amount. 

 This means a tilting upward relatively at the 

 north with reference to the south end of about 

 4 feet in a mile. 



Interpretations and Correlations. — The post- 

 glacial tilting of the shorelines of the pre- 

 cursors of our Great Lakes has long been 

 recognized. Very little evidence has been 

 found of tilting south of the borders of our 

 present lakes. The long east-and-west aban- 

 doned beaches across Ohio show almost no tilt- 

 ing, but lines running more nearly north and 

 south are appreciably displaced. The evidence 

 presented above carries actual tilting 50 miles 

 south of the most southern part of Lake Erie, 

 itself the most southern lake. Furthermore 

 the rate of tilting is greater in this case than 

 that observed on many of the abandoned 

 beaches further north. 



Goldthwait^ who has worked extensively on 

 abandoned beaches to establish the amount and 

 kind of warping that may have taken place, 

 shows that the Algonquin beach is not tilted 

 south of a line through the middle of Lake 

 Michigan and Niagara Falls. In the same 

 paper he shows that the older Iroquois beaches 

 are tilted more than the Algonquin in the same 

 latitudes and that the tilting extends farther 

 southward for the Iroquois beach. He shows 

 that the tilting is greatest further north and 

 decreases southward, but he is unable to locate 

 any southern limit for the tilting. 



That the existence of Craigton Lake began 

 earlier than that of any of those preceding 

 even Lake Erie is easy to believe because of 

 its location with reference to the retreating 

 ice. Its site would be uncovered even before 

 that of Lake Maumee. That tilting in the 

 lake region began early is also shovsm by the 

 fact that Craigton Lake shorelines are tilted 

 more than such beaches as those of the Algon- 

 quin and Iroquois water planes. The warping 

 in Craigton Lake lines amounts to four feet 

 in a mile and is quite uniform for the 18 

 miles of length. It may be a little steeper in 

 the last two or three miles at the north end 



6 J. W. Goldthwait, G. S. A. Bull., Vol. 21 

 (1910), pp. 227-248. 



