862 THE JOURNAL OF GEOLOGY. 



Ueber Geroll- Thonschiefer glacialen Ursprungs in Kulm des Franken- 

 waldes. By Ernst Kalkowsky in Jena (Zeitschrift der Deut- 

 schen geologischen Gessellschaft. XLV. Band. i. Heft. Jan- 

 uar, Febuar und Marz, 1893, pp. 69-86.) 



In the midst of the shales and greywackes of the Upper Kulm of Frank- 

 enwald, there is a peculiar sort of conglomerate (geroll-thonschiefer). This 

 conglomerate is exposed at but few points. It is not certain that all the 

 exposures belong to one horizon, though nothing is known which forbids this 

 conclusion. The demarkation of the conglomerate from the underlying and 

 overlying beds is sometimes, but not always, distinct. The conglomerate has 

 a known thickness at one point of at least 18 m. It is wholly unstratified, and 

 is made up of something like equal parts of clayey matter, and well-rounded 

 stones (gerolleii). The sand grains are conspicuously angular, while the larger 

 stones are as distinctly well-rounded. In no case do the sandy or stony mate- 

 rials show any traces of arrangement suggestive of stratification. The 

 stony material varies in size from pebbles to small boulders, the largest being 

 22 X 29 X 12 c. m. In connection with these limitations in size it must be 

 remembered that the exposures are very limited. While it is difficult to 

 determine the origin of the stony material in all cases, it does not seem 

 necessary to suppose that it is of very distant origin. The author considers 

 the various possibilities concerning the origin of this conglomerate, and con- 

 cludes that it is the work of rivers which were affected by floating ice. The 

 conglomerate is therefore an indication of cold climate in the adjacent 

 regions at the time of its formation. The author thinks that the Carbon- 

 iferous ice period, belief in which seems not to be without foundation, may be 

 brought into connection with the cold climate indicated by this conglomerate 

 bed in the upper Kulm. He further thinks that the cold climate of the Kulm 

 may have made itself felt over wide areas, since more or less extensive con- 

 glomerate beds of this age occur in widely separated parts of the German 

 Empire. R. D. S. 



