April, 1920] Marl Deposits in Ohio 111 



CASTALTA MARL. 



In Erie County, west of Castalia and east of Sandusky- 

 Bay, is a mari deposit extending over several miles, with the 

 surface about thirty feet above the level of Lake Erie, about 

 ten feet deep where opened, and underlaid with clay. The 

 marl has been used, for many years, for manufacturing Portland 

 cement, and anal3^ses have shown it to be over ninety-nine per 

 cent carbonate of lime. Most of it is soft, but at places with 

 hard concretions, and here and there are blocks and even rock- 

 like masses of travertine, at least partly formed among reeds 

 and rushes, and mosses, mostly Hypnacece so far as seen. The 

 surface of most of the area is nearly level, and dry, covered with 

 grass and weeds and locally with shrubbery. Some parts are 

 still marshy with a luxuriant marsh vegetation, and in places 

 even covered with open water. 



The marl is rich in shells, from bottom to top, and evidently 

 the mollusks had once inhabited the region. At some places 

 they were found in extraordinary numbers; for example, in a 

 perpendicular, artificial bluff at the end of a digging, about 

 four feet from the surface, there was a layer about three inches 

 thick, which was chiefly composed of small and minute shells. 

 The marl of this layer was quite soft, loose and of finer grain than 

 above and below, and through atmospheric influences had dis- 

 integrated to fine sand and dust. The dust and clean shells had 

 accumulated on a narrow ledge at the foot of the bluff. Some- 

 what less than a quart of it was scooped up and taken along, and 

 at a conservative estimate there were over a hundred thousand 

 shells in it, representing more than fifty species, for the most 

 part land snails. Most common was Carychium, probably more 

 numerous than all others combined, then: PupillidcB, small 

 ZonitidcE, Ilelicodiscus, Strobilops, also Segmentina, etc. The 

 largest were Polygyra nionodon and hirsiita. Evidently these 

 snails were washed together and deposited as drift by the outer 

 edge of an exceptionally high and widespread flood. The out- 

 cropping layer could be followed on a stretch of more than forty 

 feet, though not everywhere with the same wealth of shells. 



Most of the larger shells were picked up at various places 

 where a steam shovel had been working but many were taken 

 in situ. Sif tings for the smaller ones were gathered here and 

 there, especially where they had been washed together by 



