In a general way the lithological characters of the Burlington limestones, including both the lower and upper divisions, are the same. It is true that some layers are more compact than others, some more massive and a few are even crystalline enough in texture to imperfectly resemble marble, yet they all owe their origin to the same source. The material comprising them is almost wholly crinoidal. To such an extent is this true, that, with the exception of a very few layers, it is scarcely possible to find a cubic inch of rock that does not show its crinoidal origin. There are a few layers of shales, clays, etc., but for the most part they are quite thin and form but a very small part of the whole. However, they are deserving of some attention and I shall take occasion to refer to at least one or two of them specifically.
Proceedings of the Iowa Academy of Sciences
©1893 Iowa Academy of Science, Inc.
Fultz, F. M.
"Evidences of Disturbance During the Deposition of the Burlington Limestones,"
Proceedings of the Iowa Academy of Science, 1(Pt. 4), 56-58.
Available at: https://scholarworks.uni.edu/pias/vol1/iss4/21