Iowa Geological Survey Volume 12 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1902 Excerpt: ...surface of this member is here exposed over an area of several square rods. It presents numerous rounded elevations two to four feet in height and ten to twenty feet in diameter. These elevations appear as if some force from below had pushed the strata vertically upward at those points. Many of the layers, both of numbers.1 and 2, show beautiful ripple marks which are exposed over an area several square feet in extent. This ripple marked sandstone as well as the bands of oolite which appear in the first member plainly tell us that this was the site of an ancient beach at the time these rock materials were laid down. Number 3 is a layer of almost pure flint. A few rods west of this place, across the railroad track, there is exposed in corresponding beds a second band of chert, two feet in thickness, about four feet above the first. It is not surprising that the fossil Lithostrotion canadense always occurs in a silicified condition when the rocks of this horizon contained silica in such quantities as to make possible the deposit of these bands so closely overlying the beds in which that coral is found. The heavy layers of numbers 1 and 2 in the above section, composed of magnesian and arenaceo-magnesian limestone, and containing the fossil Lithostrotion as here found, represent the Fig. 48. Exposure of limestone in Parkins' quarry, showing the oven layers of the Pella Hub-stage. Springvale beds. The broken and irregular layers of sandstones and shales together with the brecciated or oolitic beds of limestone, embracing numbers 3 to 7 inclusive, belong to the Verdi phase; while numbers 8, 9, 10 and 11, consisting of hard, finegrained, evenly bedded limestone and containing numerous fos sils, as given above, constitute the Pella beds as they are developed withi...