Montmorillonite A Factor in the Breakdown of Concrete Aggregate

This investigation (Dorheim, 1950) was made m an effort to identify mineralogical or textural characteristics of limestones that might affect the durability of concrete. The Iowa State Highway Commission has found that when certain limestones were used as coarse aggregate in concrete, that concrete gave excellent service in paving. Other limestones that responded to standard testing procedures in a similar manner, gave very poor results when used in concrete paving

Devonian Outlier in Jackson County, Iowa

Recent grading of a road in Jackson county, Iowa, led to the uncovering and subsequent discovery of an outlier of Devonian limestone. This outlier was first noted while the author was searching for a suitable quarry site in Jackson County, southeast of Maquoketa. The area is located south of center section 33 Maquoketa Township, just about one-fourth mile north of the Clinton-Jackson county line. With the exception of an area along the Mississippi River and a smaller area around the town of Preston, where Ordovician rocks are exposed, Jackson County is underlain by Silurian dolomites of the Niagara Series. Other than the Devonian outlier found by Norton near Canton, the nearest known Devonian is approximately thirty-five to forty miles south and south-west

Stratigraphic Leak at Springville Quarry

Lime Creek Shale, containing an Upper Devonian conodont fauna, is exposed below Middle Devonian rocks at a quarry near Springville, Iowa. The occurrence is interpreted as a stratigraphic leak and is cited as further evidence of this condition occurring in a karst Devonian terrain

The Economic Geology of The Iowa Devonian

The Devonian System, in Iowa, is exposed in a belt about 50 miles wide extending along a line from Mason City to Muscatine. With the exception of the Shell Rock Formation the Upper Devonian is essentially elastic, dominantly shale. The Middle Devonian is dominantly carbonate, and the lower Devonian, known only from subsurface, appears to be dominantly chert with minor amounts of carbonate (Parker, 1967)

Unusual Exposure of Silurian-Devonian Unconformity in Loomis Quarry Near Denver, lowa

In the Loomis quarry, located in the NW1/4 sec. 29 T. 91N., R. 13W., Bremer County, Iowa, there is an unusual exposure of an unconformity between the Silurian and the Devonian sediments. Several Niagaran hummocks rise approximately 30 feet above the general Silurian level with Devonian sediments (Cedar Valley and Wapsipinicon) deposited against the Hanks of the Niagaran remnants. A basal Wapsipinicon breccia is exposed in this section. Chert from the Silurian forms an important part of the breccia

Recent Gypsum Exploration in Iowa

Until recently all interest in gypsum in Iowa, with the exception of brief activity at Centerville, was centered around the shallow deposits in the Fort Dodge area. During the past five years, however, interest in deeper gypsum has developed in the southern part of the State and both industry and civic groups have participated in exploratory drilling programs. With the exception of the Centerville area, this interest started with information obtained from the files of the Iowa Geological Survey

Resolving Discrepancies Between Surface and Subsurface Studies of the Maquoketa Formation of Northeast Iowa

The Maquoketa formation in the outcrop area has been assigned a maximum thickness of 257 feet by earlier surface workers. Recent subsurface study in the same area reveals a thickness of 300-320 feet of Maquoketa sediments. Until now the correlation of subsurface units to recognized surface members has been hampered by this discrepancy. The recognition and identification of a new unit in the Elgin member of the Maquoketa formation, and a greater measured thickness of the Isotelus zone has resolved this difference