A large majority of the aggregate products The Kraemer Company Manufactures would be referred to as Limestone. This simple term does not do justice to the complex and scientific approach to producing aggregates today. The crushed limestone that we produce actually comes from a fairly select geological formation, the infographic to the right “Bedrock stratigraphic units in Wisconsin” comes from the Wisconsin Department of Transportation – Geotechnical Manual. The Prairie du Chien group in that graph is where the majority of the our products originate. In the regions where we produce quartzite products these actually come from a group below what is represented on the chart.
Here is what the Geotechnical Mannual has to say about the history of Wisconsin’s rock:
2-2.2.2 Bedrock Distribution and Age
The general distribution of the various rock types across the state can be seen by referring to Figure 2, entitled
“Bedrock Geology of Wisconsin”, prepared by the Wisconsin Geological and Natural History Survey (WGNHS).
The igneous and metamorphic rocks are the oldest in the state and fall into the Precambrian time period. The
rocks range in age from approximately 1 billion years to about 2.8 billion years, and form the bedrock surface
under most of the northern portion of the state. The great age of these rocks along with the effects of multiple
stages of volcanism, erosion, deposition, and metamorphism make the interaction of these rocks very complex.
They are considered to be part of the Canadian Shield, a large area of ancient rock units forming the core of the
North American continent. The igneous and metamorphic rocks extend under southern Wisconsin but for the
most part are covered by the younger sedimentary rocks. However, some exposures of Precambrian rocks do
occur, most notably quartzite that forms the Baraboo bluffs in Sauk and Columbia Counties. Associated with the
igneous and metamorphic Precambrian era is an area of sedimentary rocks extending out from the south shore
of Lake Superior. These Lake Superior sandstones, shales, and conglomerates are thought to be of
Precambrian age but somewhat younger than the other igneous and metamorphic rocks in this area. All of
these sandstone, shale, and conglomerate deposits display a distinct reddish brown color.
The sedimentary rocks of southern Wisconsin form distinct layers covering the igneous and metamorphic
basement rocks. They form a distinct pattern with the oldest rocks exposed to the north overlain by
progressively younger rocks to the south and east. The oldest of the sedimentary rocks is a series of
sandstones of Cambrian age. These are overlain by two distinct limestone sequences separated by a layer of
sandstone followed by a layer of shale, all of Ordovician age. These sequences are overlain by Silurian age
limestone extending across eastern Wisconsin. The uppermost rock unit is a small area of Devonian age shale
and limestone located along the Lake Michigan shoreline in Milwaukee and Ozaukee counties. There are no
rocks younger than Devonian age in Wisconsin even though these are present in adjoining states. While it is
possible that some of the younger sedimentary rocks may have been deposited in Wisconsin, they have been
removed by weathering and erosion.
Curious to learn more about Wisconsin geology or about what goes into manufacturing the goods used in the roads and bridges you drive on? Check out the DOT Geotechnical Manual page:http://wisconsindot.gov/Pages/doing-bus/eng-consultants/cnslt-rsrces/geotechmanual/default.aspx
