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Farther offshore away from the beach, finer grained sediment accumulated
and chemical sediment precipitated to form limestone and a closely related
rock called dolostone. In this environment, marine life was abundant.
Shells and skeletons of various clams, snails, corals, etc., are preserved
in the limestone of southern Minnesota. Limestone is typically tan to
gray. It may be massive or bedded in layers with sandstone and shale.
In places fossils may readily be found (see Minnesota at a Glance: Fossil
collecting in the Twin Cities area). Many quarries in southern Minnesota mine and crush limestone for aggregate. Coarsely crushed limestone and dolostone are used for road ballast and making concrete; finer grained aggregate can be used for landscaping; powdered limestone is used on farm fields. |
