| Figure 1. Carbonate concretion. Pen and ink
illustration of a large, "remarkably symmetrical" concretion within Middle
Mississippian "Rock Island Sandstone" strata in Muscatine County,
Iowa (from Whitney, J.D. 1858. County Geology [Continued]. in
Hall, James and J.D. Whitney Report on the Geological Survey of the State of Iowa:
embracing the results of investigations made during portions of the years 1855, 56 &
57 [vol. I, part I:Geology]) |
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| Figure 2. Carbonate
concretions. Imatra stones from Pleistocene lake deposits in Connecticut.
(from Dietrich, R.V. and Skinner, B.J. 1979. "Rocks and Rock Minerals," New
York:Wiley; photo by B.J. Skinner) |
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| Figure 3. Carbonate concretion. One of the
"Moeraki boulders," large septaria that have been weathered out of the Paleocene
Dannebirke Formation, along the Pacific coast south of Hampden and north of Moeraki Point,
South Island, New Zealand. (photo by R.V. Dietrich) |
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| Figure 4. Carbonate
concretions. "Garden of concretions" in the Lower-Middle Devonian Millboro
Formation, East Radford, Virginia. (photo by T.M. Gathright, II) |
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| Figure 5. Carbonate concretion.
Fossil-bearing (Annularia stellata) concretion from Pennsylvanian strata of the famous
Mazon Creek Area, Illinois. (sketch from Keys to Identify Pennsylvanian Fossil Plants of
the Mazon Creek Area. 1990, Downers Grove (Illinois): ESCONI, sketch by Don Auler) |
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| Figure 6. Carbonate concretion.
One of several concretions in a siltstone/shale sequence in the Middle Pennsylvanian
Pottsville Formation along West Virginia Turnpike. (photo by T.M. Gathright, II) |
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