Features of interest
Vertical section of 30+ ft . Massive tripolite chert replacement of limestone with frequent residual limestone remaining. Original limestone bedding disrupted throughout replacement areas. Dense gray limestone at top of outcrop (4 ft). Dark gray concoidal fracture chert at base of outcrop with well-developed stylolites (implying ? depth of burial greater than 3000 ft )
Lithology present
Support material available
Vertical section of 30+ ft . Massive tripolite chert replacement of limestone with frequent residual limestone remaining. Original limestone bedding disrupted throughout replacement areas. Dense gray limestone at top of outcrop (4 ft). Dark gray concoidal fracture chert at base of outcrop with well-developed stylolites (implying ? depth of burial greater than 3000 ft )
Lithology present
Limestone, tripolite chert, black chert
State/County
State/County
MO / McDonald County
Access
On US71
Photos (20 iPhone)
Site visit history
C. Liner 11/14/2012 |
| Figure 1. General view of outcrop. |
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| Figure 2. Limestone capping thick zone of mixed limestone and tripolite. |
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| Figure 3. A theory of how tripolitic chert is formed. (a,b) Deposition and compaction of original calcite mineral grains. (c) Formation of secondary calcite cement, likely from near-surface high-carbonate groundwater activity along bedding planes. (d) Low-carbonate groundwater leaching of calcite cement, increasing porosity above 30%. (e) Infiltration of silica-rich fluids causing grain replacement of calcite by microcrystalline silica. The source of silica-rich waters required to make this replacement are of uncertain origin. |
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| Figure 4. Well-developed stylolites at contact between dark chert (above) and limestone (below). |
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