Features of interest
Vertical section of 20+ ft . General lithology limestone and white to red-stained chert. Lateral gradation from massive chert-free limestone to rippled, flow-laminated crinoidal grainstone and irregular (lenticular?) replacement chert bodies with abundant fossil casts. Complex relationships between grainstone and chert bodies, perhaps due to irregular limestone to chert replacement process. Local angular unconformity. Carbonate bank outflow channel?
Lithology present
Support material available
Vertical section of 20+ ft . General lithology limestone and white to red-stained chert. Lateral gradation from massive chert-free limestone to rippled, flow-laminated crinoidal grainstone and irregular (lenticular?) replacement chert bodies with abundant fossil casts. Complex relationships between grainstone and chert bodies, perhaps due to irregular limestone to chert replacement process. Local angular unconformity. Carbonate bank outflow channel?
Lithology present
Limestone, white chert
State/County
State/County
AR / Madison County
Access
AR45 at intersection of Madison County 8382
Photos (22 iPhone)
Site visit history
C. Liner 2/14/2013, 5/24/2013 |
| Fig 1. General view of outcrop with local angular unconformity near base. |
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Fig 2. Note upper section lateral gradation right-to-left from massive limestone to thin-bedded, rippled limestone beds, possible indicating the edge of a carbonate bank flow channel.
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Fig 3. Flow laminated crinoidal grainstone beds interleaved with replacement chert bodies containing abundant fossil casts. The grainstone weathers more easily forming re-entrant zones between the hard, slowly weathering chert bodies.
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Fig 4. Detail of the complex relationship between crinoidal grainstone and adjacent chert bodies. Note abundant fossil casts in the chert.
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