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Roadcut Section F

Roadcut Section F:

The siliciclastic mudstone with dispersed crinoid grains at the base of Section F comprises channel-fill A that has a minimum, inclined thickness (perpendicular to internal stratification and to the lateral extension of the basal erosion surface) of 12-meters, making this channel one of the largest exposed in the TN52 roadcuts.  The basal erosion surface can be seen on the far western part of the roadcut and is defined by the abrupt transition from planar, horizontal bedding to uniformly inclined, planar bedding.  This is one of the few examples in the TN52 roadcuts where mudstone channel-fill cut into mudstone substrate can be clearly identified.

The dark gray, fossiliferous shale of unit B only occurs in Sections E and F.  Large (2-4 cm) Spirifer sp. brachiopod shells, solitary corals, and crinoid columnals are common.  The basal contact is a scour surface that truncates the underlying siliciclastic mudstone of channel-fill A.  The upper contact with the overlying crinoid grainstone of unit C is sharp and abrupt.      

The crinoid grainstone of unit C has planar, horizontal bedding.  This crinoid grainstone most likely correlates with the unit C crinoid grainstone of Section E and the upper crinoid grainstone (unit 1) of channel-fill A in Section B.