Photos from Historical Geology Field Trip #

Photos from Historical Geology Field Trip #3

Stop 1: Fossil saplings leaning and bent to the right, preserved in sandstone interpreted to have been deposited by a crevasse splay event.

Stop 5--Left: The Stanley Fm crops out in the upper right area; it is characterized by beds dipping gently to the right. To the left, about 3/4 of the highwall is occupied by the Hatton Tuff. It is strongly jointed with joints dipping steeply to the left. The joints give the impression of a cross-cutting structure, but the actual contact follows Stanley bedding. Right: Photomicrograph of a thin section from the rock on the left side of the other photo. Beautiful bubble-wall shards prove this is a tuff.

Stop 5: Beautiful Bouma sequence in Stanley Fm rocks. This was exposed in the sequence of rocks seen in the upper right of the left-hand photo above. This demonstrates the deep-water nature of the basin into which the Hatton Tuff was deposited.

Stop 5: Awesome chevron folds in Arkansas Novaculite in the Hatton Quarry--testamony to the tectonic stresses involved in the Ouachita orogeny.

Stop 6: Slate quarry at Slatington (Missouri Mtn Shale).

Stop 8: Bedded gypsum and other sediments at the Highland Gypsum mine. Note: not far beneath here, well drillers hit hard folded Paleozoic rocks such as seen above. We are just a little above the regional angular unconformity.

Geologic map of the world famous Magnet Cove intrusive complex. (Map compliments of the Arkansas Geological Commission).

Stop 10: Xenoliths in nepheline syenite of Diamond Joe quarry.

Stop 11: Anticline and syncline in hornfelsed Stanley Fm.

Stop 11: Lamprophyre dike (Tim Wilson is sampling it) cuts through the core of an anticline in the hornfelsed Stanley Fm. The cross-cutting relations here and the hornfelsed nature of the Stanley provide physical evidence that the Magnet Cove magmatism post-dated the Ouachita orogeny.

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