UGA Stratigraphy Lab

 

Mineralization

Shown below is a iron mineralization developed along foresets and set boundaries of cross-stratified echinodermal grainstone. This mineralization is developed over a one-meter thick interval at a major flooding surface that separates underlying shallow subtidal carbonates from overlying graptolitic black shales. This photograph was taken in the Middle Ordovician Fetzer Limestone at the Dandridge City Park in eastern Tennessee.

Shown below is pyritization along a hardground developed on a combined sequence boundary and transgressive surface. This hardground and possible karstic surface, with up to 10 cm of relief locally, is locally encrusted with pyrite that weathers to a rusty color. This particular horizon can be traced for tens of miles and is so distinctive that it can be identified from the highway. This photograph was taken in the Upper Ordovician Leipers Limestone near Goodlettsville, Tennessee.

This next photograph shows a more pervasively developed pyritization along another combined sequence boundary and transgressive surface. This interval also contains phosphate coated pebbles. This photograph was taken at the contact between the Upper Ordovician Leipers Limestone and Arnheim Formation near Hendersonville, Tennessee.

Shown below is an example of pervasive phosphatization along a combined sequence boundary and transgressive surface. This surface, blackened from the phosphatization, shows evidence of several episodes of phosphatization, boring, and erosion. This photograph was taken in the Upper Ordovician Arnheim Limestone near Hendersonville, Tennessee.

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