Lab
The Local Stratigraphy lab is an investigation of the Middle Devonian age Onondaga Limestone, a geological formation exposed in an east-west band across western New York. In this lab, we visit four sites north of Geneva. We trace the formation from its bottom to its top, examining the rocks at each stop.
Stop 1
Stop 1. Base of Onondaga Limestone.
Stop 1. Shaly layers at base of exposure.
Stop 1. Chert nodules interbedded with limestone. Camera case for scale.
Stop 1. Rock sample reacting to hydrochloric acid. Camera case for scale.
Stop 2
Stop 2. Limestone exposure near Flint Creek.
Stop 2. Limestone beds.
Stop 2. Interbedded chert nodules and limestone. Note how cherty layers alternate with limestone layers. Camera case for scale.
Stop 2. Rock sample reacting to hydrochloric acid.
Stop 2. This picture shows how the lime mud was deformed by the weight of overlying sediment. This kind of phenomenon is called, not surprisingly, "soft sediment deformation". Camera case for scale.
Stop 3
Stop 3. 15 meter black shale outcrop across Flint Creek.
Stop 3. More outcrop.
Stop 3. Shale pebbles at creek edge.
Stop 3. Shale samples in lab.
Stop 4
Stop 4. Limestone block with shale and burrows.
Stop 4. Limestone block with burrows.
Stop 4. Limestone block with burrows.
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Definitions
- Middle Devonian: The geological time scale is divided into periods based on unique events in the earth's history. The Devonian is one of these periods. The Middle Devonian lasted roughly from 387 million years ago to 370 million years ago.
- Formation: The basic unit for the naming of rocks in stratigraphy: a set of rocks that are or once were horizontally continuous, that share some distinctive feature of lithology, and are large enough to be mapped. This body usually represents an ancient environment or a suite of related environments. For example, a formation might represent an ancient lake, including shore, shallow and deep environments.