TiogaB-Stafford

Devonian Geology

Roughly forty percent of New York State is underlain by Devonian rocks. Project research ranges across a broad spectrum of geologic problems including sequence stratigraphy, tectonics, and sedimentation, sedimentary basins, high-resolution event and cyclic stratigraphy, and both marine and terrestrial systems. A chief research interest is K-bentonites (ancient volcanic ash layers), and the full range of processes involved in their sedimentology and stratinomic (preservational) history.

Volcanic Ash Layers in Sedimentary Rocks

Volcanic ash layers in sedimentary rocks, though rare to uncommon, are key sources of a variety of geological information. NYSGS research on ancient (Devonian-age) volcanic ash layers in New York includes their discovery and documentation, their use for correlating rocks across broad regions of eastern North America, and radiometric age
dates. They also provide information about explosive volcanic eruptions in the region during the Devonian.

More in-depth research of ash layers examines their sedimentation history. Following an explosive volcanic eruption, ash settles onto the floor an ocean or lake. Study of Devonian ash layers in New York indicate that many ash layers have a complex history of deposition – that a single layer does not always represent a single volcanic eruption. It also raises questions about how often an ash layer deposited on a shallow sea or lake floor becomes preserved in the rocks. A broad range of physical, biological, and chemical processes (e.g., waves, currents, storms, sedimentation, burrowing, the availability of oxygen) may lead to the preservation, modification, or destruction of an ash layer. Current studies examine ash bed preservation in ancient rocks from shallow seas (Devonian Appalachian Basin, NY and region) and small and large lake deposits (Eocene
Florissant and Green River formations, CO and WY).

 


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