The Stafford Limestone and Levanna Shale are Middle Devonian age stratigraphic layers found in the western and central New York State area, including near Blossom, NY, as members of the Hamilton Group.

These units represent a sequence of rock layers in the following ascending order (from oldest/bottom to youngest/top):

1. Stafford Limestone Member (or Mottville Member in Central NY)

   • Position: Lies at the base of the Skaneateles Formation (which is part of the Hamilton Group). It typically overlies the dark shales of the Marcellus Formation (specifically the Oatka Creek Member).

   • Lithology: A relatively thin, compact limestone that is often gray but weathers to a chocolate-brown color. It can be somewhat shaly in places or highly calcareous and massive in others.

   • Significance: Marks a brief period of tectonic quiescence and relatively clear water deposition, representing the first major invasion of the Hamilton Group's typical fauna from the west.

2. Levanna Shale Member

   • Position: Overlies the Stafford Limestone Member.

   • Lithology: Primarily a dark gray or black shale that is characterized by a fauna of "Marcellus facies" (meaning a typical fauna found in Marcellus-type black shales). It is part of the Skaneateles Formation.

   • Thickness and Facies: There is a notable increase in the black shale facies to the west (towards Lake Erie). The Levanna Shale is essentially the undifferentiated "Marcellus or Leiorhynchus facies" of the Skaneateles Formation where its internal subdivisions (like the Mottville/Stafford and Centerfield members) cannot be readily distinguished.

General Stratigraphic Context

In Western New York, the Stafford Limestone and Levanna Shale fit into the Middle Devonian stratigraphy as follows (in ascending order):

Geologic Unit (Age: Middle Devonian)

Main Description

Ludlowville Formation (Base marked by Centerfield Member - often a limestone)

Overlies the Skaneateles Formation.

Skaneateles Formation

Predominantly shale unit.

Levanna Shale Member

Dark gray to black shale (Upper part of Skaneateles).

Stafford Limestone Member

Thin, gray/brown limestone (Basal part of Skaneateles).

Marcellus Formation (Oatka Creek Member)

Dark, fissile, organic-rich black shales.

Onondaga Limestone

Widespread limestone (Underlies the Hamilton Group).

Export to Sheets

The recognition of the Stafford Limestone is critical in Western New York as it is one of the thin limestone members that help reliably differentiate the major shale units of the Hamilton Group, marking the base of the Skaneateles Formation and separating it from the older Marcellus Formation.

https://research.ebsco.com/c/ix3dnl/viewer/pdf/prz6giqtij 

From Bob: "So for Blossom,  referencing the pic, top layer is onondaga LS for the man made wall (upper right). Below that is the Centerfield. That would be at least the 3 layers seen in the pic. Possible it may also include the slope layer that touches the creek bed. That would then be the Levanna shale."