TRILOBITES of Black Cat Mountain George P. Hansen
Geologic Age

Most of the rocks around Black Cat Mountain are from the lower-most Devonian period. This period occurred in the middle of the Paleozoic era, which can be visualized in the chart found at the website: Warning, this is a large file, so if your connection is slow you might want to go get something to drink while waiting for it to come up.

The Devonian time scale was recently re-calibrated from thirteen different exposures around the world that allowed dating from uranium decay sequences.  Based on these measurements, Bernard Kauffman reported the time scale below in terms of various conodont zones.  The rocks of Black Cat Mountain are characterized by the presence of Icriodus woschmidti postwoschmidti, which is the lowest conodont zone of the period.  I redrew Kauffman's chart, and expanded the view of the Lochkovian conodont zones, so they would be more visible here.  From this, you should be able to see that Black Cat Mountain represents rocks that are lowest Devonian in age, almost 418 million years old.
  This makes it the Lochkovian stage of the lower Devonian.

If the reader ventures onto the Related Websites page of this site, they will find other ages listed for the lower boundary of the Devonian, ranging from 410 to 416 million years.  This is because Kauffman's work is still very new, is still being reviewed and yet to be generally accepted among geologists.  For an interesting contrary perspective to some of Kauffman's approach, see Valenzuela—Ríos, J. I., and S. García López (1998), "Using conodonts to correlate abiotic events: An example from the Lochkovian (Early Devonian) of NE Spain," Proceedings of the Sixth European Conodont Symposium (ECOS VI) Oviedo, Spain, H. Szaniawski, ed., Palaeontologia Polonica 58: 191—199.

Huntoniatonia lingulifer
. This is the same specimen shown in Figure 20 of Chapter 5.  (Photograph by G.P. Hansen)