Outstanding Natural Sites

in the Champlain Valley, NY

    The Clinton County "Flat Rocks" comprise a discontinuous belt of exposed sandstone pavement that extend approximately 30 km southeastward into the Champlain Valley from Covey Hill, P.Q.   They were created more than 12,000 years ago by the drainage of proglacial lake Iroquois and younger post-Iroquois proglacial lakes from the St. Lawrence Lowland to the Champlain Valley.  These catastrophic floods stripped large areas of their surficial cover and cut deep channels and plunge pools into the Potsdam Sandstone.  

     The falling levels of proglacial lakes in the St. Lawrence Lowland temporarily stabilized at the Covey Hill threshold creating glacial lake Frontenac.  Outflow from Lake Frontenac carved the deep chasm at The Gulf, which is presently occupied by a minor tributary of the English River.

map by D..A. Franzi, c.1999

   The walls of the chasm provide a microhabitat for an unusual moss and liverwort community.

photograph by J.C. Dawson, c.1999

Close-up of liverworts.

photograph by J.C. Dawson, c.1999

References:

Coles, J.J., 1990, By fire and by ice: The evolution of an unusual landscape: unpublished M.S. thesis, Department of Botany, University of Vermont, 49p.

Denny, C.S., 1974, Pleistocene geology of the northeastern Adirondack region, New York:  U.S. Geological Survey Professional Paper 786, 49p.

Franzi, D.A. and Adams, K.B., 1993, The Altona Flat Rock jack pine barrens; A legacy of fire and ice:  Vermont Geology, V.7, p.43-61.

Franzi, D.A. and Adams, K.B., 1999, The origin and fate of the sandstone pavement pine barrens in northeastern New York: Guidebook to Field Trips in Vermont and Adjacents Regions of New Hampshire and New York, New England Intercollegiate Geological Conference, 91st Annual Meeting, p.201-212.