THE KARST OF MACKINAC COUNTY, MICHIGAN: WHERE WE’VE BEEN AND WHERE WE’RE GOING

The karst of Mackinac County (Upper Peninsula), Michigan is poorly understood and an open field for research. Much of the area is contained within the eastern unit of the Hiawatha National Forest. The karst bearing rocks of Mackinac County are early Silurian dolostones, primarily within the Engadine Group. Common karst features include alvar, grikes (kluftkarren), solution pans, sinks, and springs. There are also a few caves in the area. Within these rocks there are also pseusdokarstic features – littoral caves that formed ~12,000 years ago within the Niagara Escarpment when much of the area was covered by Lake Algonquin. Also created during this period of higher lake level, and the lower Lake Nipissing are numerous boulder fields which have been mistaken for karst features.

Work began describing and mapping these features as part of the Niagara Environmental Impact Statement in the 2000’s. In these early phases of work features many karst features were delineated. It was discovered at this time as well that the karst features seemed to occur at the same elevations of prior lake levels in conjunction with other coastal features (e.g. littoral caves, strand plains, and boulder fields). Very little exposed karst exists outside of these prior lake levels. Subsequent efforts have focused on the description of individual karst feature types, primarily focused on grikes, sinks, and springs.

Looking to the future there is much work to be done looking at the karst of the area. Future analysis is focused on several main themes: 1) detailed sedimentologic and stratigraphic analysis to better understand the nature of the host rock; 2) dye tracing to determine groundwater flow paths; 3) detailed mapping of grikes to determine genesis; 4) geophysical analysis to map karst buried under soils; 5) development of a comprehensive model for karst development and distribution; 6) construction of geologic maps for the area using GIS and ground truthing; and 7) expand field work to investigate the Ordovician carbonates of eastern Mackinac County and Chippewa County to determine if there is any karst in those areas. There is much work to do yet to understand the karst of the Upper Peninsula Michigan.