KARST OF THE EASTERN UPPER PENINSULA, MICHIGAN

Michigan’s Eastern Upper Peninsula (EUP) is extensively underlain by Paleozoic dolostones which host a variety of karstic and pseudo-karstic features. The Niagara Escarpment is a prominent feature of the area and is formed by the mid-Silurian Manistique Group and Engadine Group dolostones. The entire EUP was extensively glaciated during the Pleistocene glaciations and was inundated by Glacial Lakes Algonquin and Nipissing during the final glacial retreat. The karst features of the EUP are currently understood to be post-glacial in origin given their shallow depth; in fact, most of the features in the EUP are surficial with relatively little cave development. Most karst features occur in conjunction with paleo-lake levels, as these areas have thinner soil and till blankets.

The EUP is host to sinkholes, sinking streams, and swallets. These features drain a mix of deranged drainage areas along with swallowing entire creeks. Several springs have been documented in the area as well; however, dye-tracing efforts have not been conducted to demonstrate flow paths. Preliminary discharge calculations suggest some possible connections; however, qualitative and quantitative dye-tracing remains a goal for future work. Many of these recharge features are also found in conjunction with grikes fields.

Grike fields, alvar, and limestone pavements are also commonly found throughout the EUP. Grike fields range in size from 10’s m² up to about 1 km². Grikes broadly follow the regional joint sets, though there are slight orientation differences among grikes in different formations. Small alvar and limestone pavements can also be found in the EUP, often in conjunction with grike fields. Alvar on Drummond Island, off the eastern end of the EUP is extensive and developed in mid-Ordovician carbonates.

Finally, caves are also found in the EUP. Only one significant epigene cave is known in the area – the Hendrie River Water Cave in the Fiborn Preserve. Additionally, there are a number of littoral caves and talus within and along the Niagara Escarpment that formed along former Lake Algonquin. Many of the grikes in the area appear to be connected and have fluid flow along them; with further exploration or more time to enlarge, there will undoubtedly be additional cave discoveries in the area adding to the already rich near-surface karst of the area.