ICE AGE Geology of Ice Age National Scientific Reserve of Wisconsin NPS Scientific Monograph No. 2

This book would not be complete without reference to a few other areas in Wisconsin that are worthy of being included in the Ice Age Reserve. Because of the limit on available funds particularly, but in part because of the bounds of practicality in administering and using some remote areas, not all desirable features are included in the nine areas previously discussed. Occasional reference to similar nearby features has been made in the text in connection with some of the recommended areas. These are not repeated here. Only brief mention of some of the other most important areas and the kinds of things they show or contain is given.

Without question by far the most important locality not now being included in the Reserve, as agreed upon, is the Natural Bridge and underlying Rock Shelter, Sk5, in Sauk County (Wittry 1959; Black 1959b; Parmalee 1959). I believe very strongly that this site should be in a scientific reserve now, and certainly should be in the proposed Ice Age Reserve. It is a unique locality that is in imminent danger of being irreparably damaged or destroyed. The bridge is part of a narrow spur of Upper Cambrian sandstone which rises 35 ft above a small picturesque glen. The opening under the arch is 15 ft high and is directly above the sandstone capping the shelter. Archeologic excavations and geologic study of the area establish man's presence at the close of the Valderan substage and suggest his presence during Twocreekan time. The rockshelter and bridge were carved by a combination of weathering and erosional processes shortly before occupancy by man. In the upper part of the deposits were hundreds of artifacts of chipped and ground chert, basalt, bone, teeth, and shell. Several hundred pounds of split deer bones and other faunal remains, hundreds of firebeds, and several artificial pits attest to man's presence. Three loess horizons and involutions are common to older strata in the shelter. Because we still lack a firm chronology to which to correlate the strata in the shelter and it by itself is not sufficient to establish a detailed chronology, half of the deposits in the shelter were left undisturbed. These are in constant danger of being destroyed. This would be tragic, for this is the oldest authenticated site for man in the Upper Mississippi Valley. Inclusion of this site in the Reserve would preserve it and provide a fitting location to bring man into the story of the Pleistocene. The bridge and surroundings are a beautiful natural attraction; the shelter and its story are a scientific must.

Nowhere in the nine recommended areas are there good examples of glacial striae on bedrock. Weathered striae are present on the higher bedrock ridges at the St. Croix Dalles. Some unweathered examples might be buried there that could be included in that park. The deepest and commonly most striking glacial striae and polish are those on dolomite or limestone, but to be preserved they must have been under several feet of soil since they were made. This means that only recent excavations will show them, for solution by rain destroys them in a few years. Once exposed they should be protected from the elements if they are to be preserved with all their original gloss. The Silurian dolomite (Fig. 3) is a logical place to look for them, and the escarpment in the vicinity of the Northern Kettle Interlobate Moraine should provide an excellent location. The Valders quarry, the type locality of the Valders drift, lies only 20 miles north-northeast of the present Northern Kettle Moraine State Forest and displays striae at right angles which can be correlated with two distinct tills, Valders and Cary. Regrettably, quarrying operations are fast removing them. Sites with two sets of striae probably are available closer to the forest, but I made no search for them.

Fossil periglacial phenomena are widespread in Wisconsin, but good sites are rare and almost inevitably are destroyed quickly. Most are found in artificial excavations, such as road cuts, borrow pits, and the like and are quickly covered over. Of the various kinds of features (Black 1964a) the most striking and important as paleoclimatologic indicators are ice-wedge casts (Black 1965). Sites relatively close to Mill Bluff or Bloomer have been found, and hopefully one at least could be made suitable for presentation to the public. These are in unconsolidated material and require protection from the elements to survive. Because they are so scarce and difficult to preserve, at least one site should be set aside for the future.

The Great Lakes history is a complicated and fascinating part of the Pleistocene. Part of the evidence is demonstrated at Two Creeks in the form of deposits, but no actual beaches are preserved there. Shorelines and shoreline phenomena are recorded at several places in southeastern Wisconsin, near or on the present shoreline of Lake Michigan. A swamp deposit with many kinds of wood dating about 6340 years B.P. is found at water level under dune deposits at the south city limits of Kenosha. The Glenwood and Calumet beaches can be traced almost continuously along that shore from the Illinois State line northward to Windy Point, north of Racine (Goldthwait 1907). Superb beaches may be found from present lake level to a height of several hundred feet above Lake Superior, between Superior and the Michigan border. Some can be correlated across or around the Bayfield Peninsula; higher, older beaches cannot be traced across, suggesting that individual lakes were established on east and west sides that were independent of each other. The Lake Superior beaches are independent of the Lake Michigan beaches and a site on either or both might be desirable.

Although occasional fragments of bone or teeth of Pleistocene mastodon or mammoth continue to appear, no complete skeletons have been found for many decades in Wisconsin. A reconstructed skeleton of a mastodon is mounted in the small museum of the Geology Department of the University of Wisconsin, Madison. That specimen, almost completely intact, came from the Wisconsin River deposits near Boaz, Richland County. Such a skeleton at a museum at the Natural Bridge and Rock Shelter would be most appropriate. Specimens of beaver-cut wood, such as have been found in the Wisconsin River deposits near Portage and dated at 6070 radiocarbon years B.P., could be added to such a museum along with other "finds."

West Blue Mound is already a state park, and East Blue Mound has a small county park on its north side. These two mounds provide an excellent view of the "Driftless Area", contain abundant block fields of chert rubble considered to have moved under periglacial climates, and provide us with the problem of explaining how soft shale and thin seams of dolomite of the Silurian formations (Fig. 3) can cap an upland surface which is above several supposed peneplains (Black et al. 1965:56-81). Here is a natural setup for examining some of our basic tenets in geomorphology as affected by the various forms of weathering and erosion during the Pleistocene.¹

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¹See Univ. Wis. Geol. and Nat. Hist. Sur. Info. Circ. No. 15.

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Last but not least of interesting places especially singled out for mention here is the Wisconsin Dells. Now almost 100% commercialized, it is out of the question to purchase it. Nonetheless, as an example of drainage diversions produced during the Ice Age it is excellent (Martin 1932:345-353; Powers 1946).