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

Drumlins have been by far the longest known and best known streamline molded forms (Flint 1957:66). Charlesworth (1957:389-403) lists 302 citations to the literature extant at the time, and many other papers on drumlins have appeared since. To this day the origin of drumlins remains conjectural, only in part because different streamline molded forms are called drumlins. Alden (1918:253-256, Pl. III) last mapped and described the drumlins of southeastern Wisconsin where about 5000 drumlins are recognized (Fig. 38). Drumlins and drumlinoidal ridges and flutings in the Campbellsport area (Figs. 1, 2, 4, 39) were included on Alden's geologic map, but not specifically mentioned in the text. Neither were they among those mapped and described in an earlier report (Alden 1905) which still provides us with the bulk of our information on the drumlins of Wisconsin.

Fig. 38. Drumlins of southeastern Wisconsin. After Alden (1918) via Prouty (1960, Fig. 7).

Alden (1918:253-255) wrote:

The writer prefers to restrict the name drumlin to those drift hills which show clearly the molding effect of the advancing ice. The typical drumlin of southeastern Wisconsin may be said to be a hill of glacial drift which approximates the form of a segment of an elongated ovid, of which the widest part of the basal outline and the highest point of the crest are generally not more distant from the stross end than one-third the length of the major axis, and whose major axis is oriented parallel to the direction of the movement of the glacier which formed it. From this type the forms vary on the one hand to elongated narrow ridges, some of which attain lengths of 3 to 4 miles, and on the other hand to nearly equiaxial dome-shaped or mammillary hills. Exceptional variations are double-tailed and double and triple crested forms, and ridges with subordinate crests overlapping in echelon. The longer forms were developed principally in the region of axial movement of the glacier and in the tract west of the Niagara escarpment, where there was good opportunity for the incorporation of sticky aluminous clay derived from the Cincinnati shale [part of Maquoketa, Fig. 3]. The presence of the adhesive clay doubtless facilitated the building up of drumlins by the plastering-on process, and the elongation of the forms may be some function of the more rapid movement along the Winnebago-Rock River trough. There is a general shortening of the forms progressively toward the limit of the advance, where the rate of flow was retarded owing to the thinning and wide radial spreading of the moving ice. The shortening of the forms on the upland east of the Niagara escarpment may be due to the retarding effect of this escarpment on the ice overriding it in addition to that resulting from thinning and radial spreading.

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With but few exceptions the partial sections of drumlins seen by the writer exposed compact structureless clayey till like that composing most of the rest of the ground-moraine deposit over the limestone areas. In some places the till is semistratified, with somewhat indefinite bands that curve conformably with the surface contours and suggest that the hill has been built up by the addition of more or less definite layers.

Layers of stratified sand and gravel or stoneless silt are exposed in sections of few drumlins. These are in some cases folded, and it is not clear that they have any definite relation to the drumlin structure as such.

A fairly definite cleavage in the clayey matrix of the till developed parallel to the curved surface suggests the effects of pressure of the overriding ice but may in reality be the result of successive additions of thin layers of adhesive clayey material. . . . Evidence indicating the absence of rock cores from the drumlins has been collected throughout the whole drumlin area.

. . .

Estimates based on pebbles collected from drift composing drumlins show . . . that about 91 per cent of the coarser material is of local derivation. If the analyses included also the finer material comprising the matrix of the till the percentage of local material present might be found to be even larger. This high percentage of local material indicates that the drumlins are composed of drift accumulated at or near the base of the ice and transported for comparatively short distances.

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The drumlins were formed . . . in those parts of the area of the Green Bay' Glacier where the lines of movement were radiating very notably as the ice spread to the curved margin of the lobe. The lines of movement bounding any drumlin-forming segment of this glacier from the north limit of the drumlins in the area of that segment to the peripheral margin of the lobe show that the amount of this spreading is very considerable—much greater than that which took place in similar segments of the glacier of equal initial width but within whose area no, or few, drumlins were formed. This relation gives rise to the suggestion that radiation was an important factor in drumlin formation. . . .

On Alden's map (1918, Pl. III) distinction was made between drumlins according to the description above and drumlinoidal ridges and fluted forms of similar shape and dimensions. No list of criteria distinguishing between the two were set up, although such forms with bed rock cores seem automatically to be called drumlinoidal. Such practice is generally, but not universally, followed today. Obviously by surface inspection alone, it is not always possible to distinguish true drumlins in Alden's sense from drumlinoidal ridges and fluted forms, and I make no pretext of doing so. Stratification of till (non water-worked) and drift (water-worked) in drumlins in Wisconsin seen by me is much more complicated than Alden described, but details cannot be entered here.

The specific drumlins and drumlinoidal forms of the Campbellsport area doubtless were specified in the Act because of their proximity to the Northern Kettle Interlobate Moraine rather than because of their uniqueness or unusual degree of development. The best drumlins (including drumlinoidal forms) in the vicinity of Campbellsport are centered 4 miles northwest of that town (Fig. 39). There the drumlins are generally 60-120 ft high, rounded, irregular, to elliptical. Elongation ratios commonly are less than 2:1. Some of the drumlinoidal forms are believed to have bedrock cores. The more symmetrical and elliptical drumlins clearly show deployment of the ice, but only minor flutes on the irregular forms show it.

Fig. 39. Part of U.S. Geological Survey Topographic Quadrangle—Campbellsport, showing general areas of drumlins recommended for the Reserve. Possible waysides are shown with black dots. Scale 1 mile per inch.

The Campbellsport drumlins, although typical of many in Wisconsin, are neither the highest, longest, largest, nor most symmetrical. They are closest to the Northern Kettle Interlobate Moraine and provide good views of such features from county roads not heavily traveled. In the area of better drumlins and drumlinoidal forms shown in Fig. 39 are some locations of possible roadside overlooks, not all of which are needed to give the visitor a good view of the drumlins. Typical views of the Campbellsport drumlins, from some of the recommended overlooks, are recorded in Figs. 40-42.

Fig. 40. View eastward of the long-profile of the drumlin with an elevation of 1123 ft, centered at the corners of secs. 9, 10, 15, and 16 (Fig. 39). The steeper stross (up ice) side shows clearly on the left.

Fig. 41. View southeastward of the cross-profile of the drumlin in the north-central part of sec. 10. Camera position is on County Highway Y, in the saddle in the SE1/4 SW1/4 sec. 3 (Fig. 39).

Fig. 42. View north-northwest of cross-profile of the drumlin in the center of sec. 28 as seen from the possible overlook on the town road, 0.25 mile west of the southeast corner of that section (Fig. 39).

Inasmuch as most of these drumlins seem to be composed of the pale yellow-brown sandy calcareous till typical of the drumlins and ground moraine over a broad area of the northern part of Green Bay Lobe, it is not likely that many would be destroyed if they were not in public ownership. The till makes good farm land, a relatively firm base for construction, but is only poorly suited for construction aggregate. Con sequently, available funds should go mainly toward acquisition of land associated with the Northern Kettle Interlobate Moraine, Devils Lake Park, and the Bloomer Moraine. Two or three of the proposed road sides shown in Fig. 39, for views of the drumlins, seem sufficient to me to integrate these features into the Reserve.

Larger, well-developed, rounded drumlins may be seen readily from State Highway 23, County Highway AA, and connecting town roads about 5 miles east of Fond du Lac (Figs. 4, 43). Elongated drumlins, with ratios of 5-10:1, are well displayed in the area south of Mayville and south and east of Horicon (Figs. 4, 44). Many drumlins south of Juneau and southwest of Beaver Dam are even more elongated and larger (Figs. 4, 45). Drumlins are less well developed in northern Wisconsin.

Fig. 43. Part of U.S. Geological Survey Topographic Quadrangle—Fond du Lac, showing drumlins.

Fig. 44. Part of U.S. Geological Survey Topographic Quadrangle—Horicon, showing drumlins. Scale 1 mile per inch.

Fig. 45. Part of U.S. Geological Survey Topographic Quadrangle—Beaver Dam, showing drumlins.

Fabric studies of the stones and finer particles in the till in the drumlins in Wisconsin have not been attempted. Few mineralogical and textural data are available. Obviously much subsurface geological study is needed to describe the drumlins adequately and to reconstruct their possible origin.