Day, M. Caves in the Driftless Area of Southwestern Wisconsin

CAVES IN THE DRIFTlESS AREA OF SOUTHWESTERN WISCONSIN

Michael Day Univeristy of Wisconsin-Milwaukee

The Driftless Area of Southwestern Wisconsin contains a wide variety of ka r s t landforms, including hundreds of kilometers of dry and ephemeral v~IIeys, several hundred sinkholes and some 200 caves. Althou9h t he caves are small and not much challenge to sporting cavers, they are of cons ide rable geographical Interest since they provide information not only about karst development in the Driftless Area but also about the area's geomorphological and climatic history (Day 1986).

SOUTHWEST WISCONSIN GEOMORPHOLOGY

Southestern Wisconsin is an upland cuesta dissected by dendritic dra inage (Figure I). North of the Wisconsin River interfluves are capped by Ordovician Pralrie"du Chien carbonates. Sinnipee Group carbonates cap most ridges south of the river (Figures I & 2). Ridge tops are fla t or gently sloping but valley side slopes are steep with cliff faces developed in the carbonates. The valleys themselves are deep, broad, and alluviated. Local re lief averages between 50 and 120 m/km2 (Knox 1985). Massive erosion of the valleys occurred during the Pleistocene either by glacial meltwater or by river eros ion during wetter episodes. Palmquist (1965) concluded that the present drainage configuration was established prior to the Illinoian, and Frye (1973) and Frye et al (1965) suggested that maximum entrenchment had occurred during the Kansan. Mickelson et al (1982), on the basis of Nebraskan deposits in the Wisconsin River Valley postulated entrenchment of some ~5m since the Kansan. Mil ske et al (1983) showed that valley entrenchment in adjacent southeastern Minnesota comme nced at about 160,000 B.P. Marked incision and erosion of colluvial and fluvial sediments was also triggered by release of glacial lake waters which occurred at about 12,000 B.P. (Knox et al 1981; Clayton 1982) and may have continued until about 9500 B.P. (Knox 1982). Several cycles of valley aggradation are indi­ cated and main valley floodplains are as much as 50 to 75m above bedrock va lley floors (Frye et al 1965) . The beds of headwater tributaries rest On bedrock while those of trunk channels are on sandy gravels (Knox 1985). Terraced late Pleistocene and Holocene alluvial floodplain sediments whi c h Overli e the gravel fi II are Incised by laterally-migrating river channel s (Knox and Johnson 1974; Knox, 1972, 1980, 19HI). The re has been much debate about the Quaternary history of the Driftless Area. Outwash, lake deposits, and loess are present in Southwestern Wiscon s in (Fig ure 3). but mo s t writers have accepted that evidence of di rect glaciation in the Driftless Area is lacking and several hypotheses have been formul a ted

42 o 25 50 MI I~-Tj-J....j--"j---r-l,f - - KANSAN 25 50 75 KM o - - - NEBRASKAN FIGURE 1. GLACIAL BOUNDARIES AND DRAINAGE ,OF THE DRIFTLESS AREA.

to explain either why ice did not accumul ate o r why g lacial mater ials were not deposited. Several writers, e .g. Black 1960 et. s eq.). have ma intained that the Driftless Area was in fact glac iated during at least some phases of the Pleistocene. but the we ight of evidence opposes t his (Micke lson et al 1982).

GEOL OGY OF THE KARS T

The karst in southweste rn Wisconsin is developed in the do lom ites among the approxima tel y 400 meters of Paleozoic sedimentary rocks. The rocks general ly di p at less than I to the south and southwest (Barden 19B O) . ~ NIAGARA DOLOMITE D RICHMOND SHALE m GALENA DOLOMITE k';~ J ST. PETER SANDSTONE ~ PRAIRIE DU CHIEN E:i3 DOLOMITE F{"(::J CAMBRIAN SANDSTONE D DEVONIAN ROCKS 1 ' ; ' ::~1 PRE-CAMBRIAN ROCKS - DRIFTLESS AREA

o 50 MI I I I I o 50 KM

:« • • • • ••. . :Io~ . • ••• • •. • ~...... ::> ••. • •• • •• • • eta: •••• • • • •• ~ llI ~ :I FIGURE 2. BEDROCK GEOLOGY OF THE DRIFTLESS AREA.

The major karstic formations are the Ordovician carbonates: the dolomitic Oneonta formation of the Prairie du Chien Group and the Platteville and Galena dolomites of the Sinnippee Group (Figure 2). The Oneonta Do lomite is the lowest forma tion in the Ordovician Prairie du Chien Group. It is nearly 60m thick and consists of a grey-brown, variably bedded crysta lline dolostone with minor amounts of chert and shale. Locally there are poorly preserved algal stromatolites and large secondary calcite crysta ls. The Prairie du Chien generally is a medium-textured impure sandy do lom i te with a quartz content often in excess of 10% (Day 1979, 1984) and c lay cont en t s averag ing 2.1% (Frolking 1982) . Mean insoluble residue is 12.17% by we ight (Day 1979) with local range be tween 1.3% and 26.26% (B l ack 1970b) . 2

!::...:.: :....: : :~ OUTWAS H m:ttJ lACUSTRINE

- WISCONSIN

-­ KA NSAN

- _. NEBRASKAN o 25 50 MI ~I-----r-I---1.1----r­1 ­ -,-III o 25 5 0 75 KM

FIGURE 3. OUTWASH AND LACUSTRINE DEPOSITS IN THE DRIFTLESS ARE A. 46

The dolomites of t he Platteville Formation are up to 25m thick. The lowe st member. the Pecatonica, is overlain by the McGregor Member and by the upper member, the Quim bys Mill. All three are buff to blue-grey. fossil­ Iferous. thick bedded limestones and dolomites. The Galena Fo rma t ion i s the upper unit of the Sinnippee group. The three membe r s of the Galena. in ascending order t he Dunleith, Wise lake, and Dubuque. are va ri ably bedded . buff, sha ley dolomites locally wi t h chert and shale ba nd s. Tota l thi ckness of t he Galena is nea r ly 80m (Barden 1980) .

THE KARST AND CAVES

The ka rs t is a regolith-covered fluviokarst (Sweeting 1972) with a combi na tion of kars t and fluvial features. In addition to caves, the karst contains a variety of sinkholes, and many tri butary valleys have sinking s t reams an d epheme ra l fl ow. The Plattevill e and Galena dol omites are the dominant cave and karst fo rmi ng rocks south of the Wisconsin River (Deckert 1980). North of the Wi sconsin River most caves a re in the Oneonta Formation of the Pra irie du Chien group (Figure 2). Ea rly s tud ies of the caves and karst of southwestern Wisconsin include those by lange (190 9) , Martin (1932), Murrish (1871), and Strong (1877, 1882). Bretz (1938) d i scus sed cave s in the Galena Formation. Recent descriptions of ind ivi dual caves a re to be found in issues of The Wisconsin Speleologist and compi lati on s a re presented in the 1976, 1979. and 1980 WSS Hodag Hu nt Guide books and in Alexande r (ed ., 1980). All of the probab ly 200- pl us cave s In southwestern Wisconsin are small . None exceeds IOOOm in total passage length and the vast majority are un der SOOm. In part t his Is because t he dolomites disso lve slowly (Paull & Paull 1977; Day 1984 b) but most of the caves are located on hilltops or hillsides and represent remnants of formerly more extensive cave systems now dis­ membered by va lley incision. Vall ey inci s ion by glacial meltwater was rapid and the caves, which now occupy the ridges. are essentially abandoned phreatic tubes and mazes formed in the saturated or groundwater zone. After valley inci s ion and drainage the caves were left stranded in the vadose or unsaturated zone. Present hilltop catchment areas were too small to promo t e much in-cave s tream entrenchment. Many of the caves are at least partially blocked by breakdown material fallen from the cave roof and walls. The caves a re shallow and only rarely are they more than 10m below the ground. The rel a tionship of the caves to regional drainage patterns at their time of forma tion i s unknown since the caves are fragmentary. Pre-incision they were presumably draining toward the proto-Mississippi or its tribut ary, the proto- Wiscons in. Joint control has been important In formation (Olmstead and Borman 1968; Barden 1980) . Integration of the caves with present hydrology i s limited. Most passages receive onl y pe rcola t ion and a re dry except during periods afte r heavy ra in or during sp ring snow mel t. Ra re examples of in tegration are the meandering st ream-cut trench leading into Star Val ley Cave and the vadose sections in Cave of t he Mounds . 47

Severa l of t he caves have been discovered du r ing quarrying most notably Bear Creek Cave, in 1954 (Deckert 1980; Ehr 1976) , Cave of the Mounds, In 1939 (Barden 1980) , and Eys nogel Hili Cave, in 1964 (Boyd 1965). Add Itiona l ly, nineteenth cen tury lead mi ners Investigated seve ral of the caves, and Bogus Bluf f Cave was probably excavated In part. The no rmal a rray of cal c ite formations has developed in the caves and a few, i ncl ding Cave of t he Mou nd s and Eagl e Cave, a r e commercially operated. In most of t he non-commerc ial caves, most of the formations have been damaged by breakdown or vandalism and the rema ini ng in tact examples a re small and accessible only with difficulty. Si nkhol es a re characteristic f eatures of the ka rst of southwest Wis consin and several caves are en tered through the sides or bases of collapsed sinks. Several caves are deve loped adj acent to t he contact with the overlying rocks and some, including Sta r Valley, have ceiling exposures of the overlyi ng St . Peter Sandstone. Elsewhere , the overlying sandstones have collapsed Int o cavities in the Pra irie du Chien, producing sinkholes and caves such as Bridgeport Cave and Cobb Cave (Cronon 1970). Al t hough present day cave passages are small , usually requiri ng stooping or crawling, t hi s is a func t ion of t he la rge amounts of roof breakd own which all but fills many passages. Active breakdown occur s In several caves and large chambers, notably those in Boscobel Bear Ca ve , Pop's Cave, and Star Valley Cave, are floored wi t h breakdown s labs. Palmquist et al (1976), in northeastern Iowa, and Paull and Paull (1977) suggested that some Dri f t less Area caves were formed dur ing Pleistocene period s but Marti n (1932) fel t t ha t they were preglacial. The ir form s hows that most are clearly pre-W isconsinan and, by analogy with caves In glaciated areas of Europe, (e.g. Gascoyne and Ford 1984), almost certainly pre­ Ple i stocene. Cave systems In adjacent southeastern Minne sota may have been init iated as early as the Cretaceous (Wopat 1974). Al t ho ugh the development of southwest Wisconsin caves has not been exam i ne d In detail. it is possi ble to cons truct a genera l mod e l based on cave and other geomo rphologica l studies. Initial cave development predates valley entrenchmen t and was probably in t he shall ow phreat ic zone close to the level of satura t ion. Su rface val ley en trenc hme nt commenc ing at about 160 , 000 B. P. caus ed draining of t he caves and erosi on of sediment f il ls (Milske et al 198 3). A sequence proposed by Olms tead and Borman (1968) for Pop's Cave. may a lso represent a mod el of broad appli cabi lity. Pop 's Cave originated through bi-Ievel, j o i nt controlled phrea ti c solution contemporaneous with t he commencement of val ley Inci s ion to the nor th. As va ll ey downcu tting progressed. a major phase of forma t ion in t he upper par t of the phreat ic zone occurred as Inc reasi ng ly ag gress ive water came t hrough the cave. Furthe r va lley inc isi on then s tranded the bl- Ievel caves in the vadose zone and loss of buoyancy caused ceiling breakdown, t hrough which the lower passage eventually inter­ cepted the upper to produce the present configu ra t ion. A red clay characterizes the ca e of southwe s t Wisconsin and was me nt ioned by early writers such as Mar tin (1932). Olms tead and Borman (1968) 48

suggested t hat this clay infi 11ed Pop's Cave during the l ast stages of phreatic devel opment. and that an increase in the volume of clay toward the adjacent valley indica ted If •••a downward moveme nt of phreatic water and an increase in solution••• " (1968.123). It has often been a s sumed that the clay at one time a lmo s t comp letely filled the caves and, although Ehr (1976) suggested that the coni ca l c lay mound ca lled Mud Mountain in Bear Creek Cave wa s due to infil t ra t ion through a cei ing joint , the cl ay generally has been t houg ht to be t he wea thered residue o f t he ca rbonates themselves. The cave c lay i s similar to red clays whi ch mantle the surf aces of dolomite ridges . These cl ays are red to dark red-brown with minor yellow mot t l ings and grays prod uced by local reducing conditions. Frolking (1 98 2) and Fro lk i ng e t a l (1 983) s howed that the clays were not produced solely by we athe ring of do lomite o r Woodfordian age loess , but resulted from illuvi a tion of c lays In the zone of dolomite dissolution. Studies of the cave sed imen ts show that they are formed partly by weat her ing of the dolomite but are mostl y de ri ved f rom surface loess which ha s infiltrated into t he caves vi a fis s ures (Day 1986bj Bull and Day 1986). The absence of any depos its of di rec t g laci al ori g in, in combination with Uranium series dating of calcite depos i ts, indica t es t hat southwe ste rn Wiscons in was not glaciated at least duri ng the l a tter phases of the Pleistocene.

CONCLUDING REMARKS

Al t hough Wiscon sin Dr ift les s Area caves are not well known, t hey are numerous, var ied , and of cons i de rable geographica l interest. Studi es to da te s how t ha t the caves may revea l much a bout the Quaternary history of the Drift less Area, and hey are thus deserving of greater attention.

REFERENCES

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Barden, M.J., 1980. Geology Field Trip Guide. Wisconsin Speleological Society Hodag Hunt Guidebook, Section 2.

Black, R.F. 1960. I'Driftless Areal! of Wisconsin was Glaciated. Bull. Geol. Soc. America 71: 1827.

• 1964. The Physical r,eoQr~ p h y of Wisconsin. State of Wisconsin ~"""'B ":"'lue book 171-177.

• 1970a. Bl ue Moun ds and the Erosional Hi story of Southwestern --W:-:-:'"is con si n. In Pl e ist ocene Geology of Sou t hern Wisconsin. Wisconsi n Geo log ica l and Nat ural History Survey Informa tion Circular 15, HI - HII.

• 1970b. Res i duum and Ancient So i Is of Southwestern Wisconsin. In --=-~Pleistocene Geology of Sout hern Wisconsin. Wisconsin Geological and Natural History Survey Info rmat ion Ci rcul ar 15, 11 -112. Boyd, s. 1965. WSS to Establish Second Cave Preserve. The Wiscons in Speleologist 4: 7.

Bretz, H.H. 1938. Caves in the Galena Formation. Journal of Geology 46 : 828-841.

Bull, P.A. and Day, M.J. 1986. Cave Sed iments in the Driftless Area of Wisconsin. Oxford Geography Research Paper, in press.

Clayton, L. 1982. Influence of Agassiz and Superior Drainage on the Mississippi River. In Quaternary History of the Driftless Area. Wisconsin Geological and Natural History Survey Field Trip Guide Book 5: 83-87.

Cronon, W. 1970. The Sandstone Caves of Wisconsin. The Wisconsin Speleologist 9: 53-99.

Day, M.J. 1979. Preliminary Results of an Investigation of Current Rates of Erosion in the Wisconsin Karst. The Wisconsin Speleologist 16: 11-23.

__~_. 1984. Carbonate Erosion Rates In Southwestern Wi sconsin. Physical Geography 5: 142-149 •

• 1986a. Cave Studies in Southwestern Wisconsin: Imp lications and ---r-Importance. The Wisconsin Speleologist 19: 1-21.

---r-' 1986b. Caves in Southwestern Wi sconsin, U.S.A. Proceedings 8t h Interna tional Speleolog ica l Con gress, in press.

Deckert, G. 1980. Geo logy of Southwestern Wi sconsin. In An Introduction to Caves of MinnesotaL Iowa, and Wisconsin, ed. E.C. Alexander, pp. 109-110. N.S.S. Convention Guidebook 21.

Ehr, B. 1976. The Bear Creek Cave Report. The Wisconsin Speleologist 14: 1-17.

Frolking, T.A. 1982. The Genesis and Distribution of Upland Red Clays in Wlsconsin's Driftless Area. In Quaternary History of the Driftless Are~. Wisconsin Geological and Natural History Survey Field Trip Guidebook 5: 88-97.

Frol king, T.A., Jackson, M.L. & Knox, J.C. 1983. Origin of Red Clay over Dolomite in the Loess-covered Wisconsin Driftless Uplands. Soil Science Society of America Journal 47: 817-820.

Frye, J.C. 1973. Pleistocene Succession of the Central Interior United States. Quaternary Research 3: 275-283. 50

Frye, J.C., Willman, H.B., and Black, R.F. 1965. Outline of Glacial Geol ogy of I l l inois and Wiscons in. In The Quaterna ry of the United States , ed. H. E. Wr ight and D.G. Fr.ye, pp. 43-61. Princeton University Press.

Gascoyne, M and Fo rd, D.C. 1984. Uranium Series Dating of Speleothems, Part I I: Res ults from the Yorkshire Dales and Implications for Cave Develop­ ment and Quaternary Climates. Cave Science II: 65-84.

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• 1980. Wisconsinan and Holocene Valley Depos i ts In the Wisconsin - """":"Drl- f tless Area. Geol. Soc. America Abst. with Programs 12: 231.

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_~_ . 1982. Qua t e r nary History of the Kickapoo and Lower Wisconsin River Vall eys, Wisconsi n. In Quaternary History of the Driftless Area. Wis con s in Geo log ica l and Natu ral History Survey Field Trip Guide Book 5: 1-66. • 1985. Re sponses of Floods to Holocene Climatic Change in the Upper --Mississipp.... i Val ley . Qua t ernary Research 23: 287-300. and John son, W.C. 1974. Late Quaternary Valley Alluvlatlon In the -~D-r i ft less Area of Sou thwestern Wiscons in. In Late Quaternary Environments of Wi scons in, ed. J.C.Knox and D.M. Mickelson, pp. 134- 162. Wisconsin Geo og ical and Natura l Hi s tory Survey.

, McDowell, P.F., and Johnson, W.C. 1981. Holocene Fluvial Stratlgr~phy ---and Clima t ic Change in the Driftless Area, Wisconsin. In Quaternary Paleocl ima te , ed. W.C. Mahaney, pp. 107-127. Norwich: Geobooks.

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Mickelson. D.M., Knox, J.C., and Cl ayton, L. 1982. Glaciation of the Drift less Area : An Eva lua t ion of the Evidence. In Quaternary History of the Driftless Area . Wiscon s in Geologica l and Na tural History Survey Field Trip Guidebook 5:155 -1 69. Milske. J.A., Alexande r, E.C. , and Lively. R.S. 19B3. Clastic Sediments in Myste ry Ca ve, Southe as tern Minnesota. N.S.S. Bulletin 45: 55-75. 51

Murrish, J. 1871. Re po rt to t he State of Wiscons in on t he Geo l09ical Survey of the Lead Reg ions.

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, Madenford, G.A., and Van Ori el , J.N. 1976 . Do l lne Densi ties i n --~Northeastern- Iowa. N.S.S. Bull e tin 38: 59-67.

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