Steven Dutch, Professor Emeritus, Natural and Applied Sciences, Universityof Wisconsin Green Bay
The 1980 guidebook is running low on remaining hard copies and seems to disappear from collections quickly. Therefore I have put it on line as a service to the geological community. Apart from changes needed to convert to Web format, and corrections to typographical errors, no changes have been made to the text. Figures have been scanned from the original guide but, apart from cleaning up lettering for legibility, have not been changed. The maps, which were photocopied from topographic sheets and are of marginal quality in the guidebook, have been redrawn from digital maps available on line from the U.S. Geological Survey. They match the originals as closely as possible but may contain later details not on the original maps. Geologists particularly should be aware that nothing is forever, and some stops have changed. They may have been built over, covered, excavated, or no longer be accessible. This guidebook does not imply permission to enter localities on private land.
|Geology of eastern and northeastern Wisconsin |
A guidebook for 44th Annual Tri-State Geological Field Conference
October 11-12, 1980
Edited by Ronald D. Stieglitz
Paula E. Allen, University of Wisconsin-Green Bay
Sponsor: Earth Science Discipline, University of Wisconsin-Green Bay
University of Wisconsin-Green Bay
Green Bay, Wisconsin 54302
Office of the Chancellor
Greetings to Tri-State Participants:
The University of Wisconsin-Green Bay is young, as universities go. It began officially in 1965, when the Wisconsin legislature authorized a new campus of the University of Wisconsin for northeastern Wisconsin. The first students enrolled in September 1969.
UWGB's newness and the times when it was founded provided the opportunity to plan a university that combines two traditions in higher education; the tradition of a. Liberal arts college and the tradition of a land-grant university--a university with special meaning for the last decades of the 20th century. As such, UWGB has been assigned a special mission to provide an educational program that is substantially different from that of any other University of Wisconsin system unit--a university concerned with the problems of people and their environment.
Our special mission is fulfilled through a variety of problem-focused, interdisciplinary programs. Additionally, we offer the more traditional disciplines. A special feature of our educational plan is an emphasis on community issues and field studies.
Our 600-acre campus, sloping from the Niagara escarpment to the waters of Green Bay, and located above a glacial-age buried forest, is a most appropriate site for your gathering. It is therefore obvious that we at UWGB feel warmly toward those with geological interests. Given the UWGB emphasis on the problems of the environment, geology is of necessity an important interest to our students, to our faculty, and in our academic plan.
Thus it is with pleasure that I welcome the 44th Annual Tri-State Geological Field Conference to the University of Wisconsin-Green Bay. Thank you for coming. And please feel free to visit us again, soon and often.
Edward W. Weidner
Sincere and warm thanks are offered to all the individuals and organizations who have helped plan and successfully conduct this the 44th annual tri-state field conference. Special recognition is due: the contributing authors and field trip leaders; Joseph M. Moran, chairman of the earth science discipline at the University of Wisconsin-Green Bay for organizing and carrying out most of the administrative details; Robert B. Wenger, past chairman, and our other colleagues in the Science and Environmental Change concentration for support and encouragement; the Wisconsin Geological and Natural History Survey for supplying geologic, glacial and landform maps included in the guidebook and other assistance; Donald j. Johnston for much of the guidebook drafting; William D. Newcomb and other members of the UWGB earth science club for many kinds of help; the owners and managers of the quarries and pits visited for granting us access; Edward R. May for his presentation following the banquet. We also gratefully acknowledge the Green Bay visitors and convention bureau and the University of Wisconsin-Green Bay Office of Outreach, particularly Jan Thornton, for invaluable advice and assistance. Finally, a very special thanks to Joy Phillips, who patiently and, usually cheerfully, typed the many drafts of the guidebook.
Ronald D. Stieglitz, University of Wisconsin-Green Bay
Interesting geological features and unsolved geological problems abound in eastern and northeastern Wisconsin. A great variety of Precambrian rocks compose the still poorly understood, basement complex of the Wisconsin dome. Sedimentary rocks deposited in shallow platform seas of the Paleozoic now dip gently eastward and southeastward into the. Michigan basin forming a series of west facing escarpments. Excellent examples of glacial landforms are common throughout the region and vividly document the effects of the late Wisconsin ice sheets. Investigations of these, rocks and glacial materials in northeastern Wisconsin and elsewhere in the state contributed, among other things, to deciphering Precambrian history and economic geology, a better understanding of Paleozoic stratigraphy snd patterns of sedimentation on the north American craton, the concept of organic reefs, and the development of the idea of continental glaciation.
First native copper and later iron ore provided the impetus for the study of the Precambrian rocks of the Canadian shield in upper Michigan and northern Wisconsin. Economic factors, thick overburden, and a difficult terrain of forests, swamps, and lakes combined to delay mapping and thorough geological exploration of the area. Recently, interest in these ancient rocks has been renewed by the search for and discovery of sulfide mineral deposits. Modern techniques of mapping and exploration such as satellite imagery, and aerial magnetic or gravity surveys together with detailed ground investigations and drilling programs hold promise for a more complete understanding of the complex relationships with the Precambrian rocks (Van Schmus and others, 1975; Sims, 1976).
The framework of the Paleozoic sequence was established quite early. Studies by Chamberlin (1877), Steidtmann (1924), and Schrock (1939) each describe rocks from the northeastern or eastern part of the state, however, few recent detailed reports of the rocks or fossils of the area have been published. Clark (1971) reported on biostratigraphic work in the Wisconsin Paleozoic section based on conodonts. The bulk of the Paleozoic section is composed of sandstones and dolomites with the notable exception of the Maquoketa formation which contains much clay apparently derived from an eastern source. These rocks, particularly the dolomite units have long been used for crushed stone, building stone and in some cases lime. The stratigraphic terminology used in this guidebook follows Ostrom (1967).
A long interval of unrecorded time separates the Paleozoic rocks from the overlying glacial ro.aterlal3 which were deposited as tongues of ice pushed down the lowlands, now occupied by Green Bay and lake Michigan, and across the northern highlands. Eroslonal features as well as moraines, drumlins, kames and ice fill features were created in abundance. During periods of recession, water impounded in front of the ice filled large lakes particularly in the Fox River valley.
Many geologists including Chamberlin (1877), Thwaites (1943), Thwaites and Bertrand (1957) and Black (1970) investigated the glacial landforms and materials and contributed greatly to the understanding of Pleistocene history. Recently, attention has been directed toward working out the detailed glacial stratigraphy of the region with results leading to suggestions for the revision of the established terminology of the late Wisconsin (Evenson, 1973; Evenson and others, 1976).
The soils of the region have formed in transported materials except the cumulose organic soils and as a result closely reflect the glacj landforms and materials (Link and others, 1974; Otter, 1980). Till, wash, and glacial lacustrine sediments are the dominant parent matoi a thin layer of loess, less than 15 cm in most areas, mantles the uplands.
The distribution of sand and clay in the parent materials was influenced by the bedrock rock overridden by the ice and the specific mechanism of glacial or related deposition. Soils of the northern and western portion of the area are sandy being formed in till and outwash derived from Cambrian sandstone and St. Peter sandstone. The eastern and southern portions of the area are dominated by soils formed on clay rich tills. Fine soils also are found in the lake plains of the central part of the area except where beach ridges and sand bars developed. The landscape is relatively young with imperfect drainage and a large number of pot hole lakes, bogs and marshes, or remnant wetland organic soils areas are present. The time for soil development has been rather short, less than 11,000 years and hence the soils are at a relatively young to early medial stage of development.
The interrelationships of bedrock, topography, glacial history and soils are close in northeastern Wisconsin. The remainder of this guidebook will provide more detailed information on some of these connections. Specifcally, field trips will explore part of the Precambrian basement complex northwest of Green Bay in Oconto and Marinette counties, and the glacial stratigraphy and terminology questions of eastern Wisconsin. Other field trips or parts of field trips will touch on the Paleozoic rocks, environmental concerns, geomorphology and soil of the area.
Steven I. Dutch, College of Environmental Sciences University of Wisconsin-Green Bay, Green Bay, Wisconsin 54302
It is probably accurate to state that some of the largest blank areas on geologic maps in the U.S. occur in northern Wisconsin, where Precambrian rocks of considerable complexity are concealed by thick Pleistocene deposits. Mapping of these areas is now being done geophysically, using well samples and outcrops for control. In recent years there has been a resurgence of interest in the Precambrian of Wisconsin, accelerated by the discovery of several massive sulfide deposits.
|Approximate Age||Event||Representative in Mountaln-Crivitz area|
|1100||Keeweenawan rifting||none known|
|1450-1500||Intrusion of Wolf River Batholith||Belongia Granite, Hagar Intrusives Peshtigo Intrusives|
|Deformation and Metamorphism; Sandstones metamorphosed to quartzites|
|Quartz sands deposited||McCaslin, Thunder Mountain Quartzites Baldwin Conglomerate|
|Penokean Orogeny 1850 m.y.||Block faulting and cataclasis, deformation and metamorphism, intrusion of granitic plutons||Athelstane quartz monzonite McAuley gneiss?|
|1900 m.y.||Volcanism||Waupee Volcanics|
|2500 m.y.||Formation of superior province granite-greenstone belt terrains||none known|
|2500-3000 m.y.||Formation of migmatite-gneiss complex||none known|
Figure 1. Bedrock geology of the Mountain-Crivitz area (above) geology from Medaris and Anderson (1973). Field trip stops are numbered.
The oldest rocks of Wisconsin are of Archean (Precambrian W) age and represent a southern extension of the superior province of the canadian shield. In the U.S, two subprovinces can be recognized: a granite-greenstone belt terrane on the. North and a migmatite-gneiss terrane on the south. The dividing line runs across central Minnesota, northwestern Wisconsin and the upper peninsula of Michigan, so that most of Wisconsin lies in the migmatitegneiss subprovince. This subprovince has yielded extremely high ages: 3600 m.y. from the Minnesota river valley. The highest ages yet recorded in Wisconsin are 2750 m.y. from west-central Wisconsin (Van schmus and Anderson, 1977). No known Archean rocks occur in the mountain-Crivitz area.
The Archean rocks are overlain by middle Precambrian (X and Y) metavolcanic and metasedimentary rocks. These rocks underwent metamorphism. Intrusion of granitic plutons and deformation during the Penokean orogeny about 16001800 m.y. Ago. This terrane correlates with the southern province of the Canadian shield, which might better be called the Penokean province. (on the map of Rudman and others, 1965, the "southern" province lies north of the "central" province!) The Waupee Volcanics, Athelstane quartz monzonite and mcauley gneiss are representatives of this episode in the Mountain-Crivitz area.
The Precambrian X metavolcanic rocks are the host rocks for the recently discovered stratiform massive sulfide deposits (figure 2). The largest of the deposits is at Crandon, where an estimated 70 million tons of ore containing 5?o zinc and 17, copper occur in a steeply-dipping lens 5000 feet long, 100 feet wide and 1650 feet deep (all data on these ore bodies compiled by mudrey, 1976). The next largest, deposit is at Ladysmith, where 4-6 million tons of ore averaging about 3.5-4% copper occur in a body almost exactly half the dimensions of the Crandon body. The smallest of the ore bodies, at pelican river, contains about 2 million tons of ore in a lens 1000 feet long, 50 feet wide and 650 feet deep. The ore contains 4.5% zinc and 17% copper.
Figure 2. Location of major massive sulfide deposits in Wisconsin. L = Ladysmith, p == pelican lake, c = Crandon. Metavolcanic rocks are stippled; Waupee Volcanics are solid black.
The similarity of the ore bodies is remarkable. All are steeply dipping lenses of similar proportions, all have been dated at 1820 to 1835 m.y., and all occur as stratiform deposits in tuffaceous intermediate to felsic volcanic rocks. The only major point of difference is in the metamorphic grade of the volcanic rocks. Those at Crandon are low greenschist facies whereas those at pelican lake are middle amphibolite (slllimanite-cordierite-muscovite subfacies). Crandon and Ladysmith both have extensive supergene enrichment to 150 feet.
Start-up of mining operations has proceeded slowly, hampered by environmental concerns and uncertainties about taxation. A major environmental concern is that the Crandon ore deposit lies near the headwaters of the Wolf River, and improper disposal of mining wastes could pollute the entire wolf and lower Fox Rivers. An additional concern is what will happen when mining operations end. The projected life of the Crandon ore body is about 25 years, that of the Ladysmith deposit somewhat less. There is concern that mining could spur temporary prosperity, but lead to economic depression in the area once the mines close. The supergene-enriched parts of the Crandon and Ladysmith deposits would be highly prized mining targets, but mining that part of the Crandon ore body would entail an open pit mine in addition to the projected underground mine, and the concern over impact of such open pit mining is great. The small size and less sensitive location of the Ladysmith deposit make open-pit mining there a less volatile topic.
The metavolcanic rocks in which all three of these ore bodies occur cover a large portion of northern Wisconsin. The representatives of this metavolcanic belt in northeastern Wisconsin are the Waupee Volcanics. Although there are no major sulfide deposits known at present in this area, the Waupee Volcanics are otherwise, fairly similar in lithology and structure to the ore-bearing rocks further north and west.
Block-faulting played a major part in Penokean tectonism (Laberge, 1976) cataclastic rocks have been found in many parts of Wisconsin. None are presently known in the Mountain-Crivitz area, however.
A prolonged episode of erosion and deposition of pure quartz sands, folio by deformation and metamorphism, produced extensive quartzites in Wisconsin (figure 3). These are Precambrian Y, and probably correlate with the well known Sioux quartzite of Minnesota and South Dakota (Dott and Dalziel, 1972). The best known of these units is the famous Baraboo quartzite. I the Mountain-Crivitz area, the McCaslin and Thunder Mountain quartzites, and perhaps the Baldwin Conglomerate, represent this episode.
Figure 3. Middle Precambrian quartzites in Wisconsin.
The Baraboo, McCaslin, Thunder Mountain and Rib Mountain quartzites are thick, steeply-dipping units. The Necedah and Watertown quartzites are positionally similar but either of unknown attitude (Necedah) or gently dipping (Watertown). All these rocks are very pure; the Baraboo, Necedah and, in part, the McCaslin quartzite are generally red to purple from iron staining; the other quartzites are mostly white or gray and very coarsely crystalline. A curious feature shared by most of them is the presence o: one or more zones of quartz-vein brecciation, which consists of angular fragments loosely packed in a quartz matrix, commonly with crystal-lined voids. The similarity of these breccias from one unit to the next is striking.
The structural setting of several of these quartzites is also strikingly similar. The Baraboo syncline is well known. The McCaslin and Thunder Mountain quartzites have been interpreted to mark the northern limb and nose of a large synform (Mancuso, 1960). Smith (1978) has suggested tha the exposed Watertown quartzites, together with other occurrences known from well data, form an east-plunging syncline. Finally, the Rib Mountain and several nearby smaller quartzite bodies have been interpreted as downdropped blocks in a ring complex (Laberge and Myers, 1973). Thus, four the major quartzite localities in Wisconsin occur in structural downwarps or depressions.
The other quartzites differ in texture and composition. Whereas the units named so far are all massive or thick-bedded, the Hamilton Mound, Powers Bluff and Barron quartzites are rather thin-bedded and much less pure, i show a considerably greater color variation.
It is tempting to correlate all the quartzites, or at least all the thick, pure quartzites, and there seems to be little pressing reason not to do so. The Baraboo and Watertown quartzite overlie the 1800 m.y. Old rhyolites of south-central Wisconsin (Smith, 1978; van schmus, 1978) and are overlain by other Precambrian sedimentary rocks and Cambrian sandstones (Dalziel and Dott, 1970). The Rib Mountain quartzites are intruded by the 1500-m.y.Wolf River batholith as are the Thunder Mountain and McCaslin quartzites there is thus no conflict in correlating them, but some caution seems advisable.
The genesis of the quartzites is perplexing. The sedimentary environment of the thick orthoquartzites was probably a tectonically quiet one in which prolonged weathering and reworking took place, rather like the environment which the Cambrian sandstones of Wisconsin and the Ordovician st. Peter sandstone formed. However, the Precambrian quartzites are extremely thick. The nearly vertical Rib Mountain quartzite measures nearly a mile across strike, the similarly steep McCaslin quartzite almost two miles in place the inferred thickness of the Baraboo quartzite in several places is over a mile (Dalziel and Dott, 1970, plate ii). It is hard to envision a uniform blanket of pure quartz sand accumulating to such thicknesses over much of Wisconsin. It is also hard to envision the alternative; collection of large amounts of hypermature sediments in subsiding basins without a considerable admixture of less mature sediments. Perhaps some of the observed thickness may be due to deformation, but some form of subsiding-basin interpretation seems necessary as well.
The major structure in the Mountain-Crivitz area is believed to be a tight steeply westward-plunging syncline, the McCaslin syncline. The most conspicuous marker of this structure is a quite pure quartzite, which outcrops on McCaslin mountain, the north limb of the fold, and Thunder Mountain, the hinge area. Mancuso (1960) considered a small quartz-pebble metaconglomerate lens, the Baldwin Conglomerate, to be equivalent, to the McCaslin quartzite and to form the southern limb of the fold. The general strike other bedded rocks in this region, notably the Waupee Volcanics, is in reasonable agreement with the synform concept. There seems little reason to doubt about the correlation of the McCaslin and Thunder Mountain quartzites, though the correlation of the Baldwin Conglomerate may be questionable. The detailed analysis of the McCaslin syncline is hampered by a general lack of minor deformation structures related to the larger structure and the absence of clear facing criteria in the metasedimentary rocks.
Intrusive rocks cover most of this area. Most of the interior of the syncline is occupied by fine-grained porphyritic felsic units which Mancuso called Hagar rhyolite but which have since been reclassified into several intrusive units, most of which still retain the name "Hagar." these rocks are now considered to be part of the Wolf River batholith (Medaris and others, 1973).
The Wolf River Batholith covers at least 3600 square miles and is an anorogenic, high-level intrusion about 1450 to 1500 m.y. Old. Most of the exposed intrusive rocks of the Mountain-Crivitz area are part of this complex. Most of this batholith is made up of coarse porphyritic granite, often with rapikivi texture. Several ring complexes occur in central Wisconsin along the western margin of the batholith. Rib mountain, one of the major quartzite monadnocks of Wisconsin, is one of a series of quartzite inclusions around the margins of one of these ring complexes.
Although the geometry of the mountain area is not as neat as that of the ring complexes of central Wisconsin, the rock units in this area led Medaris and others (1973) to suggest that the rocks of the mountain area formed part of a ring complex. Is the McCaslin "syncline" actually the collapsed roof of a ring complex?
The last major Precambrian event in Wisconsin was a remarkable rifting and volcanic episode about 1100 m.y. Ago which formed the Keeweenawan complex (Craddock, 1972). The subsurface continuation of this complex, the Midcontinent Gravity High (King and Zeitz, 1971) extends from Kansas to Lake Superior, then southeast under Michigan. It has no presently known expression in northeastern Wisconsin.
Created 25 August 2004, Last Update 13 January 2020
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