A diverse set of geomorphic or land-shaping processes acting on long-standing geologic and structural patterns have shaped the Niagara Escarpment.These processes vary in timescale, impact, and activity, and are frequently interrelated.The rocks of the landform were originally deposited in a subsiding basin in the Silurian sea and subsequently have been altered by climate and climate-dependent processes, such as running water, ice, groundwater, mass wasting, and the waves and currents of glacial and post-glacial lakes.The escarpment's form reflects the complex climatic and geological processes that have sculpted it over time.

The Niagara Escarpment and its adjacent cuesta formation form an approximate 650-mile-long corridor that traces the outer edge of the ancient Michigan Basin.While this geomorphologic feature straddles numerous political divides, it ties together the entire Great Lakes system, as no single lake is more than 50 mi (80 km) away from the escarpment's majestic cliff faces.This "Great Arc" creates and influences a terrestrial environment like no other feature of similar size in the world.This international-scale corridor contains a variety of geologic and biotic resources along its extent that expresses its uniqueness-and generates intrigue-like no other geologic feature in the Midwest.This paper provides the reader with an overview of the Niagara Escarpment resource under the context of the Great Arc and discusses past and current education and protection efforts by both government and non-government entities as components of a broader "conservation geology" concept.The discussion surveys the potential for developing a formal conservation geology program (a Geopark) that spans the Great Arc, combining existing efforts into a more cohesive program for conservation awareness and action.

We used coupled modeling of gravity and aeromagnetic data to estimate subsurface structure along seven northwest-southeast profi les perpendicular to the Waukesha Fault and one north-south profi le (tie line).Study results showed the Waukesha Fault as a high-angle normal fault dipping southeast and having maximum vertical displacement of 560 m.The depth to Precambrian crystalline basement rock southeast of the fault (downthrown block) exceeds the total depth of water wells, with one exception, because of normal vertical displacement.Delineating the basement elevations in this area has implications for addressing geologic and groundwater-resource issues in southeastern Wisconsin.Data from well records constrained basement elevations for the profi le parts northwest of the fault on the upthrown block and elevations of the top of the Cambrian Mount Simon Formation on the downthrown block.Only the southernmost profi le contained data to constrain the basement elevations on the downthrown block; this profi le was used to calibrate density and magnetic susceptibility values for the study.We used basement elevations from the profi le models and well records to create a three-dimensional representation of the Precambrian basement surface, which appears complex on both sides of the fault.Comparison of the Precambrian basement surface from this study with a surface based on well record data alone illustrates the benefi t of incorporating data from potential fi elds modeling for the delineation of subsurface structure.

Florence Bascom (1862Bascom ( -1945) ) was a petrologist and field geologist at Bryn Mawr College who provided a basic description and interpretation of major areas of Pennsylvania and surrounding regions.This paper is the first of a two-part study that explores the question of how Bascom became a geologist.The initial phase of this process took place in Wisconsin, to which she moved at the age of twelve when her father became president of the University at Madison.Both of her parents supported women's education, rights, and suffrage.Bascom graduated from the coeducational university in 1882 and, in a series of fits and starts in which scientific study alternated with social pleasures and non-scientific pursuits, she began to take a serious interest in geology.In 1883-84 she studied under two well known geologists there, Roland D. Irving and his student Charles R. Van Hise, obtaining a B.S. degree.Although she did not participate in field work, she conducted laboratory research on the gabbros of Lake Superior using the petrographic microscope

Volume 14 iron.Although the mechanical accretion of iron minerals is not ruled out, we consider it a less attractive theory than replacement.Hence, the mechanism and timing of replacement remains unresolved.Localized accumulation of ferruginous silt and clay resulted in the formation of a thin, dense, iron-rich layer at the top of the Neda Formation at the type area.Transgression of the Early Silurian sea over an irregular Ordovician surface resulted in deposition of the Mayville Dolomite prior to

The Precambrian terrane of the southern Lake Superior region records a long and complex geologic history.The oldest rock in the region was formed around 3.B to 3.6 Ga and repeated tectonic, igneous, and metamorphic activity continued throughout the Precambrian until about 1.1 Ga.Two contrasting Archean--aged geologic terranes are present.The first is an older southern gneiss terrane, parts of which were produced at least 3. B to 3.6 Ga.This terrane experienced regional metamorphic activity at approx imately 3.1, 2.6, 1. B, and 1. 6 Ga.To the north, a granite-greenstone terrane which constitutes the second and younger group of Archean rock was formed 2.75 to 2. 6 Ga.Archean metamorphism(s) in the gneiss terrane was relatively high grade (P = 5-6 Kb, T = 650-BOO OC), with some localized areas reaching the granulite facies.In contrast, regional metamorphism in the greenstone belts of the granite-greenstone terrane was low grade (P 3 Kb, T < 450 OC).LateArchean metamorphism in the southern gneiss terrane may be related to a collis ion event with the more northern granite-greenstone terrane.Early Proterozoic sedimentation, volcanism, and plutonism were extensive throughout much of the southern Lake Superior region, especially in Wisconsin.Metamorphism associated with the Penokean orogeny of 1.90 -1.BO Ga was wide spread and occurred mainly in the low-pressure to intermediate-to low-pres sure (P < 4 Kb) facies series, except for a possible belt of intermediate--pres sure facies series (P -7.5 Kb) kyanite schist in northern Wisconsin.The high est grade attained was the lower sillimanite zone, but much of the metamorphism reached only into the greenschist facies.Metamorphism at this time was con current with or preceded slightly the major deformational activity.At least two major phases of deformation can be recognized throughout the Lake Superior area.It is proposed that the metamorphism accompanying the Penokean orogeny can be interpreted in a plate-tectonic context.Medium-pressure kyanite schist in northern Wisconsin may represent a suture or mark the site of crustal collision_ Post--Penokean metamorphism around 1. 63 Ga also appears to be widespread, but is of low grade.Interpretation of the 1. 63 Ga metamorphism is complicated by the intrusion of the Wolf River Batholith and related rock (1_5 -1.45 Ga), which possibly produced widespread contact-like metamorphism in central and southern Wisconsin.The tectonic interpretation of the 1. 63 Ga event is uncer tain and widely debated at the present time.A possible, but presently unconfirmed pre-Penokean metamorphism around 2. 4 -2. 1 Ga is also obscured and complicated by younger tectonic and metamorphic events.

The McCaslin Formation of northeastern Wisconsin overlies the Waupee Volcanics and has been intruded by the Hager Rhyolite Porphry and High Falls Granite of the Wolf River Batholith.The McCaslin Formation is at least 1,220 m thick, consisting of a thin, basal quartz-pebble metaconglomerate and a thick metamorphosed orthoquartzite.The formation was metamorphosed to the hornblende hornfels facies by the 1,500 Ma old Wolf River Batholith.The McCaslin Formation forms a major syncline plunging 30 to the S. 20 W.The southern branch of the McCaslin range consists of overturned quartzite.The McCaslin Formation appears to have been deposited as part of a braided alluvial system.The sedimentation was influenced by the lack of land vegetation, intense weathering, and probably aeolian conditions in the source areas.Paleocurrent data show that the direction of sediment transport was mostly from west to east with substantial local variation.Clast lithologies and heavy minerals indicate mUltiple sediment sourceS.The tectonic environ ment was generally stable with slight but steady subsidence.The McCaslin Formation may correlate with several other quartzites in the region, including the Baraboo, Waterloo, Barron, Flambeau, and Sioux Quartz ites.Radiometric ages on related igneous rocks indicate deposition of these formations during the Early Proterozoic between approximately 1,760 and 1,630 Ma.Minor radioactivity of the McCaslin Formation is due to placered zircon grains.The metaconglomerate is probably too young to contain Elliot Lake type placered uranium.However, since the McCaslin-Waupee contact is not exposed and has not been studied, an unconformity-type uranium deposit can not be ruled out.,\" \ ','I Vvl"",.'/1/',1 A "", \(

The l V adsworth Till Member of the Hedron Forma tion is the youngest till unit in Illinois and was deposited during the las t advance of the Lake Nichigan Lobe to reach the southern part of the lake basin.The equivalent unit in Hisconsin is called the Oak Creek Formation (Mickelson and others, 1983) * Around the southern margin of the lake the l 1 adsworth till is found at the surface in the Valparaiso, Tinley, and Lake Border Moraines.In the sub surface it lies beneath the Lake Chica go plain and beneath nontill sediments under Lake Michigan.The composition and texture of the gray, clayey illi tic 1,adsworth till reflects incorporation of Paleozoic rock and lacustrine sedi ment from the Lake Michigan basin.Variation in composition is present in vertlcal profile and in lateral distri bution.'\.]hereas some variation is clearly associated with separate depo sitional events (Valparaiso and Lake Border), other variation appears to reflect differences in length of flow path in the l.ake Michigan basin.On the basis of the available data in the study area, the \,adsworth till is a clearly distinguishable stratigraphic unit that can be subdivided further on textural and compositional characteris tics related to geographic and strati graphic positions * T-") dvoid unnecessary use of names and to reduce confusion, Wadsworth till is (lsed in this paper to include the same unit in l V isconsin (Oak Creek Formation) Elless reference is made specifically to the Wisconsin unit 0

Study of the highly aluminous pelitic schists interbedded with the Waterloo Quartzite of southern Wisconsin suggests at least two periods of deformation followed by two separate metamorphic events (M 1 and M Z )' Both metamorphisms occurred in a static environment and althougn both probably took place under amphibolite facies conditions, M l probably represents some what higher temperature conditions than M Z ' Arguments are presented which suggest that M l occurred at P H 0 < 3. 8kb and T between 350C and 550C.Z M l and M Z clearly represent post-Penokean metamorphic events which may have occurred on a regional scale throughout much of southern Wisconsin.An age of near 1,630 m.y.seems most reasonable for these metamorphic events.