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Schoonmaker Reef, also known as Wauwatosa ReefSchoonmaker QuarryRaphu Station, Francey Reef, Fuller Quarry, Francey Quarry or Wauwatosa Reef, is a 425 million year-old fossilized reef in Wauwatosa

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Summary[]

Schoonmaker Reef is nationally significant in the history of geology in the United States for its crucial role in the earliest recognition of fossil reefs in North America, a major geological advancement, and for its association with the careers of some eminent nineteenth and early twentieth century geologists, including James Hall, T. C. Chamberlin, A. W. Grabau, and R. R. Shrock. These geologists used data collected from the reef to formulate theories fundamental in the study of geology.

Large fossil collections were amassed at this locality by such prominent nineteenth-century amateur naturalists as Fisk Holbrook Day and Thomas A. Greene, and fossils from this site can be found in most major and many minor museums throughout the country, including the Museum of Comparative Zoology at Harvard University, the National Museum of Natural History at the Smithsonian Institution, the American Museum of Natural History, the Field Museum of Natural History, the University of Iowa, the University of Illinois, the University of Cincinnati, the University of Michigan, the Milwaukee Public Museum, the Thomas A. Greene Geological Museum, the University of Wisconsin, the Los Angeles County Museum, San Diego Museum of Natural History, and the University of California-Berkeley.

Increase A. Lapham, Wisconsin's first scientist, was the first to collect fossils and describe the geology of the rock outcrops here in 1844. It was James Hall, however, who, in 1862, first recognized and interpreted this as a fossil reef, making Schoonmaker Reef the first ancient reef described in North America and among the first described anywhere in the world.

Thomas C. Chamberlin used the Schoonmaker Reef extensively in devising his paleoecological (study of the relationship between ancient organisms and their environment) and sedimentological (the study of sedimentary rocks and the processes by which they are formed) model of reef development, which he published in his definitive 1877 work The Geology of Eastern Wisconsin. Amadeus W. Grabau highlighted the Schoonmaker Reef in the first compendium of fossil reefs worldwide, which he published in 1903. In 1939, Robert R. Shrock published Wisconsin Silurian Bioherms, a seminal paper which relied heavily on information derived from the Schoonmaker Reef. As a result of its prominence in these classic and important works, the Schoonmaker Reef was used as the text-book example of a fossil reef throughout the first half of the twentieth century, and Wisconsin gained world renown for its ancient reefs.

Because of its notoriety, Schoonmaker Reef was visited by many university classes and professional geological field trips. On one of these (1937 Tri-State Geological Field Trip) Schoonmaker Reef became the birthplace of the National Association of Geology Teachers, the premier organization of geology teachers in the world. This site still provides good exposures of the sedimentology and paleontology of the first-described fossil reef in North America and, therefore, it will continue to be important for geological research and studies in the history of science. The period of significance for Schoonmaker Reef was chosen to begin with Lapham's unpublished description of the exposure in 1844 and to end with the publication of Robert Shrock's reef study in 1939.

Etymology[]

History[]

The Schoonmaker Reef possesses national significance in the history of science because it played a key role in the recognition and interpretation of ancient reefs in North America. It is one of two reefs in Milwaukee County considered national significant. The first, Soldier's Home Reef, was designated a National Historic Landmark in 1993.

Although Schoonmaker and Soldiers Home reefs have some features in common, they differ in many respects pertaining to their role in the history of geology. The Soldiers Home Reef is important primarily because its physical form preserves the natural topographical features of a rock hill that the early geologists observed and used to identify ancient reefs. In contrast, the Schoonmaker Reef was not important as a rock hill, but rather because it produced the largest number of fossils from a single ancient reef in the nineteenth century. It was possible to collect these fossils only because this reef had been quarried; evidence of this early quarrying still exists. These fossil collections from the Schoonmaker Reef, which can be found in museums and universities throughout the U.S., were essential in developing the ancient reef concept and identifying these features as ancient reefs.

Geologists around the world were long puzzled by unusual imbedded rock masses, or mounds, that interrupted normally flat-lying limestone strata. The solution to this enigma was finally provided by the eminent geologist James Hall, who, in 1862, was the first to accurately interpret such features in North America as ancient reefs. The Schoonmaker Reef was at the center of Hall's ground-breaking new interpretation, which represented an important advancement in geological knowledge. The Schoonmaker Reef continued to serve as the fundamental model for ancient reef development well into the twentieth century. As such, Schoonmaker Reef was the prime example of ancient reefs in geological research, and it has been featured in numerous geology text books and scholarly works.

The prominent rock-controlled hill formed by this ancient reef was quickly recognized as a valuable source of lime by early settlers in the area. Joseph Higgins is known to have burned lime at the Schoonmaker Reef in 1838; however, lime burning may have begun here as early as 1833. Silas Brown operated the lime kilns in the 1840s, and from 1850-1857, Daniel McCormick, Mason S. Daniels, Laura Hale, James Cannon, Zebulon Hall, William Watkins and Anthony Green ran the lime operation at various times. In 1857, John Schoonmaker and Isaac Van Shaick purchased the property. Van Shaick, who later sold his interest in the quarry, was active in politics, elected first as a Milwaukee alderman, then to the state legislature, and twice to the U. S. Congress.

This site is named for John Schoonmaker and his family because they operated the quarry here the longest (more than 50 years) and were its owners during the period that much of the early geological research took place. During the latter half of the nineteenth century the site was a major source of lime in the Midwest, serving the Milwaukee and Chicago markets primarily. By 1909, the lime business had ended, and George Francey of G. D. Francey Coal, Stone & Supply Company bought the site primarily to produce crushed stone for aggregate. George's nephew, Tom Francey, installed an innovative plant for crushing stone and producing concrete in 1930, which was featured in many trade journals at the time. Following Tom's death in the late 1930s, the quarry was leased by Sidney Fuller. In 1948, the Bliffert Concrete Company purchased the quarry and concrete plant from the Francey Company, but the quarry would continue to be operated through lease by the Fuller Company.

Abandoned in 1950, much of the site was filled in and built over, but the eastern portion of the site, containing both natural exposures and some of the earliest-quarried face, still remains. Without the extensive quarrying that took place at this site, the important geological relationships between reef and nonreef strata would never have been exposed, it is unlikely that Hall would have made his reef interpretation, and the large, important fossil collections could not have been assembled. Increase Alien Lapham, Wisconsin's first scientist, conducted the earliest geological study of the site and collected the first fossils from Schoonmaker Reef in 1844. 1 Around this time, Lapham sent fossils from here and other Milwaukee area localities to the prominent geologist James Hall of New York. Hall had established a North American Paleozoic reference section based on rock exposures in New York, and had been one of the first geologists to make detailed correlations between the Paleozoic rocks of eastern North America and Europe. Now, Lapham's Wisconsin fossils helped to interest him in determining how far west he could recognize his reference section. For this reason, Hall made several visits to the Milwaukee area in the 1850s to examine Lapham's fossil collections and localities, including the Schoonmaker Reef. Based on this study, in 1862, Hall became the first to recognize that the Schoonmaker Reef was a fossil "coral" reef, making it the first ancient reef recognized in all of North America. As part of his Report on the Geological Survey of the State of Wisconsin, Hall, who was then Wisconsin State Geologist, stated:

At Wauwatosa, near Milwaukee, and at other points, there are isolated hills or ridges of Coralline limestone; while the surrounding low flat ground in underlaid by the thin and heavy-bedded Waukesha limestone. At one point in this low ground there is an open quarry, and at a little distance and on the opposite side of the road there is a similar quarry, both exhibiting the thinbedded and the thickbedded portions of the rock. In direct continuation we have the face of a hill of Coralline or Geodiferous limestone [Schoonmaker], which has been quarried along an extent of several rods. This has been burned into lime, while the other beds are unfit for that purpose...

The entire mass appears like a coral reef, where the broken corals and shells are packed in a calcareous sand, the whole consolidated as a compact and nearly homogeneous mass; while as we recede from it, the more finely comminuted materials are spread over the adjacent sea-bottom, and, mingling with a little argillaceous matter, they form the thinbedded argillaceous dolomite of this region. This, at least in the present state of facts, seems to be the only satisfactory explanation which can be offered. That these isolated hills are not outliers of a former continuous mass, would seem to be proved by the sloping strata upon their flanks; and there is no reason to suppose that they have been abruptly elevated in this quiet and undisturbed region; they seem to have been small coral reefs or islands, and are known to exist only over a limited portion of the area occupied by this limestone formation.

James Hall, perhaps the most eminent geologist and paleontologist in North America during the mid to late nineteenth century, was a man of many scientific accomplishments, among which his correct interpretation of ancient reefs was the most important. Hall was born in Hingham, Massachusetts, on September 12, 1811, and was introduced to the study of natural history at an early age by his local schoolteacher. Following his public school education, Hall enrolled in the newly founded Rensselaer Institute in Troy, New York, in 1830, where he was fortunate to have two of the country's earliest and most prominent geologists, Amos Eaton and Ebeneezer Emmons, as his mentors. At the age of 21, Hall became the youngest geologist at the New York Geological Survey, only four years after his graduation from Rensselaer in 1832. Within just a few years, Hall earned a reputation as one of the country's leading geologists and paleontologists. His experience and expertise were in great demand, and while conducting an exhaustive paleontological survey of New York, Hall also served as the state geologist of both Iowa and Wisconsin in the mid-1800s.

By 1866, Hall was appointed director of the New York State Museum, and, in 1893, the position of State Geologist of New York was created especially for him. Throughout much of his life, Hall was a leader in many of the most prominent scientific societies in nineteenth century America, serving as a founder of the Association of American Geologists and the American Association for the Advancement of Science, and as a charter member of the National Academy of Sciences, still the most prestigious scientific society in the nation. He was the first president of the Geological Society of America, president of the American Association for the Advancement of Science, and a three-time vice-president of the International Congress of Geologists. A prolific researcher and publisher, Hall had formulated the concepts of geosynclines and fossil reefs, and had produced 15 quarto volumes containing more than 4000 pages of text and more than 1000 paleontological plates by the time of his death on August 7, 1898. He also trained a number of assistants who would become some of the most prominent geologists and paleontologists in North America.

Although they were first recognized and correctly interpreted by Hall, the significance of the Wisconsin reefs was underscored by the work of Thomas Crowder Chamberlin. Chamberlin ensured the fame of the Schoonmaker Reef when he focussed considerable attention on it, using it as the best example of an ancient reef, in his Geology of Eastern Wisconsin, published in 1877 while he was Wisconsin State Geologist. This classic work marked the beginning of integrated Paleozoic (the era of geological time ranging from 250 million to 560 million years ago) reef studies as Chamberlin related rock type and fossils to sedimentary processes and paleoecology. In particular, he recognized that the reefs contained fossils and rock types different from surrounding contemporaneous bedded rocks and that individual reefs differed among themselves. He chose the Schoonmaker Reef as his prime example, noting that this site furnished "the best exposures, are the most fossiliferous, and have been the subject of most discussion." In this volume, Chamberlin used the Schoonmaker Reef and nearby exposures to describe the transition from reef mound to normally bedded strata, which he illustrated in an accompanying lithograph:

If we place ourselves at the extreme western exposure, known as Busack's quarry, we shall find a section showing heavy, well defined, nearly horizontal, slightly argillaceous beds, of a rather fine, uniform, compact grain, medium hardness, smooth conchoidal fracture, and bluish gray color. Interstratified with these, are layers having the lumpy nature...The layers dip eastward to about the middle of the quarry from which they rise, but not uniformly, for at this point an east and west axis occurs, having the general trend of the ridge farther east, and with which it probably has a definite connection. An east and west section in this part of the quarry would show a dip to westward and a north and south section would exhibit the layers curved gently over the axis. But as we trace the rock eastward, it changes in nature. Near the eastern extremity, the upper layer becomes slightly irregular in bedding, and rather soft, and granular in texture.

Below this is a layer from 22 to 24 inches thick, divided into sublayers, somewhat irregularly, and occasionally showing lines of deposition. To casual observation, it appears to be a compact, fine-grained, even-textured dolomite, but closer inspection shows it to contain many small cavities that are angular and sharply defined, and are the result of the removal of minute fossils, in which the rock abounds at this point. Aside from these, the rock is as previously described, with occasional seams of argillaceous material. Below this, the rock is similar to that in the western part of the quarry. In the extreme southeastern portion exposed in connection with this quarry, the rock becomes quite irregular in structure.

There ensues at this point, unfortunately, an interruption of several rods in the exposure, so that this incipient change in structure cannot be traced to its consummation.

Passing this interval, we find at the western extremity of Mr. Schoonmaker's quarry, at the surface, a cellular, even textured, regularly bedded rock similar to that last described, but of lighter color, and more distinctly granular nature. This dips southward at an angle of about 15°. As the face of the quarry curves round to the south, the whole section is composed of similar rock down to and beneath the water that occupies the bottom of the quarry at this point. But these lower layers dip less and less, until they become horizontal, and even slightly incline toward the irregular mass. If we trace these lower layers toward the ridge, their inclination increases as well as their thickness-this latter sometimes markedly until they are lost in the obscure structure of the reef, or disappear at the surface.

As we pass eastward along the face of this ridge, now well exposed by quarrying, the dip of the ill-defined layers increases gradually to 54° when the stratification can no longer be clearly distinguished. This obscurity continues for 80 paces. There are some indications of horizontal bedding in this space, and also some that the dip is to the south, and that the exposure is along the strike of the strata, but neither observation is altogether trustworthy.

East of this, blue and lighter colored bands indicate a dip of about 30° eastward. This continues for about 35 paces, the observation at the eastern extremity showing a dip of 31° in a direction E10° to 15° S, this being the dip as exposed, not necessarily the full amount of true dip. The same qualification is true of the other observations made on the dip along the face of this exposure.

Ten paces of unexposed face succeeds, followed by 90 paces uncovered, which shows an obscure dip of about 30°E of S. Again 30 paces are concealed, beyond which a face 40 yards in length succeeds, whose dip is 33° E of S. After another interruption of 60 paces, we find the last exposure of about 10 paces length, whose very obscure stratification indicates a dip to the SW. The ridge reaches a height of about 45 feet above the sole of the quarry.

Near the summit of the ridge, at its western extremity, is a slight outcrop apparently in place, and seeming to dip to the northwestward (20°, N30°W). If this be reliable, we should infer that the ridge was comparatively narrow, as the exposure lies only 17 paces back from the face of the quarry.

The trend of the ridge, as estimated from the exposures, is a little to the north of east.

The rock at Story's and Schwickhart's quarries...is closely similar to that in the western part of Busack's quarry, and the same remark may be made of the fossils, which consist mainly of Orthoceratites. But in Busack's quarry, where the strata approach the reef, the fauna is much amplified...

From all the foregoing facts, it may be regarded as fairly demonstrated that these horizontal beds were laid down simultaneously with the formation of the mounds. The cellular nature of the rock of the latter, and the uncompressed condition of fragile fossils, are fatal to any theory of upheaval, or other violent action.


Geology[]

Present and Historic Physical Appearance[]

Schoonmaker Reef is a 425 million year-old fossil reef that grew during the Silurian Period (unit of geological time dating from 435,000,000 to 405,000,000 years ago) of Earth's history at a time when much of North America was covered by shallow tropical seas. It occurs stratigraphically within the Racine Dolomite (this is the proper name for a specific Silurian rock unit in Wisconsin and Illinois). The reef contains a large variety of marine fossil organisms, for which it is famous, including trilobites (a common type of extinct arthropod), cephalopods (shelled molluscs related to the chambered Nautilus and squids), brachiopods (sedentary invertebrate animals with a bivalved shell), bryozoans (colonial invertebrates with microscopic polyps, sometimes called moss animals), clams, snails and corals. The reef rock is composed of dolomite, a limestone-like sedimentary rock containing magnesium and calcium carbonate. Unlike most sedimentary rocks, which are found in horizontal layers, most of the reef rock is massive, mound-like, and forms a large erosion-resistant rock hill.

This reef-controlled hill occurs in the north bluff of the Menomonee River valley in Wauwatosa. The bluff here is 70 feet high, with the reef exposed in the lower 20 feet. The upper bluff, which is composed of glacial sediments and soil deposited within the last million years, is in its natural state, is heavily wooded, and has never been developed. The reef is exposed in an almost continuous 600-foot-long outcrop, most of which is a quarry face that has remained undisturbed since the time of the late nineteenth century geologic studies.

In the early 1920s, Charles B. Whimall, a national figure in urban park development who is considered the father of the renowned Milwaukee County park system, proposed that this site be included in a parkway which was to extend along the north bluff of the Menomonee River valley. The County Park Commission formally included this property in its parkway plans in 1924, but it never became part of the actual parkway. The Schoonmaker Reef can be accessed by foot, but only with the landowner's permission.

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