Jacobsville Sandstone is a red sandstone formation, marked with lightly-colored streaks and spots, primarily found in northern Upper Michigan, portions of Ontario, and under much of Lake Superior. Desired for its great durability and aesthetics, the sandstone was used as an architectural building stone in both Canada and the United States. The stone was extracted by thirty-two quarries throughout the Upper Peninsula of Michigan State. Approximately between 1870 and 1915.
The sandstone has been variously called redstone, brownstone, Lake Superior Sandstone, and Eastern Sandstone. In 1907, the Jacobsville Formation was given its current classification and the name Jacobsville, in honor of Jacobsville, Michigan, a town known for its production of the sandstone. The sandstone was deposited within terrestrial fluvial environments early in the Neoproterozoic Era.
Geology
Classification The earliest geologic studies of southern Lake Superior were made in the early 1800s. Many studies used the term Lake Superior Sandstone to describe a number of different geologic formations. Differentiation of the sandstone largely centered on an east-west division across the Keweenaw Peninsula or between the lower red and upper grey sandstones. The current definition for the Jacobsville Formation was made in 1907 by A. C. Lane and A. E. Seaman, in which the various Lake Superior sandstones were divided into the Jacobsville, Freda, and Munising. The Jacobsville reflects the sandstones described as either lower red or Eastern. They also introduced the name Jacobsville in honor of Jacobsville, Michigan, a town notable for its production of the sandstone including the "famous Portage Redstone".
Similarities in lithology and heavy mineral suites between the Jacobsville Sandstone and the Bayfield group, a similar sandstone located in northern Wisconsin, suggest they may be correlated. Jacobsville Sandstone is most similar to the group's uppermost formation, the Chequamegon Sandstone. Despite their similarities, it is unknown as to whether the two formations are one and the same. A correlation between the Jacobsville and the Freda Sandstone (instead of the Bayfield) has been suggested on the basis on similar mineralogy, texture, and stratigraphic position. The formation is similar to the Middle Run Formation in southwestern Ohio. Early studies also suggested a correlation between the Jacobsville and the Potsdam Sandstone in New York.
A red clastic layer in Putnam County, Ohio, was tentatively termed Jacobsville Sandstone in 1948 by Charles Fettke.
Description Jacobsville Sandstone is generally red, due to small quantities of iron oxides, mottled with various pinks, whites and browns. The sandstone exhibits many white streaks and spherical spots, caused by leaching and bleaching, which form sharp boundaries with surrounding colors. Its lithology varies from quartz-rich to feldspar-rich sandstone and shale. The formation consists of four distinct facies: conglomerate, lenticular sandstone, massive sandstone, and red siltstone.
The sandstone is well-cemented and contains no glacial deposits and no fossils. The grains of Jacobsville Sandstone range from in size. Based on an average from samples taken in Marquette and Alger counties, Jacobsville Sandstone is composed of: 27.4% nonundulatory quartz, 27.0% undulatory quartz, 23.0% potassium feldspar, and 12.3% silicic volcanic clasts. Smaller constituents are 3.8% polycrystalline quartz, 2.4% metamorphic, 1.4% sedimentary, 1.3% opaque, 0.8% mafic volcanic, and 0.1% plagioclase. Jacobsville Sandstone's heavy mineral suite is 84% ilmenite, 4–5% leucoxene, 4% garnet, 3% apatite, 3% zircon, and 1% tourmaline.
Extent and stratigraphy
The formation lies southeast of the Keweenaw Fault in the Keweenaw Peninsula, and south of Lake Superior further east in the Upper Peninsula. In Ontario, Jacobsville Sandstone underlies Sault Ste. Marie and extends discontinuously along the lake shore from Bar River in the south to near Wawa in the north. The formation also has a small extent in Iron County, Wisconsin. Due to the highly irregular surface on which it was deposited, the formation varies in thickness from to over in Michigan. The sandstone also underlies most of Lake Superior, west of Munising in particular, at a maximum thickness of over . The Jacobsville Formation lies unconformably beneath the Munising Formation and above the Oronto Group. The formation is an upper member of the Keweenawan Supergroup. Jacobsville Sandstone varies from horizontal to gently inclined and paleocurrents point toward the Lake Superior basin.
The Jacobsville Formation outcrops significantly throughout the Upper Peninsula, with lesser exposures in Ontario and Wisconsin. Cliffs of the sandstone tend to have blocky talus that supports little vegetation. Jacobsville Sandstone, rising only a few feet above lake level, is the oldest formation exposed in Pictured Rocks National Lakeshore. The sandstone features prominently on Grand Island in Hiawatha National Forest.
Formation and age Jacobsville Sandstone was deposited within fluvial, lacustrine, and deltaic environments. Sand and gravel were transported in streams that flowed northward out of the Northern Michigan Highlands, remnants of mountains formed during the Penokean orogeny. The streams leveled out along what is now the southern shore of Lake Superior, depositing sediment that formed the Jacobsville Sandstone. The environment of deposition was moist and humid, resulting in the sandstone's red color due to the precipitation of pigmentary hematite. Subsequent fluid flow created the bands of color in the Jacobsville where the pigmentary hematite was bleached away.
The Jacobsville Formation was deposited atop rocks of the late Mesoproterozoic Midcontinent Rift. For example, along the Sturgeon River in the Ottawa National Forest, the Jacobsville Sandstone unconformably overlies ca. 1108 million year old Midcontinent Rift basalt on which a soil had developed prior to Jacobsville Sandstone deposition. The Jacobsville is unconformably overlain by the Cambrian Munising Formation. The precise age of the Jacobsville Sandstone between these bounding constraints has long been uncertain. Precise dating of detrital zircon grains within the Jacobsville Sandstone now constrain it to have been deposited after 992.51 ± 0.64 Ma. An additional constraint on the age comes from the Jacobsville Sandstone being folded within the Keweenaw Fault zone. Motion on the Keweenaw Fault is associated with the later stages of the 1090 to 980 million year old Grenvillian orogeny. As a result, the Jacobsville Sandstone is constrained to have been deposited during the final Rigolet Phase of the Grenvillian Orogeny (1010–980 million years ago).
Aquifer The formation is a mostly unconfined aquifer, called the Jacobsville aquifer, that covers an area of . Despite being a sandstone aquifer, it has a low permeability and water largely moves through cracks and fissures which extend to a depth of about . In 1985, of freshwater were withdrawn per day for human use. A number of bedrock wells in the Jacobsville aquifer have elevated levels of uranium. The elevated uranium also contributes to high radon levels, particularly in the Keweenaw Peninsula.
Extraction
The earliest extraction of the sandstone occurred in Alger County in the 1860s with two companies providing stone to build nearby blast furnaces for the iron industry. The first widespread and commercial quarrying of the sandstone began around 1870. The industry peaked in the early 1890s. About thirty-two quarries existed over the years, clustered near Jacobsville and Marquette with others scattered along the Lake Superior coast. The end of the industry occurred variably by location, though finishing around 1915 at the outbreak of World War I.
One of the principal figures in the Jacobsville Sandstone industry was John Henry Jacobs, to whom the largest producers in the Jacobsville area were associated. The town was founded in 1884 when Jacobs opened his first quarries in the area. Both the sandstone and the town of Jacobsville are named for him.
The two main varieties of Jacobsville Sandstone that were quarried were redstone and brownstone. Redstone came from the Jacobsville area, in both uniform and variegated varieties. A purplish-brown variety of brownstone known as rain-drop, so named for its wet appearance, was described as the "most handsome stone quarried on Lake Superior." Brownstone and rain-drop were supplied from Marquette, however, supplies were generally limited. Until the early 1900s, Jacobsville Sandstone was popularly known as Lake Superior Sandstone, brownstone or redstone and prefixed by the location in which it was quarried, such as Marquette and Portage Entry (e.g., Marquette brownstone).
Technique
The sandstone was quarried as dimension stone, ton stone, and rubble stone, with dimension stone the most marketable and costly. Blocks of dimension stone typically measured . The byproduct of removing the dimension stone was rubble stone, which was either sold cheaply or discarded entirely. The sandstone was extracted between April and November, as winter could be detrimental to the stone.
When a new quarry was opened, up to of glacial drift and shale overburden was blasted and removed to access the sandstone beneath. If no cliffs of sandstone existed for a quarry face, long and narrow channels spaced four feet apart were cut to allow quarrying. A key was removed from between the channels, either by wedging or blasting, to create a space for blocks to move to as they were removed. Once the key was removed, holes were drilled horizontally under the block to be quarried and then cracked open with wedges. These large blocks were then broken down to size with wedges struck by sledgehammers. Once properly sized, the blocks were either transported by tramcar to docks or directly loaded onto ships. From there the sandstone was shipped to ports along the Great Lakes for distribution inland.
Decline + Sandstone production in Michigan Year Total value 1899 $178,038 1900 $132,650 1901 $174,428 1902 $188,073 1903 $121,350 1904 $74,868 1905 $123,123 1906 $65,395 1907 $53,003 1908 $39,103 1909 $36,084 1910 $31,233 1911 $12,985 1912 $16,438 1913 $19,224 1914–1916 —
The World's Columbian Exposition of 1893 in Chicago, with its White City, ushered in a change of style that preferred light-colored marbles and limestones over the dark color of Jacobsville Sandstone. The direction of architecture was dramatically altered within a decade at the expense of Jacobsville Sandstone, especially in the Lake Superior region. In 1896, the commissioner of mineral statistics for Michigan reported that:
Architects have pronounced against it in their plans and specifications ... for the reason that architecture must have a change of style and material the same as millinery and tailoring. They claimed that too much sandstone was being used, and that the sameness must be broken into by the use of stone of other kind and color ...
The industry began to decline and many quarries idled as previously mined sandstone was sufficient to meet demand. After several years of depressed demand, the industry rebounded around the turn of the century. However, Michigan's total output of sandstone peaked in 1902 at a value of $188,073 and fell to $12,985 by 1911. By 1914, fewer than three companies were producing sandstone in the state and thus no figures were recorded.