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The Erie, Saginaw and Michigan ice at St. Joseph County — Montgomery's survey, restated by the modern framework
Montgomery's map: The topography chapter of the 1907 county history rests, by its own bibliography, on the geological papers of Dr. Hugh T. Montgomery of South Bend, and its account of the last ice is his. As the ice sheet entered the great lake basins, Montgomery writes, its lower margin became lobated, and three lobes converged on this county. The Maumee or Erie lobe, advancing southwest from the Lake Erie basin, carried its border into Indiana at the northeast corner of Elkhart County and west "through the northerly part of Elkhart and St. Joseph counties to a point about five miles west of South Bend," whence it angled south along the county's western border to the Wabash at Logansport: "The withdrawal of the ice-sheet from this line and the depositing of its earthy and stony contents mark the age of the lofty range of hills lying south of Mishawaka and South Bend." That border line is this ground's own glacial fact: the Erie lobe's farthest advance ran west across the northerly part of this county — across Harris Township's northern tier, across the state-line sections above Harris Prairie — before it turned south. The Lake Michigan lobe filled its basin and pushed east thirty to forty miles beyond the present shore, overlapping the northwest corner of the county and approaching near the city limits of South Bend. The Saginaw lobe, wedged between the other two, "reached a point one mile northeast of South Bend, its moraine commencing about one mile east of Notre Dame and a little south, forming the range of hills" that runs northeast past Dowagiac, Decatur and Lawton toward Saginaw Bay — a range whose first miles cross this county's northeastern upland, the ground between Notre Dame and the state line that this section covers. Of the junction he concludes: "the city of South Bend is located where three great ice lobes met." Granger stands at the junction's northeastern doorstep, on the one stretch of the county's ground that the Erie border itself crossed.
The period scale: Montgomery's ice is of its period's dimensions — a continental sheet whose source regions stood elevated two to three thousand feet, the ice itself "from five to ten thousand feet" thick — and those figures are printed here as the 1907 survey's own, not as modern measurement. His mechanism for the surface that followed — crustal depression under the ice's weight, the episode he names with his period the Champlain epoch, slow and interrupted recession laying down moraine ridges, and floods draining south by four great channels, "the Ohio, the Wabash, the Kankakee and the Desplaines," any of them "larger than the Mississippi of today" — is likewise carried as his account; what the modern literature keeps from it is the geography: three lobes, their borders, and the meltwater's southward escape.
The modern restatement: The Indiana Geological and Water Survey's updated stratigraphic framework for the Saginaw Lobe's deposits (Antinao and others, Indiana Journal of Earth Sciences, 2024) confirms the convergence in modern terms: in north-central Indiana three lobes met — the Lake Michigan Lobe from the northwest, the Saginaw Lobe from the north, the Huron-Erie Lobe from the east — and northern Indiana lies under Quaternary sediment up to several hundred feet thick. The same work names the Saginaw Lobe's late Wisconsin deposits in this region the Elkhart Formation, with three members in order — Baugo Creek, Newbury and Lagrange — and dates them by optically stimulated luminescence on the deposits' own quartz: a minimum age for the Baugo Creek Member at about 25.8 thousand years, maximum ages for the Newbury at about 25.3 thousand and pooled maxima for the Lagrange at about 25.3 thousand, from which the authors conclude that "ice margin retreat was relatively fast overall"; wood from the Lagrange Member returned radiocarbon results beyond the method's reach, greater than 46,600 and greater than 48,000 years. The Baugo Creek Member — diamicton and glaciolacustrine sediment at or around the headwaters of Baugo Creek, in southern Elkhart County, the creek that runs west through Osceola into the St. Joseph at Mishawaka's edge — is mapped over about 270 square miles across parts of six counties including this one, at observed thicknesses of 55 to 90 feet; the boundary is printed as the paper prints it: the paper does not parcel the member township by township, and this section does not parcel it further. The same framework, following Bleuer and Melhorn (1989), re-reads what Leverett's mapping called the Maxinkuckee Moraine southwest of South Bend as "a collapsed moraine-and-fan topography, derived from the northwest" — the Lake Michigan Lobe spreading fans, among them the Mishawaka Fan, whose glaciolacustrine cap (an informal facies of the Lemont Formation) the survey's laboratory has dated at 25.8 ± 5.7, 23.8 ± 3.8 and 21.7 ± 4.4 thousand years, the last, in the authors' words, "indicating the end of landscape instability." The 2024 framework proposes the name Maxinkuckee Moraine be abandoned.
Sources: Howard (1907), Chapter I, §§VI–VII — Montgomery's lobe borders, including the Erie border "through the northerly part of Elkhart and St. Joseph counties," the Saginaw moraine's commencement and range, the three-lobe junction, the Champlain epoch and the four flood channels, with the chapter's bibliography naming Montgomery's, Gorby's, Blatchley's and Thompson's geological papers as its authorities; Antinao, Fleming, Rupp, Brown, Karaffa, Loope & Jacobs, "Updated stratigraphic framework for Late Pleistocene glacial deposits of the Saginaw Lobe… Indiana," Indiana Journal of Earth Sciences 6 (2024), doi 10.14434/ijes.v6i1.38165 — the three-lobe convergence, the Elkhart Formation and its members and ages, the Baugo Creek Member's naming, distribution and thickness, the Maxinkuckee re-reading after Bleuer & Melhorn (1989), and the Lemont-capped Mishawaka Fan dates.