Correlation of the Three Tills of Logan County, Ohio

The author identified three Late Wisconsin tills in Logan County in 1956, related them to soils in 1965, and named them the Marysville, Bellefontaine, and Pickrelltown in 1967, but included no correlations, which have since become established and are reported here. The Marysville Till is the youngest, is clay-rich and almost pebble-free, and has a shallow soil (Morley-Blount). Next older (south) is the Bellefontaine, with a loamy, pebbly texture and also a shallow soil (old Miami 6A). Oldest and southernmost is the loamy, pebbly Pickrelltown Till, which has a deeper soil with a B3 horizon (old Miami 60). Correlation with other tills is based on field tracing of associated textures, soils, and end moraines. In western, high-lime terrain, the Marysville Till correlates with Gooding's (1963) Union City till and Goldthwait's (1965) "Hiram" Drift, later named Olentangy (Goldthwait 1989). The Bellefontaine Till correlates with Gooding's (1963) Bloomington till, later renamed the Knightstown Till by Gooding (1973) and Stewart (Goldthwait and Stewart 1981) in the Miami Lobe, and with Goldthwait's (1965,1969) Darby in the Scioto Lobe. The Pickrelltown Till correlates with Gooding's (1963) Champaign till, later renamed the Crawfordsville Till by Gooding (1973) and Stewart (1981), and with Goldthwait's (1965) older Darby Drift, which he later renamed the Caesar Till (1969). Correlation with low-lime tills in eastern Ohio was more difficult, except for the clay-rich Marysville Till, which clearly correlates with White's (1967,1982) Hiram Till. However, continuous tracing of the two loamy tills (Bellefontaine and Pickrelltown) and their related characteristics around the Scioto Lobe led to my identification (in Root et al. 1961) of two Late Wisconsin tills (unnamed) in Knox County. The two Late Wisconsin tills were associated with two phases of the low-lime Alexandria soil there, the "Centerburg" (younger) and "Mount Liberty" soils, with contrasting characteristics very similar to those of the two soils in the Bellefontaine and Pickrelltown Tills, and also to the soils in White's (1967,1982) Hayesville and Navarre Tills in northeast Ohio. (White's different correlation [1982, Table 2] is interpreted to be a simple error, because White was a competent scientist, fully aware of the unique clay-rich nature of his Hiram Till, that could only correlate not with my loamy Centerburg till but with the clay-rich tills of western Ohio, Goldthwait's "HiramVOlentangy and my Marysville.) OHIO J. SCI. 91 (1): 77-82, 1991 CORRELATION OF THE THREE TILLS OF LOGAN COUNTY, OHIO More than three decades ago, as a graduate student at Ohio State University, I mapped the glacial geology of Logan County in western Ohio, and identified three "Late Wisconsin" (Woodfordian) tills there (Forsyth 1956). Correlation of these tills with soils (as defined by soils scientists at that time) was subsequently published (Forsyth 1965), though the tills remained unnamed. These tills were later formally named in a publication on the glacial geology of the East Liberty Quadrangle in southeast Logan County (Forsyth 1967), with local names being used because of the uncertainty then about their correlation with other tills elsewhere in Ohio. Now, many years later, the correlation of these Logan County Wisconsinan tills with others, both within the state and beyond, seems fairly well established and deserves to be reported. The Three Tills of Logan County The three tills originally identified in Logan County (Forsyth 1956) and named in the quadrangle report (Forsyth 1967) are, in order of increasing age, the Marysville, Bellefontaine, and Pickrelltown Tills. These tills were distinguished from each other on the basis of their 'Manuscript received 16 May 1990 and in revised form 6 February 1991 (#90-12). geographic position, their textures in both the parent till and the B horizon of the related soil, and other soil characteristics (as reported in Forsyth 1965, though the tills were not named there). The Marysville Till occurs to the north, on and north of the Powell End Moraine, and is characterized by a clayey (clay to clay loam) texture with relatively few pebbles. It has a Morley-Blount soil (once called Miami 6B by soils scientists) developed in it, a soil with a clay texture leached to depths of about 60 cm (24 in), and lacking any clear-cut B3 horizon (Forsyth 1965). Because of the high clay content of the till, surfaces of roadside exposures commonly exhibit a poorly developed "mud-crack" pattern. The Bellefontaine Till is found farther south, from south of the Powell End Moraine to as far south as the southern boundary of the Farmersville End Moraine. Typically, this unweathered till has a loam texture and is quite pebbly. The soil developed in it is characterized by a clay texture and a somewhat sticky consistency, and also lacks a B3 horizon. This is the only one of the three tills in which the increase in clay content from the parent till to the soil B horizon is especially great, a feature interpreted by Wilding et al. (1971) to be the result of intense leaching of this very limy till, a process which removed a significant amount of bulk from the soil while concentrating the residual clay in the soil B horizon, increasing its stickiness. This would also explain the relatively shallow depth of leaching of this soil, which averages only about 62 cm (25 in), almost the 78 CORRELATION OF LOGAN COUNTY TILLS VOL. 91 same as that of the younger Marysville Till. The soil in the Bellefontaine Till was called the Miami 6A in the older soils classification (Forsyth 1965), though present soils terminology combines this soil and the deeper soil formed in the Pickrelltown Till, the old Miami 60, into the modern Miamian Soil. The Pickrelltown Till occurs to the south of both of the other tills and is not related to any end moraine in the Logan County/East Liberty area (though correlation beyond this area to the east would relate it to the Cuba Moraine). This till, like the Bellefontaine Till, has a loam texture and is quite pebbly, but the soil formed in this till (the old Miami 60 [Forsyth 1965] or Miamian of the modern soils classification) is significantly deeper (90 cm [30-40 in]), has a well-developed B3 horizon, and generally lacks the stickiness of the Miami 6A soil (Forsyth 1965). Despite all these contrasting characteristics, I would not be able to distinguish between the Bellefontaine and Pickrelltown Tills without reference to their associated soils, though the more southerly location and the distinctly deeper, more weathered soil found in the Pickrelltown Till are clear indications that this till is indeed a separate and somewhat older Woodfordian unit than the Bellefontaine Till. When work was done preparatory to publishing the East Liberty Quadrangle report (Forsyth 1967), it was also noted that the species of trees in mature woodlots appeared to differ somewhat on the three different tills, though this distinction was not striking nor definitive, especially in light of the scattered occurrence of mature woodlots in the area, so this characteristic was not used as a basis for mapping the tills, though in places it did provide a suggestion as to their identities. The woodlot contrast observed showed swamp-forest species (elm, ash, red maple) occurring characteristically on the poorly drained, heavy clays of the Marysville Till; almost pure sugar-maple stands on the Bellefontaine Till; and tuliptree, sugar maple, and beech on the Pickrelltown Till. CORRELATION WITH TILLS IN NEIGHBORING AREAS OF fflGH-IJME TILLS With all the more recent studies and mapping done in western Ohio by R. P. Goldthwait and his associates, correlation of the Logan County tills with tills in neighboring counties to the east is generally obvious, though terminology has varied somewhat. Basis for this correlation is continuous field tracing of tills, associated soils, and related end moraines, and also of overall regional patterns. The tills in west-central Ohio were first named by Goldthwait in 1965 (Goldthwait and Forsyth 1965) as the "Hiram" (a name already in use by George White for a clay-rich till in northeast Ohio [DeLong and White 1963]) for the clay-rich till on and north of the Powell Moraine and the Darby (south of the Powell Moraine). This terminology was expanded by Goldthwait and Rosengreen (1969), working in the Scioto Lobe east of Logan County, using definitions based on till textures and geographic positions, by limiting the name Darby to the till on and north of the Reesville Moraine (and south of the Powell Moraine), and introducing the name Caesar for the till south of the Reesville Moraine. Correlation of the Logan County tills with these tills named by Goldthwait and Rosengreen (1969) equates the clay-rich Marysville Till with their "Hiram" Till, the Bellefontaine Till with their Darby Till, and the Pickrelltown Till with their Caesar Till (Table 1). Goldthwait used these same names four years later in two different publications (Dreimanis and Goldthwait 1973, Goldthwait 1976), these papers adding names for two younger tills in the area lying north of Logan County: the Tymochtee Till occurring immediately north of the Hiram Till, and the Lake Till occurring still farther north (in the area of the Hoytville/St. Clair soils [Forsyth 19651). In a more recent publication (1989), Goldthwait, apparently unsure of the true correlative of White's clay-rich Hiram Till in western Ohio, used a different name, Olentangy Till, for the till he had previously called "Hiram" (equivalent to my Marysville Till in Logan County). (Goldthwait also, in the abstract for that same 1989 paper, mistakenly associates the "St. Clair" [Hoytville-St. Clair] soils with his Tymochtee Till, though those soils do not extend south of the Defiance End Moraine, their distribution being limited to the area of his Lake Till [Dreimanis and Goldthwait 1973], while it is moderately clay-rich Morley-Blount soils that occur associated with his Tymochtee Till.) Some have questioned correlations that involve, along with other methods, tracing of tills along end moraines (Totten 1969). George White, Stanley Totten, and others working with them in glaciated eastern Ohio have shown that many tills there are thin, occurring as thin veneers over pre-existing glacial features, where end-moraine topography is commonly inherited from an earlier glacial event (White 1962). Cut after cut in eastern Ohio supports this interpretation, so that using end moraines as a basis for correlation of surface tills there would indeed produce erronious results. Indeed, I made the same interpretation for the Johnstown Moraine in Knox County, based on the pattern and distribution of the tills there and the massive nature and regional implications of this moraine. In western Ohio, however, deep cuts reveal thick surface tills, while the existence of inherited end moraines thinly covered by later tills has not been demonstrated anywhere, despite the published warning about them (Totten 1969). Indeed, all exposed sections, well records, and regional patterns of tills in western Ohio uniformly support the interpretation that end moraines there were formed by the till found at their surface; thus, use of endmoraine tracing is indeed a viable tool in the regional correlation of tills there. Even so, evidence of a regional Woodfordian stratigraphy of thick till units does exist in western Ohio. The surface distribution of a younger clay-rich till (Marysville) to the north and a slightly older, more loamy, pebbly till (Bellefontaine-Pickrelltown) to the south in west-central Ohio is duplicated in a stratigraphic section exposed along the Auglaize River in northwest Ohio (Forsyth I960). There, below up to 3 m (10 ft) of alluvial and lacustrine sediments, a clay-rich till about 6 m (18 ft) thick overlies a loamy, more compact, pebbly till about 3 m (8 ft) thick lying on bedrock (Devonian Ohio Shale). The two tills are separated by a well-developed but somewhat discontinuous pavement of dolomite and crystalline boulders and cobbles, all with their upper surfaces strongly beveled and striated OHIO JOURNAL OF SCIENCE J. L. FORSYTH 79