Pg. 4 (table 1); App., p. A2-1. Marathon Formation. Occurs in the Chippewa Sublobe in Marathon, Wood, and Clark Counties, Wisconsin, where it is typified by a water-eroded landscape having thin light-gray, yellow, or brown till, sand, and gravel deposits. Subdivided into the lower Wausau Member (new), consisting of brown loam till, and the upper Edgar Member (new), consisting of siltier brown loam till. Thickness 0 to 20 m. Unconformably overlies Precambrian bedrock. Is the surface unit in most of Marathon County. To the north and west underlies Lincoln and Copper Falls Formations (both new), and to the east underlies Horicon Formation (new); contacts are sharp. Age is Pleistocene (probably early Wisconsinan or older).
Type section: gravel pit on west side of Ryan Street, 1.5 mi (2.4 km) south of Highway 29, in SW/4 SW/4 NE/4 sec. 27, T. 28 N., R. 8 E., [approx. Lat. 44 deg. 52 min. 50 sec. N., Long. 89 deg. 32 min. 24 sec. W.], Wausau 15-min quadrangle, Marathon Co., central WI.
Named from Marathon Co.; name credited to William N. Mode.
Reference sections = type and reference sections of Edgar Member and reference section of Wausau Member.
[Additional locality information from Syverson and others, 2011, Wisconsin lexicon of Pleistocene units, Wisconsin Geol. Nat. Hist. Survey Tech. Rpt., no. 1; supplemented from USGS historical topographic map collection TopoView, accessed on June 9, 2018.]

Source: Publication; US geologic names lexicon (USGS Bull. 1565, p. 191).

Pg. vi (chart), 4-7. Marathon Formation. Revised to include Medford Member (new), a silty till, 4 to 7 m-thick (in subsurface), below Edgar Member and above Wausau Member (both of Marathon Formation). Age is tentatively considered pre-Wisconsinan.

Source: Publication.