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Three radiocarbon dates on wood, including one on a log from the type section of the Two Rivers till, show that the age of this till unit is unquestionably Greatlakean (post-Twocreekan).

The Two Rivers till, now formally designated the “Two Rivers Member of the Kewaunee Formation,” was named in 1973 by Evenson for fine-grained reddish-brown till found along the Lake Michigan shore north of Two Rivers, Wisconsin. The till was correlated with till of similar lithology that overlies the Two Creeks Forest Bed at the Two Creeks type section, and thus the till was considered post-Twocreekan (Greatlakean) in age. Unlike the age of the Valders till, which has been hotly debated (whether pre-Twocreekan or post-Twocreekan) during the past 15 years, the age of the Two Rivers till has not been the subject of direct controversy. However, the age of the Two Rivers till at its type locality has not previously been demonstrated by radiometrically dated material.

Part of a large log enclosed in till was collected from the Two Rivers type section in 1968, about three years before Evenson began his investigations in the Twin Rivers lowland, but the existence of this sample remained generally unknown. The wood has now been dated at 11,910 ± 120 yr B.P. (ISGS-1058), thus proving that the till is younger than the Two Creeks Forest Bed from which the log must have been derived by the ice.

Two additional dates, from a site on the south side of Kewaunee, also serve as confirming dates for the Greatlakean age of the Two Rivers till. Wood from a black, snail-rich peat layer has been dated at 11,700 ± 110 (ISGS-1061) and 11,650 ± 170 (ISGS-1234) yr B.P. The organic layer underlies fine-grained reddish-brown till that has been correlated with similar till that overlies the Two Creeks Forest Bed at its type section and thus was called Two Rivers till by Acomb and others (1982).

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