David M. Mickelson, Edward B. Evenson; Pre-Twocreekan age of the type Valders till, Wisconsin. Geology ; 3 (10): 587–590. doi: https://doi.org/10.1130/0091-7613(1975)3<587:PAOTTV>2.0.CO;2
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Red tills deposited by post-Twocreekan (Valderan) ice advances of the Green Bay and Lake Michigan Lobes in eastern Wisconsin do not extend to the type locality of the Valders till. The post-Twocreekan ice of the Lake Michigan Lobe terminated at the Two Rivers Moraine, 30 km northeast of Valders. Likewise, geomorphic criteria and depth of carbonate leaching indicate that post-Twocreekan ice of the Green Bay Lobe did not reach Valders from the west.