New geophysical analysis of the Precambrian basement in Minnesota–Iowa–Wisconsin indicates that an Archean–Proterozoic boundary (Spirit Lake trend) previously recognized in NW Iowa can be continued eastward into central Wisconsin and farther east as the Spirit Lake tectonic zone (SLtz). To test the age of Paleoproterozoic crust south of this structure, several subsurface samples of Precambrian ...

19 Detrital-zircon analysis of sandstones interbedded with ca 464 Ma ignimbrites in 20 the lower Mweelrea Formation of the South Mayo Trough, western Ireland, 21 suggests Ordovician source-rock provenance that corresponds to two distinct 22 volcanic-arc phases on the Laurentian margin. East-derived sandstones contain a 23 suite of zircons with a mean age of ca 487 Ma that suggests derivation fr...

The association of free Fe oxides with soils and clays from two Enon sandy loam (Ultic Hapludalfs, fine, mixed, thermic) soil saprolite profiles was studied. Goethite was the dominant Fe oxide identified. Lepidocrocite was detected in trace amounts in some sam ples. Fe/clay ratios were highest in the epipedons of these soils suggesting the concentrating of Fe oxides as a result of alumino silic...