a r t i c l e i n f o There are differences in the style of collisional orogens between the Phanerozoic and the Precambrian, most notably the appearance of blueschists and ultrahigh pressure metamorphic (UHPM) rocks in the geological record since the late Neoproterozoic, whereas these rocks are absent from older orogens. Understanding collisional orogenesis in the context of present-day values ...

The internal layering and provenance of feldspar in 3 tills and in one outwash deposit at Gahanna, Ohio, were studied by determining pebble lithologies and Rb-Sr dates of feldspar. Variations in lithology of pebbles and in the Rb-Sr ratios of feldspar in the 125—250 micrometer fractions reveal discontinuities which divide the upper 2 tills into 2 subunits each. Each of the lower subunits appear...

The Upper Mississippi Embayment (UME), where the seismically active New Madrid Seismic Zone resides, experienced two phases of subsidence commencing in the Late Precambrian and Cretaceous, respectively. To provide new constraints on models proposed for the mechanisms responsible for the subsidence, we computed and stacked P-to-S receiver functions recorded by 49 USArray and other seismic statio...

55Swain, F. M., A Blumentals, and N. Prokopovich, "Bituminous and other organic substances in Pre-Cambrian of Minnesota," Am. Assoc. Petrol. Geol. Bull., 42, 173-189 (1958). M Timofeev, B. V., "Spores and phytoplankton from Proterozoic and early Paleozoic of Eurasia," in Proc. 21st Int. Geol. Congr., Copenhagen, Rept. Soviet Geologists, Problem 9, 177-188 (1960) (in Russian; English abstract, p...