Abstract Our detailed mapping in the south Puget Sound basin has identified two tephras that are tentatively correlated to tephras from Mount St. Helens and Mount Rainier dated ca. 100-200 ka and 200 ka, respectively. This, plus the observation that fluvial and lacustrine sediments immediately underlying the Vashon Drift of latest Wisconsin age are nearly everywhere radiocarbon infinite, suggests that glacial and nonglacial sediments of more than the past five oxygen-isotope stages are exposed above sea level. Distal lacustrine advance outwash equivalent to the Lawton Clay in the Seattle area is conspicuously absent. Instead, a thick (>120 ft) glaciolacustrine silt below the Vashon sediments contains dropstones and is radiocarbon infinite. Elsewhere, coarsegrained advance Vashon outwash rests unconformably on radiocarbon-infinite non-glacial sediments. These relationships may imply that late Pleistocene tectonic activity has modified the paleotopography and stratigraphy of the south Puget Sound area.

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Full article available in PDF version.

Full article available in PDF version.

Full article available in PDF version.

Full article available in PDF version.

Full article available in PDF version.

Abstract The Upper Cretaceous strata of the Western Interior of North America contain a rich molluscan fauna and abundant intercalated bentonites. This combination has permitted the development of a detailed time scale for the Late Cretaceous. Volcanic rocks are rare in the Lower Cretaceous of North America. Several isolated time-scale points have been reported for Lower Cretaceous rocks, but the Early Cretaceous time scale is not well defined. Nearly all of the available isotopic ages are K-Ar mineral ages. Data have been recalculated using decay constants for K 40 based on the refined activity data for K 40 and the isotopic abundance of K 40 . The best current estimates for system and series boundaries are: Cretaceous-Tertiary boundary65 to 66 m.y.; Lower Cretaceous-Upper Cretaceous boundary96 m.y.; Jurassic-Cretaceous boundary138 ± 3 m.y.