The Manson Impact Structure: 40Ar/39Ar age and its distal impact ejecta in the Pierre Shale in southeastern South Dakota

Science
By: , and 

Links

Abstract

The 40Ar/39Ar ages of a sanidine clast from a melt-matrix breccia of the Manson, Iowa, impact structure (MIS) indicate that the MIS formed 73.8 ± 0.3 million years ago (Ma) and is not coincident with the Cretaceous-Tertiary boundary (64.43 ± 0.05 Ma). The MIS sanidine is 9 million years older than 40Ar/39Ar age spectra of MIS shock-metamorphosed microcline and melt-matrix breccia interpreted earlier to be 64 to 65 Ma. Grains of shock-metamorphosed quartz, feldspar, and zircon were found in the Crow Creek Member (upper Campanian) at a biostratigraphic level constrained by radiometric ages in the Pierre Shale of South Dakota that are consistent with the 40Ar/39Ar age of 73.8 ± 0.3 Ma for MIS reported herein.

Study Area

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title The Manson Impact Structure: 40Ar/39Ar age and its distal impact ejecta in the Pierre Shale in southeastern South Dakota
Series title Science
DOI 10.1126/science.262.5134.729
Volume 262
Issue 5134
Year Published 1993
Language English
Publisher AAAS
Contributing office(s) Eastern Geology and Paleoclimate Science Center
Description 4 p.
First page 729
Last page 732
Country United States
State South Dakota
Google Analytic Metrics Metrics page
Additional metadata about this publication, not found in other parts of the page is in this table