MAGNETIC STRATIGRAPHY OF PLIOCENE DEPOSITS OF THE GLENNS FERRY FORMATION, IDAHO, AND ITS IMPLICATIONS FOR NORTH-AMERICAN MAMMALIAN BIOSTRATIGRAPHY

Correlation of mammalian biostratigraphy with magnetic stratigraphy is here expanded to include terrigenous Pliocene deposits of the Glenns Ferry Formation of the western Snake River Plain. Weakly magnetized fine-grained sediments as well as basaltic lava flows are used to delineate a magnetic stratigraphy for the Glenns Ferry Formation extending from the Cochiti event of the Gilbert reversed epoch to the lowermost portion of the Matuyama epoch. Curie temperature analyses and isothermal remanent magnetization studies indicate that the dominant magnetic mineral in the sediment samples is Ti-rich magnetite, probably of detrital origin.