Guidebook of the western United States : Part D. The Shasta route and coast line

Abstract

Principal Divisions of Geologic Time a [A glossary of geologic terms is given on pp. 133-136.] Era. Period. Epoch. Characteristic life. Duration, according to various estimates.

Polyphyly of the Pikeminnows (Teleostei: Cyprinidae) Inferred Using Mitochondrial DNA Sequences

“…These data do not allow us to state whether the pikeminnows in the Pacific Northwest have been there since the early Miocene, when the group is postulated to have migrated into North America over the Bering land bridge, or whether they reinvaded the area from Lake Idaho when the Snake River was captured by the Columbia River system during the Pliocene. However, the close association between the northern pikeminnow and Umpqua pikeminnow (Figure 3) corresponds to a hypothesized origin of the Umpqua pikeminnow from a common ancestor it shared with northern pikeminnow after a stream capture between the Willamette and Umpqua River basins (Diller 1915;Minckley et al 1986;Mayden et al 1991). Although no time estimate is given for that stream capture event, confidence intervals surrounding our divergence time estimates suggest that it probably occurred during the late Miocene or Pliocene (Figure 4).…”

Gigantic debris avalanche of Pleistocene age from ancestral Mount Shasta Volcano, California, and debris-avalanche hazard zonation

“…2, 3, 4) have puzzled geologists for many years. Diller and others (1915) noted that the hills consist of volcanic rock and stated that they "appear to be, in part at least, the products of minor and local eruptions that broke through the Cretaceous beds, each vent contributing its little pile of material." Fenner (1923) subsequently proposed that a shallow sill had been intruded beneath Shasta Valley and that small bodies of magma rose from the sill to the surface to form the individual hills.…”