Physical Sciences and Mathematics Commons^™

Metamorphic Evidence For Tilt Of The Spuzzum Pluton – Diminished Basis For The Baja British-Columbia Concept, E. H. Brown, Russ R. Burmester

Geology Faculty Publications

To address the question of tilt versus translation as the mechanism responsible for discordance between paleomagnetic directions of Cretaceous plutons in the British Columbia Coast Plutonic Complex and the North American reference direction, metamorphic pressures around the margin of the Spuzzum pluton have been determined. Pressures are derived from microprobe analyses and evaluation of exchange equilibria in the assemblage garnet-biotite-plagioclase-aluminum silicate-quartz. Samples studied come from eight localities in the contact aureole around the pluton and encompass the area of a previous paleomagnetic study. The analyzed samples are coarse grained and exhibit textural features indicative of equilibrium crystallization following emplacement of …

Paleomagnetism Of The Patagonian Plateau Basalts, Southern Chile And Argentina, Robert F. Butler, Francisco Herve, Francisco Munizaga, Myrl E. Beck Jr., Russ R. Burmester, Eduardo S. Oviedo

Geology Faculty Publications

A total of 505 paleomagnetic samples were collected from 65 sites (volcanic flows) of the Patagonian plateau basalts at four locations in southem Chile and Argentina. K/Ar analyses indicate that 38 flows from two locations form a Late Cretaceous group (64-79 Ma), while the remaining 27 flows are Eocene in age (42-56 Ma). Progressive demagnetization indicates that a characteristic remanent magnetization (ChRM) has been successfully isolated from 59 flows. Rock-magnetic prop­erties and analysis of ChRM directions within and between sites allow the secure inference that the ChRM is a thermoremanent magnetization acquired during original cooling. The Eocene flows yield 15 …

Sediment Budget For The Grouse Creek Basin, Humboldt County, California, Mary A. Raines

WWU Graduate School Collection

A sediment budget constructed for the Grouse Creek basin in northern California provides information on the sources and timing of sediment production to aid land managers in understanding the effects of logging impacts in a sensitive watershed. The sediment budget yields a sediment production rate of 1,750 t/km²/yr for a 29-year period. This rate is among the highest for such disturbed forested basins in the Pacific Northwest. Approximately 40 percent of the Grouse Creek basin, which is bisected by regional structural features that have created zones of weak and altered rock, has been logged in the last 35 …

Fabric Study And Structural History Of Deformed Plutonic And Metamorphic Rocks In The Holden Area, North Cascades, Washington, Gary K. Hurban

WWU Graduate School Collection

The Holden area, in the Crystalline Core of the North Cascades, contains deformed and undeformed plutons ranging from Triassic to Eocene in age.

Two deformational styles have been identified in the Holden area. Contractional deformation is indicated by steeply-plunging, down-dip, mineral and stretching lineations in the syn-tectonic Seven Fingered Jack pluton (estimated midLate Cretaceous), and in the pre-tectonic Dumbell Mountain pluton (220 Ma), associated with apparent flattened fabrics. Strike-slip shear deformation is represented by gently-plunging to subhorizontal, strike-parallel mineral and stretching lineations, which are commonly associated with constricted fabrics. These fabrics occur prominently in the Dumbell Mountain pluton, and crosscut …