Bedrock geology of the Lake Tapps Quadrangle, Pierce County, Washington.
Gard-Leonard-M Jr. (1968) Bedrock geology of the Lake Tapps Quadrangle, Pierce County, Washington. U. S. Geological Survey Professional Paper. Pages B1-B33. 1968.
| Authors | Gard-Leonard-M Jr. |
|---|---|
| Year | 1968 |
| Title | Bedrock geology of the Lake Tapps Quadrangle, Pierce County, Washington. |
| Source | U. S. Geological Survey Professional Paper. Pages B1-B33. 1968. |
| Publisher | U. S. Geological Survey. Reston, VA, United States. 1968. |
| Document type | Serial; Report |
| ISSN | 1044-9612 |
| GeoRef | 1968-050276 |
| Keywords | areal-geology; Cenozoic-; General-description; geologic-maps; igneous-rocks; intrusive-rocks; Lake-Tapps-quadrangle; maps-; petrology-; sedimentary-rocks; stratigraphy-; Tertiary-; United-States; USGS-; volcanic-rocks; Washington- |
Abstract
Bedrock in the Lake Tapps quadrangle consists of more than 11,000 feet of Eocene and Oligocene sedimentary and volcanic rocks of the Puget Group and Ohanapecosh Formations, intrusive rocks of probable Oligocene or Miocene age, and thin Miocene sedimentary deposits. The Puget Group is subdivided into the Carbonado, Northcraft, and Spiketon Formations. The Northcraft, a wedge of andesitic volcanic breccias, separates the coal-bearing arkosic Carbonado and Spiketon Formations. The Miocene deposits are probably equivalent to part of the Ellensburg Formation which lies east of the Cascade Range. During Oligocene time, Eocene and Oligocene strata were folded in a north-trending north-plunging anticline. This large anticline contains several smaller, tightly folded anticlines and synclines broken by high-angle reverse faults which parallel the fold axes.