U.S. Geological   Survey   Geologic Investigations Series I-2538  Online version 1.0

**Geologic   Map of the Snoqualmie Pass 30 x 60 Minute Quadrangle, Washington**

*By*

**R.W.   Tabor, V.A. Frizzell, Jr., D.B. Booth, and R.B. Waitt**

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| Looking north         from the Cascade Crest near Arch Rock. Light-colored beds in foreground         are well-bedded volcanic-clastic rocks of the Miocene Fifes Peak Formation         (unit Tfv). Dark andesitic flows of the Fifes Peak (Tf) are beyond. The         highest peak on the right skyline is Mount Stuart (9,415 ft). Ridges between         Mount Stuart and the Fifes Peak outcrops are carved from volcanic rocks         of the mostly Eocene Naches Formation.

        Fir-covered flats beyond the bedded Fifes Peak outcrop are in the vicinity         of Naches Pass. On the skyline beyond that is Mount Daniel, a Tertiary         volcanic complex, possibly correlative with the Oligocene Ohanepecosh         Formation. West of Mount Daniel, sharply pointed peaks are in the Chimney         Rock-Overcoat Peak area and are underlain by thermally metamorphosed Naches         volcanic rocks. |

 

| The Snoqualmie       Pass quadrangle lies at the north edge of a Tertiary volcanic and sedimentary       cover, where the regional structural uplift to the north elevated the older       rocks to erosional levels. Much of the quadrangle is underlain by folded       Eocene volcanic rocks and fluvial deposts of an extensional event, and these       rocks are overlain by Cascade arc volcanic rocks: mildly deformed Oligocene-Miocene       rocks and undeformed younger volcanic rocks. Melanges of Paleozoic and Mesozoic       rocks are exposed in structural highs in the northern part of the quadrangle.       The quadrangle is traversed north to south by the Straight Creek Fault,       and the probably partially coincident Darringon-Devils Mountain Fault. A       rich Quaternary stratigraphy reveals events of the Frazer glaciation. |
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Jump to USGS Data Series 186:  Database for the Geologic Map of the Snoqualmie Pass 30-Minute by 60-Minute Quadrangle, Washington (I-2538)

For questions about the content of this report, contact Rowland Tabor

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This map   and the accompanying pamphlet are also available from:

USGS Information   Services, Box 25286,   Federal Center, Denver, CO 80225  telephone: 888-ASK-USGS; e-mail: infoservices@usgs.gov

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URL of this page:   https://pubs.usgs.gov/imap/i2538/  Maintained by: Michael Diggles  Created: April 17, 2001  Last modified: May 18, 2006 (mfd)