Rowland Tabor - Geology of the North Cascades: A Mountain Mosiac

A Mountain Mosaic

ROWLAND TABOR AND RALPH HAUGERUD

Drawings by Anne Crowder

Published by The Mountaineers Books 1001 SW Klickitat Way, Suite 201 Seattle, WA 98134

1999 by The Mountaineers Books

All rights reserved

First printing 1999, second printing 2002, third printing 2006, fourth printing 2010

No part of this book may be reproduced in any form, or by any electronic, mechanical, or other means, without permission in writing from the publisher.

Distributed in the United Kingdom by Cordee, www.cordee.co.uk

Manufactured in the United States of America

Edited by Stephen R. Whitney

Drawings by Anne Crowder

Cover and book design by Ani Rucki

Layout by Ani Rucki

Cover photograph: North Cascades National Park, WA. Dike and Southern Pickets James Martin.

The publishers have generously given permission to use quotations from the following works:

The Dharma Bums by Jack Kerouac. 1958 by Jack Kerouac, copyright renewed 1986 by Stella Kerouac and Jan

Kerouac. Used by permission of Viking Penguin, a division of Penguin Putnam, Inc.

August on Sourdough from The Back Country by Gary Snyder. 1966 by Gary Snyder. Reprinted by permission of New Directions Publishing Corp.

Library of Congress Cataloging-in-Publication Data

Tabor, R.W. (Rowland W.)

Geology of the North Cascades: a mountain mosaic / Rowland Tabor and Ralph Haugerud; drawings by Anne Crowder. 1st ed.

p.cm.

Includes bibliographical references.

ISBN 0-89886-623-5

1. GeologyCascade Range. 2. GeologyWashington (State)

I. Haugerud, Ralph Albert. II. title.

QE176.C37T33 1999

557.975dc21

9852131

CIP

Printed on recycled paper

ISBN (paperback): 978-089886-623-0

ISBN (ebook): 978-1-59485-304-3

Plate 1. In the right foreground, where it descends steeply, North Klawatti Glacier breaks into a heavily crevassed icefall. Almost all the visible rock is Eldorado Orthogneiss, a 90-million-year-old stitching pluton in the Metamorphic Core Domain. Mount Buckner is on the left skyline and Mount Forbidden is hidden in the clouds.

Plate 2

Area of Geologic Map showing major faults, domains, and a few young plutons that obscure the faults.

EXPLANATION

). The gray rock to the right of American Border Peak is a small arc-root pluton. Rocks in the contact zone around it weather rusty brown.

Plate 3B. Late summer snow highlights beds of sandstone from the Methow Ocean (Harts Pass Formation). Looking south along the Cascade Crest from Mount Winthrop.

Plate 3C. Remnants of the ancient Black Buttes volcano rise up above the Deming Glacier. A younger member of the Cascade Volcanic Arc, the volcano erupted about 500,000 years ago.

).

Plate 4B. Banded gneiss in the Skagit Gneiss Complex is crosscut by a sharply bounded granite orthogneiss dike. Such dikes are the caulk of the Eocene extensional event. Head of Torrent Creek, west of Sourdough Mountain.

Plate 4C. Cascade Peak (left middle distance) is held up by contact-metamorphosed Cascade River Schist. Mixup Mountain (right) is carved from Magic Mountain Gneiss. The aligned snow patches and talus stretching from the foreground to Cache Col (right of Mixup) show the location of the Cache Col Fault, where the crushed rock erodes a little faster to make a swale (). Eldorado Peak, underlain by the Eldorado Orthogneiss, is on the skyline at far left.

Plate 5A. A blocky joint pattern and light color is typical of granitic rocks such as the tonalite and granodiorite of the Chilliwack batholith (here being traversed by geologists) on west ridge of Mount Challenger (photo by John Harbuck).

Plate 5B. Conglomerate of the Methow Ocean near Woody Pass. The cobbles of granitic rock (white with black speckles) may have come from mountains eroded in Mexico ().

Plate 5C. Fragments of greenstone, sandstone, and other rocks in disrupted argillite. Bell Pass Mlange below the Shuksan Thrust Fault, south side of Suiattle Mountain.

Plate 5D. Found Lakes were carved by glaciers from the granodiorite of a stitching pluton in the Cascade Metamorphic Core. The foreground lake has no glacial silt in the water; the far one does.

LOCATION MAP FOR POINTS OF GEOLOGIC INTEREST MAPS