As the Nation’s principal conservation agency, the Department of the Interior has basic responsibilities for water, fish, wildlife, mineral, land, park, and recreational resources. Indian and Territorial affairs are other major concerns of America’s “Department of Natural Resources.” The Department works to assure the wisest choice in managing all our resources so each will make its full contribution to a better United States—now and in the future.

This publication is one in a series of research studies devoted to special topics which have been explored in connection with the various areas in the National Park System. It is printed at the Government Printing Office and may be purchased from the Superintendent of Documents, Government Printing Office, Washington, D.C. 20402.

Library of Congress Cataloging in Publication Data

McGrew, Paul Orman, 1909-

The geological history of Fossil Butte National Monument and Fossil Basin.

(National Park Service occasional paper; no. 3)

Bibliography: p.

Includes index.

1. Geology—Wyoming—Fossil Butte National Monument.

2. Geology, Stratigraphic—Eocene.

3. Paleontology—Eocene.

4. Fossil Butte National Monument, Wyo.

I. Casilliano, Michael, joint author.

II. Title.

III. Series: United States. National Park Service. National Park Service occasional paper; no. 3.

QE182.F67M3 557.87'82 75-17511

Contents

INTRODUCTION 1

LOCATION 1

HISTORICAL BACKGROUND OF RESEARCH 1

STRATIGRAPHY 5

Thaynes Limestone 7

Evanston Formation 7

Wasatch Formation 7

Basal Conglomerate Member 9

Lower Member 9

Main Body 11

Sandstone Tongue 11

Mudstone Tongue 12

Bullpen Member 12

Tunp Member 12

Age of the Wasatch Formation 12

Depositional Environment 13

Green River Formation 13

Fossil Butte Member 13

Angelo Member 14

Age of the Green River Formation 14

Depositional Environment 14

Fowkes Formation 15

Sillem Member 15

Bulldog Hollow Member 15

Gooseberry Member 15

Age of the Fowkes Formation 15

Depositional Environment 15

QUATERNARY 15

THE GEOLOGIC STRUCTURE OF FOSSIL BASIN 15

PALEONTOLOGY 19

Flora 19

Invertebrates 20