We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
Published online by Cambridge University Press: 06 July 2010
ABSTRACT
The Sand Wash Basin in northwestern Colorado is a southern sub-basin of the Washakie Basin of Wyoming. It contains several hundred meters of the middle Eocene Washakie Formation, overlying a thick sequence of the lacustrine Green River Formation. Late Bridgerian and earliest Uintan mammalian faunas have been recovered from several localities within the basin. Key biochronological indicators of the earliest Uintan age of the fauna include the earliest agriochoerids (Protoreodon), oromerycids (Oromeryx), as well as hyracodontids (Triplopus) and eomyids (Namatomys).
Abundant petrified wood, nonmarine stromatolites, gastropods, bivalves, fish, turtles, and crocodilians show that the Washakie Formation in the Sand Wash Basin was deposited in a marginal lacustrine-fluvial setting. Paleocurrents indicate sediment transport from the north, and the composition of the sandstones is mostly devitrified volcaniclastics derived from the Absaroka volcanic field of northwest Wyoming, or possibly the Challis volcanic field of Idaho. No sediments appear to be derived from the nearby Uinta uplift to the west.
The lower part of the sequence is all of reversed magnetic polarity, and the upper part is of normal polarity. Based on correlations with the revised magnetic stratigraphy of the Washakie Basin, the Sand Wash Basin sequence was deposited during Chrons C21r and C21n (47-48 Ma).
INTRODUCTION
During the latest Cretaceous through early Eocene, the Laramide Orogeny caused Rocky Mountain intermontane basins to subside and collect thick piles of terrestrial sediments (Dickinson et al., 1988).
To save this book to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.
