Rocky Mountain Section–58th Annual Meeting (17–19 May 2006)
Paper No. 4-2
Presentation Time: 8:00 AM-11:40 AM

EOLIAN STRATA OF THE UPPER CRETACEOUS CAPPING SANDSTONE MEMBER, WAHWEAP FORMATION, COCKSCOMB AREA, GRAND STAIRCASE-ESCALANTE NATIONAL MONUMENT, UTAH

SIMPSON, Edward L.1, WOLF, Hannah2, SIMPSON, Wendy S.2, TINDALL, Sarah1, and JENESKY, Timothy1, (1) Department of Physical Sciences, Kutztown Univ, Kutztown, PA 19530, simpson@kutztown.edu, (2) Parkland High School, 2700 North Cedar Crest Blvd, Allentown, PA 18104

Eolian processes can be distinguished from subaqueous deposition by the presence of centimeter-scale, inversely graded wind-ripple stratification. Detailed examination of the capping sandstone member of the Wahweap Formation in the Cockscomb area in Grand Staircase and Escalante National Monument revealed the presence of eolian stratification. This eolian stratification is the first occurrence reported from the Upper Cretaceous age strata of Utah.

In measured sections, wind-ripple stratification, composed of inversely graded fine- to medium-grained sandstone, is present as (1) filling within lenticular scours that cap ephemeral fluvial bars, and (2) trough cross bed sets that record the presence of small dune fields between the braided river channels. Lenticular wind-ripple stratification sets, capping bars are at most 20 cm thick, indicating reworking by highly variable winds during prolonged exposure of the fluvial bar tops.

Stratification from small dunes occurs at two stratigraphic heights in the section north of the Gut Road. Both occurrences record the migration of the dune field across the braided stream deposits. In the uppermost occurrence of the section, the thickness of wind-ripple trough sets changes vertically from 15, 32, 25 to 20 cm, recording the encroachment of the dune field margin. Laterally, these thin trough sets are truncated by a 2 m thick set of wind-ripple strata containing cyclic wind-ripple stratification. During this time, wind was trending to the southeast. The thick trough set indicates the maximum extent of the dune field and records the migration of barchanoid dune types. Cyclic wind-ripple stratification in the main dune field may record annual fluctuations. Braided stream deposits truncate the eolian strata.

Rocky Mountain Section–58th Annual Meeting (17–19 May 2006)
General Information for this Meeting
Session No. 4--Booth# 2
Stratigraphy and Sedimentology (Posters)
Western State College: Kebler West Ballroom and Red Mountain Lounge
8:00 AM-11:40 AM, Wednesday, 17 May 2006

Geological Society of America Abstracts with Programs, Vol. 38, No.6, p. 6

© Copyright 2006 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.