LIFE IN AN ANCIENT SEA OF SAND: TRACE FOSSIL ASSOCIATIONS AND THEIR PALEOECOLOGICAL IMPLICATIONS IN THE UPPER TRIAS SIC/LOWER JURASSIC NUGGET SANDSTONE, NORTHEASTERN UTAH by Thomas Roger Good A thesis submitted to the faculty of The University of Utah in partial fulfillment of the requirements for the degree of Master of Science in Geology Department of Geology and Geophysics The University of Utah December 2013 Copyright © Thomas Roger Good 2013 All Rights Reserved The University of Utah Graduate School STATEMENT OF THESIS APPROVAL The thesis of ______________________ Thomas Roger Good___________________ has been approved by the following supervisory committee members: ______________ Allan A. Ekdale_______________ , Chair 5 /1 4 /2 0 1 3 Date Approved _____________ Marjorie A. Chan______________ , Member 5 /9 /2 0 1 3 Date Approved ______________Randall B. Irmis______________ , Member 4 /1 6 /2 0 1 3 Date Approved and by ____________________ D. Kip Solomon_____________________, Chair of the Department of __________________Geology and Geophysics______________ and by David B. Kieda, Dean ofThe Graduate School. ABSTRACT The Nugget Sandstone is a Triassic/Jurassic eolianite in western North America. It represents a portion of one of the largest dune environments to have ever existed in the geologic record. Paleontological interest in the Nugget Sandstone has grown in recent years upon numerous discoveries of vertebrate and invertebrate body fossils, trace fossils, and plant fossils. Invertebrate trace fossils in the Nugget Sandstone near Vernal, Utah, are identified, described and highlighted in this study, with an overview of past fossil discoveries in the Nugget and Navajo sandstones. Invertebrate trace fossils in this area include Entradichnus meniscus, Entradichnus isp., Planolites beverleyensis, Taenidium isp. “A,” Taenidium isp. “B,” Skolithos and Planolites isp., ‘burrow clusters’, ‘large oblique burrows’, ‘flared burrows’, Paleohelcura, and Octopodichnus. Arthropods, such as insects and arachnids, are considered possible trace makers. Vertebrate trace fossils of this same area include Brasilichnium, Grallator, Eubrontes, Brachychirotherium, Pseudotetrasauropus, Tetrasauropus, and Otozoum. Possible sphenophytes, cycads, and algal build-ups comprise the evidence for primary production in the ecosystem. Sediment moisture must have played a key role in the production and preservation of all trace fossils in the Nugget Sandstone. Because of this, these trace fossils indicate that moisture was important for supporting such complex ecosystems, and that extended wet climatic intervals must have persisted intermittently between arid intervals. With fossil evidence for primary production, herbivorous insects, and carnivorous arachnids provided in this thesis, as well as indirect evidence for environmental moisture content during deposition of the Nugget Sandstone, a more complete picture of the paleoecology of this ancient sea of sand can be constructed. iv TABLE OF CONTENTS ABSTRACT................................................................................................................. iii ACKNOWLEDGEMENTS........................................................................................ vii Chapters 1. INTRODUCTION.................................................................................................. 1 1.1 Geologic Setting of the Nugget Sandstone............................................... 2 1.1.1 Tectoni c Setting................................................................................ 2 1.1.2 Nomenclature of the Nugget Sandstone........................................ 3 1.1.3 Age of the Nugget Sandstone......................................................... 5 1.1.4 Sedimentology and Stratigraphy of the Nugget Sandstone......... 5 1.2 Previous Work............................................................................................ 7 1.2.1 Paleontology of the Nugget and Navajo Sandstones................... 7 1.2.1.1 Trace Fossils........................................................................ 8 1.2.1.2 Animal Body Fossils............................................................ 12 1.2.1.3 Plant Body Fossils................................................................ 13 1.2.2 Paleoclimate and Paleoenvironment.............................................. 14 2. METHODS AND LOCALITIES.......................................................................... 26 2.1 Methods...................................................................................................... 26 2.1.1 Field Methods................................................................................. 26 2.1.2 Lab Methods................................................................................... 27 2.2 Locality Information................................................................................. 27 2.2.1 Site 21 - Orchid Draw................................................................... 28 2.2.2 Site 15 - Large Mounds................................................................. 28 2.2.3 Site 11 - Saints and Sinners........................................................... 29 2.2.4 Site 17 - Sounds of Silence............................................................ 30 2.2.5 Site 26 - Cub Creek Spire............................................................. 31 3. TRACE FOSSILS IN THE NUGGET SANDSTONE OF NORTHEASTERN UTAH....................................................................................................................... 37 3.1 Identification of Trace Fossils................................................................... 37 3.1.1 Entradichnus meniscus................................................................... 38 3.1.2 Entradichnus isp.............................................................................. 40 3.1.3 Planolites beverleyensis............................................................... 41 3.1.4 Taenidium isp. “A”........................................................................ 43 3.1.5 Taenidium isp. “B”........................................................................ 44 3.1.6 Skolithos and Planolites isp........................................................... 46 3.1.7 ‘Burrow Clusters’.......................................................................... 48 3.1.8 ‘Large Oblique Burrows’.............................................................. 49 3.1.9 ‘Flared Burrows’............................................................................ 51 3.1.10 Paleohelcura................................................................................. 51 3.1.11 Octopodichnus.............................................................................. 52 3.1.12 Brasilichnium.............................................................................. 54 3.1.13 Large Vertebrate Trace Fossils................................................... 54 3.2 Identity of Trace Makers.......................................................................... 56 4. PALEOECOLOGIC, PALEOCLIMATIC AND PALEOENVIRONMENTAL IMPLICATIONS OF NUGGET SANDSTONE FOSSILS................................ 88 4.1 Role of Water in the Preservation of Eolian Trace Fossils............. 89 4.1.1 Similarity of Entradichnus to Subaqueous Traces........................ 94 4.1.2 ‘Large Oblique Burrows’ Produced in Cohesive Sediment......... 95 4.2 Periods of Increased Moisture.................................................................. 96 4.3 Paleoecology of the Nugget Sandstone................................................... 100 5. SUMMARY AND CONCLUSIONS.................................................................... 107 REFERENCES........................................................................................................ 110 vi ACKNOWLEDGEMENTS This project would not have happened without the work and support of Daniel Chure and the National Park Service (NPS). Dan exudes passion and understanding of this field area and the paleontology within, and his willingness to share his time, knowledge and ideas was vital to the direction and breadth of this thesis. Allan A. Ekdale, my senior advisor and world-renowned authority on ichnology, not only acted as my scientific foundation, but he provided a philosophical and worldly perspective on topics from politics and science to fine arts and even romance, and many topics beyond during the course of my degree. His imagination, creativity and curiosity of all things is an inspiration to all those who have had the pleasure of his company. Randall Irmis and Marjorie Chan, both highly respected and influential scientists in their field, filled out my all-star committee. Their comments, edits and insights were superlative. Joshua Lively, Sherie Harding and Warren Anderson provided field assistance, petrographic analysis, and good times along the way. Some field sites and fossils discussed in this paper were discovered thanks to an NPS survey of the Nugget Sandstone during from 2009-2012 conducted in large part by Daniel Chure and George Engelmann. Other sites were located in 2011 in an additional survey of the Nugget Sandstone conducted by Joanna Panosky and Keegan Melstrom, both of whom were part of the NPS’s Geoscientists-in-the-Parks (GIP) summer program. My family has given me their full support from the start, and even traveled to Utah occasionally to also take advantage of its geologic wonders. And lastly, the newest addition to my family, Kelly Good, was an amazing field