«by Majie Fan _ A Dissertation Submitted to the Faculty of the DEPARTMENT OF GEOSCIENCES In Partial Fulfillment of the Requirements For the Degree of ...»
GEOCHEMISTRY AND BASIN ANALYSIS OF LARAMIDE ROCKY
A Dissertation Submitted to the Faculty of the
DEPARTMENT OF GEOSCIENCES
In Partial Fulfillment of the Requirements
For the Degree of
DOCTOR OF PHILOSOPHY
In the Graduate College
THE UNIVERSITY OF ARIZONA
THE UNIVERSITY OF ARIZONA
GRADUATE COLLEGEAs members of the Dissertation Committee, we certify that we have read the dissertation prepared by Majie Fan entitled Geochemistry and basin analysis of Laramide Rocky Mountain basins and recommend that it be accepted as fulfilling the dissertation requirement for the Degree of Philosophy _______________________________________________________________________
Date: 4/29/09 Peter DeCelles _______________________________________________________________________
Date: 4/29/09 David Dettman _______________________________________________________________________
Date: 4/29/09 Jay Quade _______________________________________________________________________
Date: 4/29/09 George Gehrels _______________________________________________________________________
Date: 4/29/09 Kapp Paul Final approval and acceptance of this dissertation is contingent upon the candidate’s submission of the final copies of the dissertation to the Graduate College.
I hereby certify that I have read this dissertation prepared under my direction and recommend that it be accepted as fulfilling the dissertation requirement.
________________________________________________ Date: 4/29/09 Dissertation Director: Peter DeCelles ________________________________________________ Date: 4/29/09 Dissertation Director: David Dettman
STATEMENT BY AUTHORThis dissertation has been submitted in partial fulfillment of requirements for an advanced degree at the University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library.
Brief quotations from this dissertation are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be grated by the head of the major department or the Dean of the Graduate College when in his or her judgment the proposed use of the material is in the interests of scholarship.In all other instances, however, permission must be obtained from the author.
This dissertation would not have been possible without the help of many people. My husband, Wei, and my daughter, Shunshun, are my backbone, they encourage and support me for pursuing the research and career I like; my parents and siblings in China are proud of me and encourage me to be brave in a different country. I am deeply indebted to my advisors: Drs. Pete DeCelles and David Dettman for the research opportunities, and their patience, support, advice, encouragement and constructive criticism. Both of them have spent great amount of time in field and laboratory to teach me field geology and lab techniques. Dr. Dettman also offered me financial support throughout time. I am very grateful to Dr. Jay Quade for inspiration, discussion and help.
Dr. Quade deserves to be one of my co-advisors. I would like to thank Dr. George Gehrels for his help with detrital zircon analyses and Dr. Paul Kapp for helpful discussion.
Many people have assisted me during my time at the University of Arizona. Lynn Peyton and Amanda Reynolds have been great support and good friends. I thank Tamara Goldin and Dan Ross for their assistance with fieldwork in beautiful Wyoming. I sincerely thank Ailiang Gu, Alex Pullen, Andrew Kowler, Andrew Leier, Antoine Vernon, Chao Li, Derek Hoffman, Facundo Fuentes, Nathan English, Joel Saylor, John Volkmer, Shundong He, Soledad Velasco, Timothy Shanahan, Victor Valencia, and Xiaoyu Zhang for their friendship and help.
This research was supported by grants from the Geological Society of America, ExxonMobil, Chevron, The Galileo Circle of the U of A, SEPM-RMS Donald L. Smith, and SEPM Robert J. Weimer Fund.
LIST OF FIGURES………………………………
LIST OF TABLES……………………………
CHAPTER 1: INTRODUCTION
CHAPTER 2: LATE PALEOCENE HIGH LARAMIDE RANGES IN
NORTHEAST WYOMING: OXYGEN ISOTOPE STUDY OF ANCIENT RIVERWATER
OXYGEN ISOTOPE RESULTS
CALCULATION OF ANCIENT RIVER WATER δ18O VALUES
CONSTRAINTS, CORRECTIONS, AND APPLICATION TOPALEOALTIMETRY
SEASONAL δ18O VARIATION IN ANCIENT AND MODERN RIVERWATERS
High Canadian Rocky Mountains in Late Cretaceous………………...…..…33 High Surface Elevation of Eastern Laramide Ranges During Paleocene.......35 Lower Surface Elevation of the Western Laramide Province before Early Eocene
CHAPTER 3: WIDESPREAD BASEMENT EROSION IN LATE PALEOCENEEARLY EOCENE IN THE LARAMIDE ROCKY MOUNTAINS INFERREDFROM 87SR/86SR RATIO OF BIVALVE FOSSILS
GEOLOGICAL SETTING AND STRONTIUM SOURCE TERRANES...........74 STUDY AREA AND FIELD SAMPLING
Modern River Water and Shell
Modern River System
TABLE OF CONTENTS - continued
Ancient River System and Basement Erosion
Powder River Basin
The Cause of Positively Correlated 87Sr/86Sr ratios and δ18O values..............88 Implications
CHAPTER 4: SEDIMENTOLOGY, DETRITAL ZIRCON GEOCHRONOLOGY,
STABLE ISOTOPE GEOCHEMISTRY OF THE LOWER EOCENE STRATA INTHE WIND RIVER BASIN, CENTRAL WYOMING
Stratigraphy and Age Control
Indian Meadows Formation: Alluvial Fan Association
Wind River Formation: Braided River Association
SANDSTONE PETROGRAPHY AND PROVENANCE
Methods and description
DETRITAL ZIRCON U-Pb GEOCHRONOLOGY
Samples and Methods
STABLE ISOTOPE GEOCHEMISTRY
Evaluation of Diagenesis
Oxygen Isotopes and Paleoaltimetry
Carbon Isotopes, Paleoclimate and pCO2
IMPLICATIONS FOR TECTONICS
Rapid Late Paleocene-Early Eocene Uplift of Basement-Cored Ranges......135 Post-Early Eocene Regional Uplift
Shaded relief map of central and Canadian Rocky Mountains
Generalized stratigraphic columns of sedimentary successions
Measured and modeled δ18O values of ancient river water
Seasonal δ18O variation of representative fossil shells
Seasonal δ18O variation of three kinds of modern river to the east of Rocky Mountains
Regression for sampling station latitude and the δ18O values of river water in low-elevation stations within the USA
Estimated paleoelevation of the Canadian and Laramide Rocky Mountains..49 Figure 2.8.
Paleodrainage reconstruction of the studied area
Schematic cross-sections showing the mechanism of forming high Laramide ranges
Simplified geological map of the Laramide Rocky Mountains showing Sr source terranes.
Generalized lithostratigraphic columns of studied sedimentary successions in studied basins.
Maps of modern river watershed and Geology
Diagrams of 87Sr/86Sr ratio vs. Sr concentration of river water
Seasonal variation of the δ18O values and 87Sr/86Sr ratios of modern bivalve Unionids collected in the Tongue River
Diagrams of 87Sr/86Sr ratio vs. δ18O value
Diagram of 87Sr/86Sr ratio vs. Sr/Ca of modern and ancient rivers...............101 Figure 3.8.
Inferred drainage patterns and Precambrian basement exposure in late Cretaceous-early Paleocene, and late Paleocene-early Eocene....………………...........102 Figure 4.1.
General map of the United States, Wyoming and northwestern Wind River basin...............
Chronostratigraphic chart for the northwestern Wind River basin...............143 Figure 4.3. Measured sections
Photographs of northwestern Wind River basin outcrops
Ternary diagrams showing sandstones compositions
Photos of petrographic thin sections of sandstone
Photos of the zircon grains
U/Pb concordia diagrams
U-Pb age-probability diagrams
U/Pb concordia diagrams for a granite pebble
Field photos and images of thin sections of the early Eocene carbonate nodules
Results of the stable isotope analyses in this study
Simplified stratigraphy, carbon and oxygen isotope values, percentage of granite clasts, Achaean zircons, and feldspar through section
Oxygen isotope data of Early Eocene paleosol carbonate
Paleogeographic sketch maps of the northwestern Wind River basin.......159
Age constraints for the study intervals in each basin
Paleomagnetic data and paleolatitude
δ13C and δ18O values of bulk individual shells and sample locations..............54 Table 2.4. δ13C and δ18O values of micromilled representative shells
Element concentration, and corrected strontium isotope ratios for selected fossil shells
Sampling location, isotope ratios, element concentration data for modern rivers
Isotope data for modern and fossil shell
Lithofacies and interpretations used in this study
Modal petrographic point-counting parameters
Modal petrographic data
Table 4.4 U-Pb (zircon) geochronologic analyses by laser-ablation multicollector ICP mass spectrometer
Table 4.5 Major age populations of detrital zircons in modern river sand and the early Eocene Eediment
Table 4.6 Isotope results
The Laramide Rocky Mountains in western U.S.A is an important topographic feature in the continental interior, yet its formation and evolution are poorly constrained. This study uses the oxygen and strontium isotope geochemistry of freshwater bivalve fossils from six Laramide basins in order to reconstruct the spatial evolution of the paleotopography and Precambrian basement erosion in late Cretaceous-early Eocene. In addition it uses the sedimentology, detrital zircon U-Pb geochronology, and isotope paleoaltimetry of early Eocene sedimentary strata to constrain the tectonic setting, paleogeography and paleoclimate of the Wind River basin. Annual and seasonal variation in ancient riverwater δ18O reconstructed from shell fossils shows that the Canadian Rocky Mountains was 4.5±1.0 km high in late Cretaceous-early Paleocene, and the Laramide ranges in eastern Wyoming reached 4.5±1.3 km high, while the ranges in western Wyoming were 1-2 km high in late Paleocene. The 87Sr/86Sr ratios of riverwaters reconstructed from the same fossils show that Proterozoic metamorphic carbonates in the Belt-Purcell Supergroup were not exposed in the Canadian Rocky Mountains during Late Cretaceous-early Paleocene, but that Precambrian silicate basement rock was exposed and eroded in the Laramide ranges during late Paleocene-early Eocene. The sedimentary environment of the early Eocene Wind River basin changed from gravelly fluvial and/or stream-dominated alluvial fan to low-sinuosity fluvial systems. Tectonic uplift of the Washakie and Wind River Range in early Eocene formed the modern paleodrainage system, although the elevation of the basin floor was only ~500 m high at that time, and early Eocene paleoclimate is more humid than modern climate.