Holocene Sand Compositions from the Columbia River Basin: Compositional Diversity of Sediment from a Mixed-Provenance Region
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University of Montana ScholarWorks at University of Montana Graduate Student Theses, Dissertations, & Professional Papers Graduate School 2000 Holocene sand compositions from the Columbia River Basin: Compositional diversity of sediment from a mixed-provenance region Carla E. Brock The University of Montana Follow this and additional works at: https://scholarworks.umt.edu/etd Let us know how access to this document benefits ou.y Recommended Citation Brock, Carla E., "Holocene sand compositions from the Columbia River Basin: Compositional diversity of sediment from a mixed-provenance region" (2000). Graduate Student Theses, Dissertations, & Professional Papers. 7535. https://scholarworks.umt.edu/etd/7535 This Thesis is brought to you for free and open access by the Graduate School at ScholarWorks at University of Montana. 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HOLOCENE SAND COMPOSITIONS FROM THE COLUMBIA RIVER BASIN: COMPOSITIONAL DIVERSITY OF SEDIMENT FROM A MIXED-PROVENANCE REGION by Carla E. Brock B.S., Central Washington University, 1998 presented in partial fulfillment of the requirements for the degree of Master of Science The University of Montana 2000 Approved by: rperson Dean, Graduate School 6 ^ 3 0 “ Date Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: EP38336 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. UMT Dissartxtion PuMiahing UMI EP38336 Published by ProQuest LLC (2013). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code P r o Q ^ s t : ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Brock, Carla E., M.S., May 2000 Geology Holocene Sand Compositions from the Columbia River Basin: Compositional Diversity of Sediment from a Mixed-Provenance Region Advisor: Marc S. Hendrix Sand composition is influenced by a number of factors including weathering, transport, and depositional characteristics but ultimately is controlled by the composition of the source rocks. Relationships between sand composition and plate tectonic setting have been described, but actualistic models are needed to provide additional examples of the influences of sampling scale on sand compositions, particularly in basins with mixed provenances and multiple tectonic settings. One of the simplest ways to quantify these relationships is to study the composition of sand derived from known source areas. The Columbia River Basin in the northwest United States contains a diversity of geological provinces which makes it a good area to study the relationship between Holocene sand and known lithology types. Major geological terranes within the basin include granitic plutons exposed through uplift and erosion, continental margin strata, accreted terranes consisting of ancient volcanic arcs and their fore-arc and back-arc basins, flood basalts, volcanic provinces and a young, active, magmatic arc. Eighty-five samples of modem sand were collected from first and second-order drainage systems within the Columbia River Basin. These were mounted in thin section, and each was point-counted to determine the modal composition. These data were compared to modal compositions used in ternary classification models introduced by Dickinson and Suczek (1979) and modified by Dickinson (1983). Results from this study suggest the following: 1) Sand compositions of samples from first and second order systems may reflect tectonic setting, but the exceptions illustrate that care must be taken when trying to interpret tectonic setting based only on sand composition. 2) Sand samples collected in lower order stream systems commonly have compositions that are more closely related to the local source rocks than to the general tectonic setting of the area, showing that sampling scale outweighs tectonic setting as a control on sand composition. 3) Artificial homogenization of low-order sands does not approximate the composition of sands from continental-scale systems because of the lack of stabilization that results from the transport and weathering in a large system. 4) Sand compositions cannot be accurately estimated by modeling the areal coverage of source rocks within the drainage basin. II Reproduced with permission of the copyright owner. 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Table of Contents Page Abstract........................................................................................................ii Table of Contents ...................................................................................... iii List of Tables ...............................................................................................iv List of Figures ............................................................................................ v Introduction .................................................................................................1 Previous Work ............................................................................................6 Geologic Evolution of the Columbia River Basin .............................. 8 M ethods ...................................................................................................... 12 Description of Source Provinces .............................................................21 Boulder Bathoiith ........................................................................ 21 Idaho Bathoiith .............................................................................24 Kaniksu Bathoiith ........................................................................ 30 Challis Volcanics ......................................................................... 31 Snake River Plain........................................................................ 35 Columbia Basalt Plateau .............................................................39 Blue Mountains ............................................................................43 Kootenay Terrane ........................................................................ 47 North Cascades .............................................................................50 South Cascades .............................................................................54 Belt Basin......................................................................................59 Discussion ...................................................................................................64 Hypothesis lA .............................................................................................66 Hypothesis IB .............................................................................................71 Hypothesis 2 ............................................................................................... 76 Hypothesis 3 ........................................................................ 79 Hypothesis 4 ............................................................................................... 87 Conclusions ................................................................................................ 99 References...................................................................................................101 ill Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. List of Tables Page Table 1. Sample numbers, site locations and geologic regions ....................... 14 Table 2. Raw point-count data ............................................................................15 Table 3. Grain parameters ....................................................................................17 Table 4. Error Analysis chart ...................................................................... 20 Table 5. Samples collected from the Boulder Bathoiith region ...............24 Table 6. Samples collected from the Idaho Bathoiith region ....................29 Table 7. Samples collected from the Kaniksu Bathoiith region ............... 31 Table 8. Samples collected from the Challis Volcanics region ................33 Table 9. Samples collected from the Snake River Plain