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Date of Award
Fall 2024
Document Type
Masters Thesis
Department or Program Affiliation
Geology
Degree Name
Master of Science (MS)
Department
Geology
First Advisor
Foreman, Brady
Second Advisor
Pfeiffer, Allison
Third Advisor
Clark, Douglas H., 1961-
Abstract
Large-scale depositional rivers typically develop into either braided or meandering morphology linked, partially, to the boundary conditions within the basin. In alluvial stratigraphy, vertical sandbodies, in many cases yield lithofacies characteristics that are nonunique for endmember planform fluvial systems. Within fluvial sandbodies, sedimentary structures preserve paleo-flow directions (i.e., paleocurrents) tied to the sinuosity of the channels. The spread of these directional measurements can be quantified by calculating dispersion for the dataset. In this study I calculated dispersion values linked to the known planform morphologies of 112 modern rivers. For each channel, the centerline azimuth directions (n = 250) were consecutively measured over a defined section of the river. To replicate natural variation in bedform directions from channel centerline azimuth, a “transport anomaly” value, calculated from the difference between bedform direction and channel azimuths in modern rivers, was randomly assigned to each channel azimuth. Results show dispersion for braided systems ranged from 0.600 to 0.775 meandering systems ranged from 0.275 to 0.581, showing a clear separation between end-member morphologies. This suggests morphology can be recovered from large (n > 55) paleocurrent measurements from a fluvial sandbody. The dataset shows dispersion correlates (R2 = 0.92) with sinuosity of meandering rivers. This allows the quantitative estimate of paleo-sinuosity from outcrops. I evaluated this approach using two case studies in Cretaceous and Paleogene strata of Utah and Wyoming, respectively, wherein fluvial sandbody channels crop out as inverted topographic features. Both braided and meandering dispersion and sinuosity reconstructions were successful identifying known morphology and sinuosity.
Type
Text
Keywords
Paleocurrent, Fluvial, Morphology, Braided, Meandering, Dispersion, River, Bedform, Sinuosity, Paleo-flow
Publisher
Western Washington University
OCLC Number
1473754736
Subject – LCSH
Paleocurrents; Fluvial geomorphology; Morphology; Meandering rivers; Sedimentary structures
Format
application/pdf
Genre/Form
masters theses
Language
English
Rights
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.
Recommended Citation
Semeraro, Anthony, "Paleocurrent dispersion applied to constrain channel planform morphology of ancient river systems" (2024). WWU Graduate School Collection. 1339.
https://cedar.wwu.edu/wwuet/1339