| Summary: | xv, 203 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. === Water and pumice accumulated behind a dam that, upon failure, scoured the c1aydominated
floodplain and deposited pumice sands across the Sycan Valley. The pumice
originated from the eruption of Mount Mazama (approximately 7660 ybp), and dam
failure occurred very shortly afterwards. In response to the flood the lower Sycan River
underwent episodes of channel aggradation and degradation. This study presents the
history of channel evolution for the lower Sycan River from 11,000 years ago to present,
based on floodplain stratigraphy and radiocarbon chronology. Seven primary periods of
channel and floodplain development are identified: I. Early Holocene Dynamic
Equilibrium; II: Sycan Outburst Flood; III. Initial Channel Formation; IV. Degradation &
Widening; V. Aggradation & Lateral Migration; VI. (Secondary) Degradation &
Widening; VII. Modern Dynamic Equilibrium. The active floodplain of the modern
lower Sycan River is flanked by terraces of the rapidly abandoned Sycan Outburst Flood
deposits. === Committee in Charge: Dr. Patricia McDowell, Chair; Dr. Jim E. O'Connor; Dr. Andrew Marcus
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