Interactions between onshore bedrock-channel incision and nearshore wave-base erosion forced by eustasy and tectonics

N. P. Snyder, K. X. Whipple, G. E. Tucker, D. J. Merritts

Research output: Contribution to journalArticlepeer-review

42 Scopus citations

Abstract

We explore the response of bedrock streams to eustatic and tectonically induced fluctuations in base level. A numerical model coupling onshore fluvial erosion with offshore wave-base erosion is developed. The results of a series of simulations for simple transgressions with constant rate of sea-level change (SLR) show that response depends on the relative rates of rock uplift (U) and wave-base erosion (εm). Simple regression runs highlight the importance of nearshore bathymetry. Shoreline position during sea-level fall is set by the relative rate of base-level fall (U-SLR) and εm, and is constant horizontally when these two quantities are equal. The results of models forced by a realistic Late Quaternary sea-level curve are presented. These runs show that a stable shoreline position cannot be obtained if offshore uplift rates exceed εm. Only in the presence of a relatively stable shoreline position, fluvial profiles can begin to approximate a steady-state condition, with U balanced by fluvial erosion rate (ε∫). In the presence of a rapid offshore decrease in rock-uplift rate (U), short (~ 5 km) fluvial channels respond to significant changes in rock-uplift rate in just a few eustatic cycles. The results of the model are compared to real stream-profile data from the Mendocino triple junction region of northern California. The late Holocene sea-level stillstand response exhibited by the simulated channels is similar to the low-gradient mouths seen in the California streams.

Original languageEnglish (US)
Pages (from-to)105-127
Number of pages23
JournalBasin Research
Volume14
Issue number2
DOIs
StatePublished - Jun 1 2002
Externally publishedYes

ASJC Scopus subject areas

  • Geology

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