Age estimates and uplift rates for late Pleistocene marine terraces: Southern Oregon portion of the Cascadia forearc

Journal Article · Thu May 10 00:00:00 EDT 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JB095iB05p06685· OSTI ID:5073708

Muhs, D R; Whelan, J F ^[1]; Kelsey, H M; McInelly, G W ^[2]; Miller, G H ^[3]; Kennedy, G L ^[4]

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1. Geological Survey, Denver, CO (United States)
2. Western Washington Univ., Bellingham (United States)
3. Univ. of Colorado, Boulder (United States)
4. Los Angeles County Museum of Natural History, CA (United States)

Interest in the Cascadia subduction zone has increased because recent investigations have suggested that slip along plates at certain types of convergent margins is characteristically accompanied by large earthquakes. In addition, other investigations have suggested that convergent margins can be broadly classified by the magnitude of their uplift rates. The authors generated new uranium series, amino acid, and stable isotope data for southern Oregon marine terrace fossils. These data, along with terrace elevations and two alternative estimates of sea level at the time of terrace formation, allow one to determine terrace ages and uplift rates. Uranium series analysis of fossil coral yields an age of 83 {plus minus} 5 ka for the Whisky Run terrace at Coquille Point in Bandon, Oregon. A combination of amino acid and oxygen isotope data suggest ages of about 80 and 105 ka for the lowest two terraces at Cape Blanco. These ages indicate uplift rates of 0.45-1.05 and 0.81-1.49 m/kyr for Coquille Point and Cape Blanco, respectively. In order to assess the utility of the southern Oregon uplift rates for predicting the behavior of the Cascadia subduction zone, the authors compared late Quaternary uplift rates derived from terrace data from subduction zones around the world. On the basis of this comparison the southern Oregon rates of vertical deformation are not usually high or low. Furthermore, late Quaternary uplift rates show little relationship to the type of convergent margin. In the case of the southern Oregon coast, variability in uplift rate probably reflects local structures in the overriding plate, and the rate of uplift cannot be used as a simple index of the potential for great earthquakes along the southern Cascadia subduction zone.

• OSTI ID: 5073708
• Journal Information: Journal of Geophysical Research; (United States), Vol. 95:B5; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
GEOLOGIC FORMATIONS
AGE ESTIMATION
GROUND UPLIFT
OREGON
AMINO ACIDS
CONTINENTAL MARGIN
CORALS
EARTHQUAKES
FOSSILS
GEOLOGIC STRUCTURES
OXYGEN ISOTOPES
PLATE TECTONICS
PLEISTOCENE EPOCH
QUATERNARY PERIOD
SUBDUCTION ZONES
URANIUM ISOTOPES
ACTINIDE ISOTOPES
ANIMALS
CARBOXYLIC ACIDS
CENOZOIC ERA
CNIDARIA
COELENTERATA
DEVELOPED COUNTRIES
FEDERAL REGION X
GEOLOGIC AGES
INVERTEBRATES
ISOTOPES
NORTH AMERICA
ORGANIC ACIDS
ORGANIC COMPOUNDS
SEISMIC EVENTS
TECTONICS
USA
580000* - Geosciences