Abstract/Details

Paleoenvironmental reconstruction of an active margin coast from the Pleistocene to the present: Examples from southwestern Oregon


2005 2005

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Abstract (summary)

This study illustrates geoarchaeological and paleoenvironmental approaches to the investigation of an active margin coastal setting and provides examples of how information gleaned through examination of the stratigraphic record can reveal depositional signatures that provide insights into the geomorphic and tectonic forces active within coastal river basins. Three case studies from the southern Oregon coast illustrate the complex relationship between tectonics and geomorphic processes along an active margin coast such as Oregon's Cascadia subduction zone. This work illustrates that the differential preservation of late Pleistocene-age terrestrial deposits in Oregon's coastal landscape, and the early cultural sites they may contain, is not random but can be closely related to larger tectonogeomorphic processes operating at local and regional scales.

Detailed subsurface investigation of one case study site, the lower Sixes River valley, reveals a complex history of depositional environment evolution in relation to geomorphic and tectonic forces. Litho- and biostratigraphic data sets are used to develop a depositional environment reconstruction for the lower Sixes River site through time. This reconstruction of the depositional environment from the late Pleistocene to the present indicates a transgressive evolution that differs from models of transgressive coastal facies and from other studied Northwest coast estuarine life histories. Factors such as eustatic sea level rise, regional and local tectonic alteration of the landscape, sediment supply, or valley morphology may have played roles in the creation and preservation of this atypical depositional sequence.

Litho- and biostratigraphic evidence of six Cascadia subduction zone earthquakes younger than 6200 cal yr BP is recorded in a long sediment core from the Sixes River valley. All six of these events correlate with events previously reported for the area by Kelsey et al. (2002). At least five additional plate boundary earthquakes lowered tidal marshes and freshwater wetlands prior to 6200 cal yr BP. The presence within the lower Sixes River valley of an intertidal environment capable of recording Cascadia subduction zone earthquakes dating to the late Pleistocene and early Holocene has not been found at any other location on the Northwest coast.

Indexing (details)


Subject
Geography;
Geology;
Archaeology;
Paleontology
Classification
0368: Geography
0372: Geology
0324: Archaeology
0418: Paleontology
Identifier / keyword
Social sciences; Earth sciences; Active margin; Coast; Oregon; Paleoenvironmental; Pleistocene
Title
Paleoenvironmental reconstruction of an active margin coast from the Pleistocene to the present: Examples from southwestern Oregon
Author
Punke, Michele Leigh
Number of pages
171
Publication year
2005
Degree date
2005
School code
0172
Source
DAI-B 66/11, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
0542387476, 9780542387470
Advisor
Jones, Julia A.
University/institution
Oregon State University
University location
United States -- Oregon
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3194150
ProQuest document ID
305407343
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/305407343
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