Floodbed sedimentology
- 出版日期：2004.
- 页数：1 v. :
- 第一责任说明：Joanne M. Livingston.
- 分类号：a211.3 ; a371
- ISBN：0612933792(ebk.) :
MARC全文
02h0029509 20120619154943.0 cr un||||||||| 120619s2004 xx ||||f|||d||||||||eng | MQ93379 0612933792(ebk.) : CNY371.35 NGL NGL NGL a211.3 ; a371 Livingston, Joanne M. Floodbed sedimentology [electronic resource] : a new method to reconstruct paleo-ice-jam flood frequency (Yukon) / Joanne M. Livingston. 2004. 1 v. : digital, PDF file. Adviser: Smith, D. G. Thesis (M.Sc.)--University of Calgary (Canada), 2004. For seven to eight months of the year the Yukon River is ice-covered in the interior of Yukon and Alaska. Between Dawson City, Yukon and Circle, Alaska, the Yukon River is narrowly-confined between steep bedrock valley walls with limited floodplain and the formation of ice jams and their related flooding is the most unpredictable hazard. In over a century of recorded river-ice break-up at Dawson City, the only floods to exceed bankfull have been ice-caused thus overbank sedimentation is the result of low-frequency - high-magnitude ice jam floods. In this thesis, I have developed a methodology to reconstruct paleo-ice jam flood histories on northern rivers for periods beyond the historic record &sim；100 years) and in the case of the Yukon River, at least 2000--3000 years. This method relies on stratigraphically logging floodbed couplets silt - organic litter) that result from ice jam floods and using radiometric and tephra chronologies for age controls. Results from radiocarbon-dated organic materials adjacent to volcanic tephra beds indicates ash deposition in the area at 1200 yr BP and 1700 yr BP respectively, for the eastern and northern lobes of the late Holocene White River ash. Long-tern frequency of ice jam floods 2000 yrs) is estimated to be once in 34 years or in every given year has a 3% probability of recurrence. Short-term &sim；500 yrs) recurrence intervals range from 12.2 to 66.6 years. Such variability implies that long-term averages may mask more frequent events occurring over shorter time periods. The average vertical sedimentation rate over 2000 years was &sim；1mm/yr suggesting that islands and floodplains in the Yukon River canyon are remarkably stable. Ice on rivers, lakes, etc. ; Floods. ; Sediments (Geology) Electronic dissertations. aeBook. aCN bNGL http://pqdt.bjzhongke.com.cn/Detail.aspx?pid=I87xPwlzhxQ%3d NGL Bs1565 rCNY371.35 ; h1 bs1204