عنوان
پدید آورنده
موضوع
رده
کتابخانه
محل استقرار
شماره کتابشناسی ملی
شماره
TLpq304444142
زبان اثر
زبان متن نوشتاري يا گفتاري و مانند آن
انگلیسی
عنوان و نام پديدآور
عنوان اصلي
Bedrock channel evolution:
نام عام مواد
[Thesis]
نام نخستين پديدآور
G. S. Hancock
عنوان اصلي به قلم نويسنده ديگر
Dates and simulations of fluvial terrace development and measurements of rock erosion rates
نام ساير پديدآوران
R. S. Anderson
وضعیت نشر و پخش و غیره
نام ناشر، پخش کننده و غيره
University of California, Santa Cruz
تاریخ نشرو بخش و غیره
1998
مشخصات ظاهری
نام خاص و کميت اثر
192
یادداشتهای مربوط به پایان نامه ها
جزئيات پايان نامه و نوع درجه آن
Ph.D.
کسي که مدرک را اعطا کرده
University of California, Santa Cruz
امتياز متن
1998
یادداشتهای مربوط به خلاصه یا چکیده
متن يادداشت
Fluvial strath terraces provide a record of river incision and the timing of climatic perturbations to the fluvial system. We measure Be and Al profiles to date terraces along the Wind River, Wyoming, with correction for nuclide inheritance. These terraces appear to reflect oscillation in headwater glaciation. Dates from one terrace (WR-3) are 118-125 ka, which agree with dates on moraines, and are consistent with the model of terrace-glacial relationship. Nuclide inheritance is significant in clasts. We obtain mean rates of exhumation of 13-130 m/My at the source and usd{>}{\sim}usd10 ka travel times using this inheritance. Our older terrace ages appear too young; a plausible explanation is eolian deflation. Our efforts emphasize that geologic caution, independent ages, and multiple sites are needed to date surfaces with cosmogenic radionuclides. We use a one-dimensional numerical stream simulation model incorporating sediment transport and vertical and lateral rock erosion to explore stream response to variations sediment supply, sediment size, and water discharge. Model results suggest that in order to form terrace sequences: (1) input variability must be sufficient to produce high amplitude variations in vertical erosion; and (2) rapid valley widening rates to generate sediment accommodation space. Terrace formation timing is dependent on the dominant input and lags the input cycle. The formation of terrace floors may span thousands of years. Observations on the Indus River, Pakistan, suggest that quarrying and abrasion are the primary rock erosion processes. Quarrying is the most efficient process when joints are close, but requires "preparation" to free a block. The block thickness a river can quarry increases with usd\nu\sp2.usd Rock abrasion should increase with usd{\sim}\nu\sp5,usd and is most effective in separated flow, suggesting it occurs primarily by suspended sediment. Calculations suggest cavitation is not a major process. Total abrasion measured over 1 year using drill holes is usd\leusd4 mm, and cosmogenic radionuclides from the same bed reveal average erosion rates of 0.25-0.50 mm/yr over 1.5-2.0 ka. We reconcile these measurements by appealing to the migration of bedforms. Incision rates are controlled by conditions below the resolution of reach-based erosion rules, presenting a significant modeling challenge.
موضوع (اسم عام یاعبارت اسمی عام)
موضوع مستند نشده
Bedrock channel
موضوع مستند نشده
Earth sciences
موضوع مستند نشده
Fluvial
موضوع مستند نشده
Geology
موضوع مستند نشده
Rock erosion
موضوع مستند نشده
Terrace development
نام شخص به منزله سر شناسه - (مسئولیت معنوی درجه اول )
مستند نام اشخاص تاييد نشده
G. S. Hancock
مستند نام اشخاص تاييد نشده
R. S. Anderson
دسترسی و محل الکترونیکی
نام الکترونيکي
مطالعه متن کتاب وضعیت انتشار
فرمت انتشار
p
اطلاعات رکورد کتابشناسی
نوع ماده
[Thesis]
کد کاربرگه
276903
اطلاعات دسترسی رکورد
سطح دسترسي
a
تكميل شده
Y
