کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
6428913 1634751 2014 11 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Very long-term incision dynamics of big rivers
ترجمه فارسی عنوان
دینامیک برش بسیار طولانی رودخانه های بزرگ
کلمات کلیدی
رودخانه طولانی پروفیل، پویایی برش، کتک زدن، غیر ارگانیک، کنزوئیک، آفریقا،
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات علوم زمین و سیاره ای (عمومی)
چکیده انگلیسی


- Regional incision markers constrain full-length African river paleoprofiles.
- Reconstructed long profiles calibrate very slow incision (5m/my) since Oligocene.
- Profiles pinned-down at divide, outlet and stationary lithogenic knickzones.
- Flexural uplift/dynamic topography mapped from profiles convexities & anomalies.

Constraining large-scale incision dynamics of shield and post-rift margin domains is key to understanding the sediment routing system over the overwhelming part of the continental surface. Based on dated and regionally correlated incision markers from West Africa, we reconstruct for the first time the entire paleo-long profiles of big rivers such as the Niger at ca. 24, 11 and 6 Ma, as well as the Eocene topography those rivers have dissected. The results provide boundary conditions and calibration for surface process models and paleodrainage dynamics. Though spatially and temporally variable, incision remained mostly below 10m/my with a mean around 5m/my. The spatial stability of both the river outlets and divides imposed maintenance or increasing concavity of the river long profiles through time, resulting from spatially contrasted adjustment of river segments bounded by recurrent lithogenic knickzones that persisted since 24 Ma. Drainages evolved preferentially by very slow slope decrease or uniform incision in between the stationary knickzones of evolving amplitude, with apparently no relation to base level change. Therefore, knickzone height or position may not simply reflect the transient response of big rivers to base level fall as predicted by stream-power incision river models. This may also challenge uplift histories of deep continental interiors retrieved from river long profiles inversion relying on such models. Very slow incision allowed amplification of the Hoggar hot spot swell and flexural uplift of the continental margin to be recorded by river long profiles, emphasizing the potential of big non-orogenic rivers as gauges of dynamic topography.

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ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Earth and Planetary Science Letters - Volume 405, 1 November 2014, Pages 74-84
نویسندگان
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