Climate-cycle driving geomorphology process in the Earth
School of Earth Sciences, China University of Geosciences,, Wuhan, China
Glacial-interglacial cycles presented extreme climate on Earth, droving Earth surface changes. Geomorphological process is driven by tectonics in large time scale. While in the glacial-interglacial time-scale surface process was mainly driven by cyclic climate changes. The current abstract presents a hypothesis of cyclic-climate-change driving geomorphological process in both inclosed arid area and open fluvial area.
Since 70 ka sea level was in general decreasing. In the last glacial maximum at about 20 ka sea level was >120 m lower than present. This led to (1) strong wind erosion in arid enclosed inland areas, and (2) strong fluvial erosion in open river systems.
In deglacial starting at 17 ka earth temperature increased rapidly, and at 11 ka was close to present. This led to (1) decrease in wind erosion in arid inland, and (2) rapid accumulation in open river systems due to rapid sea-level increase. In the Holocene starting at 11 ka climate was relatively stable. Thus the most possible continuous accumulation on land was since deglacial to present.
The Earth has experienced this glacial-interglacial cyclic change for many times during the Quaternary.
The Qaidam Basin in the Tibetan Plateau is an ideal place to examine the geomorphological process in arid area. Chronological data show that in the current deposition center of the basin the age of exposed fluvial strata could be 100 ka, due to differential wind erosion with stronger resistance to erosion. The wind deflated the surrounding fine-grain lacustrine deposits, and left the coarse-grain fluvial channels exposed. The widely distributed yadangs in this area are good evidence of wind erosion. The huge amount of deflated materials contributed significant dust source for the down-wind Loess Plateau.
The Yangtz River in China is an ideal place to examine this geomorphological process in the open fluvial system. High resolution chronological data on drilling cores in the Jianghan Basin (~700 km away from the delta) showed (1) low accumulation rate from 120 ka to 30 ka, (2) hiatus from 30 ka to 16 ka, (3) extreme high and continuous accumulation from 16 ka to 10 ka, and relative high and continuous accumulation afterward. This demonstrates the extremely rapid (even instant) response of a river system to sea level changes.
The geomorphological processes in both the Qaidam Basin and the Yangtz River fit well the pattern of the current hypothesis. It will be interesting to examine if this pattern exists in other parts of the Earth.