TROPICAL GEOGRAPHY ›› 1993, Vol. 13 ›› Issue (4): 335-343.

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NEOTECTONIC UPLIFT MOVEMENT:A BACKGROUND FACTOR LEADING TO SOLL AND WATER LOSS——A CASE STUDY OF THE MOUNTAINOUS REGION IN EAST GUANGDONG, SOUTH CHINA

Xie Ming   

  1. Institute of Soil Science, Guangdong Province, Guangzhou, 510650
  • Received:1993-03-01 Online:1993-10-30 Published:1993-10-30

Abstract:

The mountainous region in East Guangdong,South China,is an intermittently neotectonic uplift zone with main characteristic of fault-block movement.In this zone the effects of neotectonic uplift movement(NUM)on soil and water loss(SWL)are as follows:(1)NUM has controlled distribution of SWL over a wide range.In a zone where neotectonic uplift amplitude is great,generally speaking,the ratio of SWL area to mountainous region in this zone is large.(2)NUM brings about headward erosion.According to the formation and distribution of slope disintegration—the most serous type of SWL on weathered granite crust in South China,undoubtedly,it is the headwaters of headward erosion on the weathered granite crust in South China,and its growth is the process of headward erosion.(3) From stratified relief which is the outcome of NUM,SWL (especially slope disintegration) mainly occurs on lower planation surface usually with an altitudes of 200—300m. It is because that lower planation surface is in the stage of desintegration.In the author's view NUM has provided other factors leading to SWT with facility that is cutting down local base level,hence,NUM is a background factor leading to SWL.It is significant to understand this background factor for soil and water conservation (SWC) in neotectonic uplift zone:(1)In accordance with the theory of marcogeologiczl cycle, SWC is a mankind's activity to resist a certain exogenic force,and it is a certain anti-process influenced by anthropolfactor within macro-geological cycle too.Therefore,SWC is an arduous task for a long time to come.(2)The measures of SWC must be aimed at lifting up local base level.(3)Under the background factor of NUM,there are no measures of SWC whatsoever fully to keep off the loss of surface matter,and then,if SWL is reduced to such an extent that it will never or hardly again endanger normal anthropolgenic activity, its volume is regarded as "loss tolerance"(or "acceptable erosion").SWL sould be limited below "loss tolerance". On the author's calculation,the modulus of "loss tolerance" is about 350 t/km2·a),or the depths of "loss tolerance"is about 0.26mm/a in the mountainous region in East Guangdong.

Key words: Neotectonic uplift, Soil and water loss, Headward erosion, Loss tolerance, South China