『Abstract
The Red (Hong) River straddles southwestern China and northern
Vietnam and drains the eastern Indo-Asian collision zone. We collected
bed sediments from its tributaries and main channel and report
the petrographic point counts of framework grains and major oxide
compositions as well as organic and inorganic carbon contents.
The Q:F:Rf ratios and Q:F:(L-Lc) ratios of
the bedload indicate quartz-poor, mineralogically immature sediments
of recycled orogen provenance. The weathering indices based on
major oxides - the chemical index of alteration (CIA) and the
weathering index of Parker - are also consistent with the recycled
sedimentary nature of the bed sediments. Using geographic information
system (GIS) we calculated for each sample basin such parameters
as temperature, precipitation, potential evapotranspiration, runoff,
basin length, area, relief, and areal exposure of igneous, metamorphic
and sedimentary rocks. Statistically meaningful correlations are
obtained between the two weathering indices, between CIA and sedimentary
to metamorphic rock fragments ratio, S/(S+M), and between CIA
and sedimentary rock cover, but otherwise correlations are poor.
The bed sediments preserve signatures of their provenance, but
the effect of weathering is not clearly seen. Subtle differences
in the bed sediments are observed between the Red and the Himalayan
rivers (Indus, Ganges, and Brahmaputra) as well as between sub-basins
within the Red River system and are attributed mainly to differences
in lithology.
Keywords: Tibet; Da; Lo; Climate; GIS; Chemical index of alteration』
1. Introduction
2. Geological and hydrographical setting
3. Materials and methods
4. Results
4.1. Petrography
4.2. Major oxides
4.3. Organic and inorganic carbon
4.4. Weathering indices
4.5. Relationship to climate, geomorphology, and lithology
5. Discussion
5.1. Seasonal, downstream, and interbasin variations
5.2. Comparison to the Himalayan rivers
6. Conclusions
Acknowledgments
References