Source tracing of tidal flats in Zhejiang coastal zone:evidence from magnetic mineral inclusions
Background,aim,and scope The tidal flat is important reserve land resource in Zhejiang coastal zone which are lack of flat land,and the abundant bench resource have always been regarded as the most important reserve land resources.Accurate tracing of the material source is an important basis for scientific management of tidal flats.Unlike the aeolian sediments,the tidal flat sediments may be partly dissolved through the transport and deposit processes,in turn,change the properties of sediments.Due to this,it is urgent to use the proxies,which are not affected by seawater dissolution,to accurately trace sources of tidal flat sediments in Zhejiang coastal zone.Materials and methods In this study,the magnetic characteristics of mineral inclusions were used to trace the source of Zhejiang coastal tidal flat,and then the material links between the tidal flat sediments in Zhejiang coastal,local river sediments,the Yangtze River sediments has been determined.Results The results shown that:(1)the main magnetic-carrying minerals is still magnetite in acid-treated samples;(2)the amount of magnetite within the host mineral in Zhejiang tidal flat sediments is very low,which only accounts 2%—8%of the original samples;(3)the proportion of hematite and magnetite in the magnetic-carrying minerals of acid-treated samples decreased significantly compared with the original samples.Discussion It has been found the magnetic parameters can clearly distinguish the sediments from Yangtze River and local river in Zhejiang.It indicates the magnetic characteristics of mineral inclusion is a good approach to trace the source of tidal flat sediments.Based on the scatter plot and fuzzy cluster analysis of xARM,SIRM and SIRM demagnetization parameters of acid-treated samples,the provenance of tidal flat was analyzed and discussed,which showed that they are mainly sourced from suspended particulates of local rivers.Conclusions Our study revealed that the magnetic properties of acid-treated tidal samples exhibited lower magnetite concentration and finer magnetic crystal particle size,which supports the materials of the tidal flat are mainly contributed by the local river sediments rather than Yangtze River sediments.Recommendations and perspectives These findings indicate the sediment supply in the coastal of Zhejiang will be stable and not decrease obviously,and the environmental magnetic characteristics of sediments is a reliable method that used for provenance tracing in the future.
mineral inclusionenvironmental magnetismtidal flat sedimentsfluvial sediments