Magnetism parameters characteristics of drilling deposits in Jianghan Plain and indication for forming of the Yangtze River Three Gorges

Abstract

The forming time of the Yangtze River Three Gorges is considered as one of keys in the research on the Yangtze River, also is one of the most disputed hotspots. In order to solve the difficult problem, the authors adopt the internationally recognized thoughts and methods of substance tracing from source to sink. The lithologic characteristics, magnetic parameters and magnetic mineral characteristics of deposits in 2 bores are analyzed, which are both sampled from the sedimentary center of the Jianghan Plain. The results are as follows: At about 110 m depth of the core, the contents of coarse materials and stable magnetic mineral both increase significantly. Meanwhile, the magnetic susceptibility of sediment, saturation isothermal remanent magnetization and magnetic susceptibility values of anhysteretic remanent magnetism increase suddenly, which all reflect that at about 110 m depth, the important adjustment has appeared in water system of the Jianghan Plain, and the sedimentary environment and material composition have changed greatly. And it may be the horizon where the Yangtze River Three Gorges formed, its forming time reflected by the paleomagnetic dating is between 1.17 and 1.12Ma B.P.Yangtze River, forming of the Three Gorges, sediment of the Jianghan Plain, magnetism parameters and magnetic mineral characteristicsThe formation of theYangtze River is the basis for many great scientific issues, and the forming of Three Gorges considered as one of keys in the research into the formation of the Yangtze River, also is the most disputed hotspot in the research of the Yangtze River. As early as the beginning of the last century, it had attracted great attention of many notable scholars from China and abroad, such as Willis [1] , Barbour [2] , Li Siguang [3] ,Ye Liangfu and Xie Jiarong [4] , Li Chunyu [5] . But previous research focused on geomorphology, for example, the height and order of terrace and planation surface, methods of regional geology and geotectonic evolution [6] , the sediment characteristics were less involved, especially research on magnetic susceptibility characteristics of deposits. Because of complexity and multiplicity in geomorphological classification and effects of regional geology and geotectonics, although the research has lasted about a century, the different views on the forming time still remain [1][2][3][6][7][8][9][10][11][12][13] . With the Jianghan Plain (Basin) as a direct unloading area after the Yangtze River cut the Three Gorges, its deposits must record the information of forming the Three Gorges, so the authors adopted the internationally recognized thoughts and methods of substance tracing from source to sink, and selected 2 representative bores as targets to discuss the formation of the Yangtze River Three Gorges through provenance analysis on magnetic susceptibility change, susceptibility characteristics of deposits, as well as characteristics of bore and grain size of sediments and magnetic mineral.

Neodymium isotopic variations of the late Cenozoic sediments in the Jianghan Basin: Implications for sediment source and evolution of the Yangtze River

“…Although study of the evolvement of the Yangtze River has a long history of more than 100 years, it is still controversial. Previous studies proposed that the Yangtze River can be dated back to the Cretaceous or the early Tertiary (Clark et al, 2004;Clift et al, 2006Clift et al, , 2008bJia et al, 2010;van Hoang et al, 2009), the early Quaternary (Fan et al, 2005;Kang et al, 2009;Yang et al, 2006;Zhang et al, 2008) or the late Pleistocene (Brookfield, 1998). Clark et al (2004) proposed that the Yangtze River was once the tributary of the so called ''paleo-Red River'' draining into the South China Sea and reorganized by sequential river capture and reversal events.…”

Detrital zircon geochronology and provenance of core sediments in Zhoulao Town, Jianghan plain, China

“…The sand sample Gsh-6 was recovered from a depth of 86.76-88.58 m. The paleomagnetic age of Gsh-6 is about 800 kaBP (Zhang et al, 2008).…”

“…We choose this sample because it is near the turning point where the contents of coarse materials and stable magnetic mineral both increase significantly; meanwhile, the magnetic susceptibility of sediment, saturation isothermal remnant magnetization and magnetic susceptibility values of anhysteretic remnant magnetism increase suddenly (Zhang et al, 2008). Zhang et al (2008) considered that at about 110 m depth, the important adjustment appears in the water system of the Jianghan plain, and the sedimentary environment and material composition change greatly.…”

“…Zhang et al (2008) considered that at about 110 m depth, the important adjustment appears in the water system of the Jianghan plain, and the sedimentary environment and material composition change greatly.…”

Sr-Nd isotope stratification along water depth: An example from Datong hydrological station of Yangtze River

“…A large variety of methods, such as elemental and isotopic geochemistry [1][2][3][4][5][6][7][8], heavy mineral [9,10], magnetic mineral [11][12][13], U-Pb dating of detrital zircons [14,15] and some other methods play an important role in provenance investigations of river sediments. Among these methods, Sr-Nd isotopic systemis widely applied to provenance study of rivers since they basically do not fractionate during weathering, erosion and transport.…”