We present the results of rock magnetic, granulometric, microscopy and mineralogical analyses of shelf sediments off Krishna, Godavari, and Mahanadi Rivers, Bay of Bengal. The aim of the study was to assess the influence of contrasting lithologies and hydrodynamic controlled grain size fractionation processes on the magnetic properties of shelf sediments. Sediment magnetic mineralogy mainly consist of ferrimagnetic titanomagnetite grains of detrital origin with variable concentrations and grain sizes. A clear trend of alongshore (SE - NW directed) decrease in magnetite concentration followed by fining of magnetic grain size can be attributed to the enhanced change in magnetic contribution from Deccan basaltic (mafic) to granitic (felsic) gneissic dominated sediment province coupled with differential sediment fluxes at each site. Bivariate plot of magnetic and grain size parameters clearly records such shift in sediment provenance and differential transport mechanism of magnetic particles at the studied sites. Magnetogranulometric ratio (ARM/IRM) positively correlates with the magnetite content in majority of the studied samples. Higher magnetic susceptibilities were found associated with coarser magnetic particles. Granulometry of the magnetic fraction showed that magnetic grain size is independent of physical grain size above >40 μm. The non-monotonous relationship between the magnetic and physical grain size can be explained by the fact that few individual finer particles occurred as magnetic inclusions protected within host (coarser silt and sand) fractions. Rockmagnetic and granulometry based approach presented in this study bears high potential for efficient tracking of sediment provenance and fractionation mechanism of magnetic particles in the shelf system, where contrasting sediment sources and complex transport dynamics create a large variability in magnetite content and grain size.

我们介绍了孟加拉湾克里希纳，戈达瓦里和马哈纳迪河沿岸的陆架沉积物的岩石磁学，粒度分析，显微学和矿物学分析结果。该研究的目的是评估对比岩性和流体动力学控制的粒度分级分离过程对陆架沉积物磁性的影响。沉积物磁性矿物学主要由碎屑来源的亚铁磁性钛磁铁矿晶粒组成，其浓度和晶粒尺寸各不相同。沿磁铁矿浓度（SE-NW定向）的沿岸下降趋势明显，随后细化了磁性晶粒尺寸，这可以归因于Deccan玄武质（镁铁质）对花岗质（长英质）片麻质岩为主的沉积物省的磁作用变化增强，再加上差异化每个站点的沉积物通量。磁性和粒度参数的双变量图清楚地记录了研究地点的沉积物产地偏移和磁性颗粒的差异输运机理。在大多数研究样品中，磁法比（ARM / IRM）与磁铁矿含量呈正相关。发现较高的磁化率与较粗的磁性粒子有关。磁性级分的粒度分析表明，大于> 40μm的磁性晶粒尺寸与物理晶粒尺寸无关。磁性和物理晶粒尺寸之间的非单调关系可以通过以下事实来解释：几乎没有单个细小颗粒作为受磁夹杂物存在于主体（粗粉砂和沙子）级分中的磁性夹杂物而出现。