Magnetic properties of coastal loess on the Midao islands, northern China: Implications for provenance and weathering intensity

Abstract

Loess deposits are widely distributed over the islands in the Bohai Gulf and neighboring regions of northern China. The coastal loess, located to the east of the Chinese Loess Plateau (CLP), is believed to have a local source from exposed marine sediments and a distant source from inner arid regions in Asia. In this study, magnetic, geochemical and diffuse reflectance spectroscopic analyses were conducted on the loess to explore its relationship with the loess on the CLP and its paleoclimatic implications. We find that the coastal loess shows similar geochemical composition, background susceptibility and magnetic enhancement to loess on the CLP. Magnetic minerals characteristic of pedogenesis are more important in the paleosol layer, with fine ferrimagnetic minerals abundant in paleosol layer SB1 and hematite in paleosol layer SB2. Geochemical evidence suggests that weathering intensity in paleosol SB2 is similar to or even stronger than in paleosol SB1. Pedogenic enhancement of magnetic susceptibility in the study area is not so strong, which may be due to enhanced hematite formation as opposed to ferrimagnetic mineral production and preservation.