Geochemical-mineralogical characteristics of the pre-Holocene sediments in Haenam Bay, west coast of Korea

Abstract

The geochemical and mineralogical characteristics of pre-Holocene core sediments from Haenam Bay, southwest coast of Korea, were examined for post-depositional diagenetic changes and used to assess the provenance of fine-grained sediments in the region. The geochemical and mineralogical compositions of the sediments vary very little with core depth (Holocene to pre-Holocene age), except for the upper part of the pre-Holocene sedimentary layer. In this case, smectite and chlorite are depleted, presumably due to intensive subaerial weathering and low pH conditions. Highly mobile elements (Ca, Mg, Na and K) were likely removed with the breakdown of labile minerals, such as carbonate minerals, feldspar, and clay minerals, during subaerial exposure of this layer, resulting in low weathering indices. In particular, the low smectite content (< 5%) and low V/Al ratio (< 13) suggest that the Holocene and pre-Holocene sediments along the southwestern coast of Korea did not originate from mainland China but rather mostly from the Korean Peninsula. This aspect has been a subject of debate since the mid-1970s.