Distribution pattern and controlling factors of heavy mineral assemblages in surficial seafloor sediments offshore of the Eastern Shandong Peninsula (Yellow Sea)

The source and processes controlling the deposition of the sand fraction of muddy seafloor sediments remain poorly understood. Surficial seafloor sediments were collected offshore of the Eastern Shandong Peninsula and were analyzed regarding their detrital heavy mineral constituents and grain size distributions to determine their spatial distribution patterns, sand fraction provenance, and transport pathways. Five sediment types were identified in the study area: clayey silt, silt, sandy silt, silty sand, and sand. Each of these sediment types displayed distinct grain size parameters of their corresponding sand fractions. Moreover, three statistical clusters of sand grains were identified, suggesting variations in provenances and sedimentary processes from one cluster to the next. Twenty-five species of detrital heavy minerals in the sand fraction were identified and then assigned to four categories based on their mineral stability (i.e., ultrastable, stable, moderately stable, and unstable). The sandy sediments were enriched in ultrastable and stable heavy minerals, indicating that these sand grains mostly originated from coastal erosion of granitic and/or metamorphic rocks. In contrast, the muddy sediments were characterized by unstable heavy minerals dominated by hornblende and epidote. The results of principal component analysis further suggested that these sand grains are similar in terms of their provenance (coastal erosion) but have undergone complex sedimentary processes. Relative sea level changes during the late Quaternary caused shifts in the sediment sources and supplies, which were the primary factors controlling the grain sizes of the sand fractions and heavy mineral assemblages in the surficial sediments of the study area.