Taphonomy of larger foraminifera: Relationships between living individuals and empty tests on flat reef slopes (Sesoko Island, Japan)

Abstract

The depth distributions of larger foraminifera (27 species) were investigated along two transects in the fore reef areas of a NW Pacific fringing reef. One transect is distinguished by a strong flattening below the steep reef slope (−30 m), whereas further steepening characterizes the equivalent part in the other transect. According to the different taphonomic processes affecting foraminiferal tests before final sedimentation, empty tests were classified into the three categories ‘optimally’, ‘well’ and ‘poorly’ preserved. The depth distribution of each preservation state was compared with living individuals. While distributions of optimally preserved tests almost coincide with living individuals, well-preserved tests are characterized by significant depth shifts that are stronger at the upper-most slope compared with the deeper parts. Since the time-averaged traction forces are similar in both investigated transects, differences between the distributions of living individuals and well-preserved tests are more intensive on steep versus flat slopes. Poorly preserved tests signalize allochthonous origin or reworking of relict sediments.