Ichnofabric oscillatory curves reveal the tide-dominated depositional system in Samarinda, Kutai Basin (Indonesia)

Since the interaction of fluvial, wave and tidal processes was proven in Samarinda, Kutai Basin (Indonesia), then the interpretation of the depositional system lead to a deltaic system. However, interpretation of depositional system remained a challenge, because other systems (e.g., estuary, strandplain and lagoon) could be formed within a deltaic system. Here, we demonstrate the testing by ichnofabric methods to reveal the paleoenvironmental processes in a deltaic system. The bioturbation index (BI), ichnodiversity (ID), number of behavior (NB), penetration depth (PD), ichnofossil diameter (Dm), in ichnofabric units were scrutinized. The data were processed by principal component analysis (PCA). The main findings were (1) the PC-1 and PC-2 oscillatory curves, and (2) the phase between PC-1 and PC-2 curves (i.e., out of phase and in phase). The PC-1 curve was loaded by BI, ID, and NB and the PC-2 was loaded by PD and Dm. The generated curves were interpreted as the indicators of colonization window, organism mobility, and space using by the organism. The oscillatory curve suggested how the organism interact with the substrate are repeated. In conclusion, the generated curves associated with the change of the intensity of fluvial, tidal, and wave processes that occurred in tide-dominated depositional systems.