Publications

Most of previous literatures have assumed that fluvial sedimentations reached their peak in low sea level conditions and that high sea levels were generally considered as a period of non-depositional and thus were ordinarily interpreted as an abandonment phase. In contrast, our recent findings from outcrop and subsurface data in the Lower Kutai Basin, East Kalimantan has revealed a complex response in the channel-fill development stages within marine transgression. Evidence has shown that some channels certainly “survived” the high sea level abandonment period. A three (3) km detailed transect was measured through several road cuts and coal mines in the Samarinda Anticlinorium area. The recent channel deposits in the Mahakam Delta and Balikpapan bay are also used as a comparative model. The well log, FMI, pressure analysis and core petrographical analyses permit an assessment of the subsurface pattern. The integrated biostratigraphy data (foraminifera, nanno-plankton and palynology) are used to synthesize the regional marker. This study also benefitted from unmanned aerial vehicle (UAV) mapping, which created a high resolution (1-3 cm precision) 3D digital outcrop model (DOM). These entire measurements and intensive amount of information are synthesized into the integrated geological model. We propose 3 new depositional models of transgressive channel due to their specific response at the channel upper boundary, namely: i) drowned fluvial channel, ii) backfilled/keep-up channel and iii) fluvial channel to shoreface rejuvenation. This study also reveals new insights about the sedimentary processes and facies geometries in the Lower Kutai basin. This unique phenomenon was affected by (a) a large tidal prism area that covers the entire delta systems and (b) a short (40-45 kilometers) fluvial to shelf sedimentation conduits, combined with (c) relatively high sedimentation fluxes. This new insight is noteworthy toward the reassessment of the geological model.