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Ichnological constraints on the depositional environment of the Sawahlunto Formation, Kandi, northwest Ombilin Basin, west Sumatra, Indonesia

Elsevier Ltd
Publication Date
DOI: 10.1016/j.jseaes.2011.06.017
  • Sawahlunto
  • Arenicolites
  • Diplocraterion
  • Coenobichnus
  • Avian Footprint
  • Earth Science


Abstract A low diversity trace fossil assemblage is described from the Oligocene Sawahlunto Formation near Kandi, in the northwestern part of the Ombilin Basin in western Sumatra, Indonesia. This trace fossil assemblage includes six ichnogenera attributed to invertebrate infaunal and epifaunal activities ( Arenicolites, Diplocraterion, Planolites, Monocraterion/ Skolithos and Coenobichnus) and two ichnotaxa attributed to vertebrate activity (avian footprints: two species of Aquatilavipes). Arenicolites, Diplocraterion and Monocraterion/ Skolithos record the suspension feeding activities of either arthropods (most likely amphipods) or vermiform organisms. Planolites reflects the presence of an infaunal deposit feeder. Coenobichnus records the walking activities of hermit crabs. Both the Coenobichnus and the avian footprints record the surficial detritus scavenging of epifaunal organisms within a subaerial setting. These traces occur within a fine-grained sandstone succession characterized by planar laminae and low-relief, asymmetrical, commonly mud-draped (locally bidirectional) ripples. The presence of traces attributable to suspension feeders implies deposition in a subaqueous setting. Their occurrence (particularly the presence of Arenicolites and Diplocraterion) in a sandstone bed characterized by mud-draped and bidirectional ripples implies emplacement in a tidally-influenced marine to marginal marine setting. Co-occurrence of these traces with well-preserved avian footprints ( Aquatilavipes) further implies periodic subaerial exposure. Thus, it is most likely that the Sawahlunto Formation near Kandi records deposition within an intertidal flat setting. Definitive evidence of marine influences in the Oligocene interval of the Ombilin Basin implies a more complex tectono-stratigraphic history than has previously been implied.

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