Three-Dimensional Nature of Channelforms in Recent Sequences of the Sunda Shelf, Indonesia

Brian Kiel and Lesli Wood
Bureau of Economic Geology, Jackson School of Geosciences University of Texas at Austin, Austin, TX

The Sunda Shelf of Indonesia is an important physiographic link between the South China Sea and the Indian Ocean. However, little knowledge exists on how the region has responded geomorphologically to dramatic changes in climate and sea level in the past several 100,000 years. An exceptional-quality, large (~3,200-km²) 3D seismic data volume was used to establish a framework of geomorphologic development across this recent shelf and to examine how neotectonics have affected the depositional systems. Thirteen gamma logs provided some lithologic control, but no age control. Exceptionally complex but well-imaged channels and associated architecture, on the other hand, enabled calculations of channel-flow properties that could shed light on dynamic climate processes, including the Indian Monsoon. Spatial analysis of depositional elements also provided a data set for stochastic modeling of deeper gas reservoirs.

Mapping shows that the shelf has been tectonically active, undergoing compression up until very recently. Numerous complex channels have occupied the study area in response to deltaic regression across the shelf during the last glacial lowstand. Early sequences show channelized phases punctuated by shelf-sand development during high-frequency transgressions. Logs indicate a strong increase in sand content in more recent systems. Density of channeling in the strata has increased over time, progressing from single, large, well-formed valleys into high-density systems. Significantly different channel morphologies form adjacent to one another simultaneously. Channelforms include meandering, straight, braided, and anastomosing, as well as single- and multiple-phase systems.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas