Publications

Detailed stratigraphic evaluation of 3D seismic data from the Miocene section of the offshore northwest Java shelf reveals the extensive presence of preserved shelf ridges. These features are deposited as long linear bodies ranging from 0.3 to 2.0 km wide, over 20 km long, and up to 17 m high. Upon closer inspection, these features appear to be asymmetric, characteristically sharp-edged and thicker on one side, gradually thinning with an irregular edge on the other side. Possible sand waves, smaller in scale, are observed superimposed upon these ridges and oriented oblique to the long axes of the ridges. Shelf ridge deposits tend to be sand prone and are observed to overlie ravinement surfaces. The ridges appear to be oriented parallel to paleo trunk valleys associated with broad structural embayments. In addition to shelf ridges, shelf ribbons, possibly less than 5 m thick and less than 100 m wide, are also imaged.Sand ridges are common on modern shelves, but rarely observed in the subsurface or in outcrop. The features observed here represent rare unequivocal examples of preserved ancient shelf ridges. These ridges are thought to have formed as a result of erosion and subsequent reworking of sand-prone delta plain and/or coastal plain deposits by shelf tidal currents that became active immediately after shoreline transgression. They appear to have migrated across the ancient sea floor and represent a significant component of the transgressive systems tract.These transgressive systems tract deposits have significant exploration potential insofar as they are commonly sand prone and they tend to be encased in shelf mudstone seal facies. Depending upon the degree to which sand is present in inter-ridge locations, these linear sand bodies can comprise potential stratigraphic traps.