Seismic sequence stratigraphic and depositional framework of the Miocene sediments in Offshore Indus, Pakistan.

Regional seismic data with deep wells information has been used to interpret the depositional setting of Miocene sediments in the Offshore Indus Basin, Pakistan. The current study has implications for understanding the complex subsurface geology of the Offshore Indus Basin, Pakistan. Two seismic profiles were selected to interpret the sedimentary packages within the Miocene sediments. The interpreted seismic data showed four different recognizable system tracts in the Miocene sediments. These include Lowstand, Highstand and Falling Stage System Tracts. The sedimentary packages differ in regional setup depending on the location within the offshore basin. The eastern part (as highlighted by seismic Profile-2 and Profile-3) exhibits more complex sedimentary geometries in comparison to western part (as highlighted by seismic Profile-1). The earlier deposition is controlled by lowstand settings when the sea-level dropped below the shelf margin leading to incision over the shelf. This led to the deposition of Lowstand fan systems. This was followed by a rise in sea-level leading the way for the carbonate deposition over the shelf. An intermittent unconformity is identified by another set of lowstand fans and truncation patterns. This unconformity halted the carbonate deposition over the shelf and transported the sediments to the basin floor. Later, rise in sea-level resumed the carbonate deposition over the shelf. Another sea-level drop is noticed and sediments are interpreted to be moving towards the basin leading to a Falling Stage System Tract and easily identified by regressive onlaps. This unconformity is more pronounced towards east where it eroded the carbonates. Downlaps seen above this unconformity confirm the deepening conditions leading the way for the deposition of finer sediments. Further drop in sea-level is seen leading the way for coarse sediment deposition. We believe that this study would provide strong support for researching global passive margins from economic perspective as well as understanding complex depositional framework. [ABSTRACT FROM AUTHOR]