Growth Fault

Growth Fault a fault in sedimentary rock that forms contemporaneously and continuously with deposition so that the throw increases with depth and the strata of the downthrown side are thicker than the correlative strata of the upthrown side. Growth faults are particularly common in areas of high sedimentation rate and are generally associated with thick deltaic successions.

Growth faults are relatively small, about 15 km to 20 km wide and 45 km to 50 km long. As sedimentation on the delta front is strongly influenced by relative change of sea level, it generally considered that sea level change also influences the formation of growth faults. Intense cyclonic storms may change sedimentation pattern near the delta lobes and may a effect the formation of growth faults. They are important for oil and gas exploration and development. Normally huge quantity of liquid and gaseous hydrocarbon deposits is found in traps associated with growth fault. Niger delta of Nigeria is a good example of oil and gas accumulation associated with them. In the Niger delta most of the hydrocarbons are produced from traps formed by displacement along growth faults.

No growth fault has yet been positively identified on the ganges-brahmaputra delta. However, this could indicate only small exploration activities. There are suggestions that growth faults are present, but till now they have not been positively identified. Offshore seismic survey from swatch of no ground indicates possible slump deposits on the delta front which could be associated with growth faults. As growth faults are linked with high sedimentation and slumping, chances of finding the same on the Ganges-Brahmaputra delta are good. Discovery of growth fault system will play an important role in future exploration for oil and gas in the Ganges-Brahmaputra delta. [Mahmood Alam]