Seismic sequence stratigraphy and depositional history of the Pliocene-Pleistocene fans in the Ganal Block, offshore Kutai Basin, Indonesia.

摘要

A seismic stratigraphy study was conducted to develop a stratigraphic framework for Pliocene-Pleistocene sediments in the Ganal area, Makassar Strait, Indonesia. The study area, physiographically located in the continental slope of the offshore Kutai basin, is very attractive for deep water sequence stratigraphy analysis. The sediment interval exhibits a series of geologic features of deep water sedimentation such as a submarine fan associated with canyons and channels-levees complex. Analysis of over 4000 km of multichannel seismic data serves to detail documentation of such features and the stratigraphic evolution of the area.; On the basis of their termination patterns, two types of significant stratigraphic surfaces, unconformity and flooding surfaces, can be identified as seismic boundaries on the seismic sections. The unconformity surfaces can be recognized by erosional, truncation, and onlap termination patterns. The distribution of these surface can be correlated in the area from the slope to the basin floor, which is commonly associated with scour channels. The flooding surfaces can be recognized by downlap termination patterns of the younger layers into the older strata below. Both of these surfaces provide important information to reveal the depositional history of the deep water sedimentation in the study area.; Regional seismic profiles indicate that the Pliocene-Pleistocene sediments were deposited in the slope to basin floor setting, from the west to the east respectively. The structural and stratigraphic analysis suggests that this basin configuration strongly influenced the distribution and thickness of the seismic sequences and stratigraphic development of the Pliocene-Pleistocene sedimentary succession. Isochron maxima correspond to the depocenters that are close to sedimentary pathways and are associated with submarine channels and canyons. The isochron patterns show that depocenters and sediment pathways during deposition of the Pliocene-Pleistocene interval coincide with regional basin setting.; Six seismic sequences have been identified within the Pliocene-Pleistocene interval. Each sequence consists of lowstand deposits that can be recognized by its seismic facies units. The seismic characteristics vary from sequence to sequence as well as within lowstand system tracts. Lowstand features including submarine canyons, channels, and fan lobes have been identified and mapped. Identification of these features substantially reduces the reservoir risk associated with deep water depositional environments.; The canyons, channels, and fan lobes in the study area were superimposed and presented in the composite map and served as a good model and unique example for deep water sedimentation. Finally, a depositional model of lowstand deposits for the study area has been established and may play an important role in future exploration and development in this region and elsewhere in the world.