Cyclic Steps at the Channel-Lobe Transition Zone in Offshore Mozambique, East Africa

Abstract

In deep-water system, the zone connects channels and lobes, named channel-lobe transition zone (CLTZ), is highly important to understand the evaluation of submarine fans, but has been difficult to study. Because it’s a dynamic depositional environment and seldom preserved over geologic time scales unless it is accompanied by rapid aggradation of the overlying submarine-fan system. But it will be easier if it is investigated from modern seafloor with high resolution dataset. Here we use a high-resolution (~45 Hz) three-dimensional seismic-reflection data to interpret the stratigraphic architecture of channel-lobe transition zone at modern seafloor in offshore Mozambique. Step-like features are founded within CLTZ and investigated through high-resolution seismic data. These features rang from 500 to 700m in wavelength and 15-30 m in wave height, are interpreted as cyclic steps formed by turbidity currents flowing through the channel. The interpretation is mainly based on their step-like morphology, large aspect ratios (ratio of wavelength to wave height), and typical upstream migration characteristic through backset bedding from seismic profile. The average slope gradient for the cyclic steps develop area is about 2.4°. We expect that within this high resolution seismic data, the 3D characteristic (from plain view to profile) of cyclic steps developed in CLTZ, could provide a better understanding of the reservoir characterization in continental margins with rapid aggradation of a submarine-fan system. In these settings, high gradients and sediment supply can promote coarse-grained turbidite deposited at slope breaks where hydraulic jumps happen.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018