Abstract:

The faulted-topographic break zone is a zone of depositional slope with apparently abrupt-change caused by longtime activities of homo-depositional tectonics.A lowstand fan of the zone mainly consists of underwater alluvial fans,larger turbidite fans, smaller lowstand delta and lowstand fan delta.Lowstand turbidite fans in the steep gradient zone and distant part of the fan-shaped delta are distributed in low terrace,and main body of the fan-shaped delta and the incised-valley fillings are distributed in high terrace while near shore part of the delta and the alluvial fans are developed in higher terrace.During quick subsidence of the depositional base-level,continental incised-channels were formed on the slow slope zone and underwater alluvial fan bodies were developed down below the slope.When the base level was slowly uplift,incised channel fillings were formed on the faulted topographic break zone and down below the zone underwater alluvial fan sandbodies and distant turbidite fan bodies were developed.It is believed that original subtle litho-reservoir could be easily formed in lowstant fans of the faulted-topographic break zone.This kind of reservoir is characterized by its closer distance to source rocks,by well-developed porosity and by superior dredging conditions.

Key words: faulted-topographic break zone, Lowstand fan, origin, reservoir