Abstract:

Newly discovered exploration development zone locates at the Bel-Lake depression in Mongolia. Early Cretaceous vertical filling and evolvement suite research indicate that large scale of syn-sedimentary  fault system mode and distribution control the sedimentary  tracts of fault depression basin in the Earlier Nantun Group strata. The depression filling and evolvement suite indicate that act-fracture action and dextral strike-slip of basin play an important role in sedimentary system evolvement. Long-lasting active syn-sedimentary faults system as well as tectonic dextral strike-slip controls the forming and distribution of construction palaeogeomorphology, fracture sloping and ramp zone, thereby, which further controls coarse clastic sedimentary system development and distribution mode. The north edge fracture slope zone of east sub-depression often controls the coarse clastic sedimentary system of deposition and depocentre. Especially the nearshore subaqueous fan within low system tract , which are the most favorableness zone for sandstone reservoir. Syn-sedimentary faults have various of combination of styles including “ren” or “zhi” characters shape etc. have bring up changing construction palaeogeomorphology and ramp system which control the sandbody decentralized system and the accumulation mode. Revealing synsedimentary faults zone activity and distribution and rebuilding each stage of construction palaeogeomorphology and ramp zone are the key to the prediction of sedimentary system distribution and sandbody distribution.

Key words: dextral strike-slip, fracture action, filling sequence, ramp zone, Early Cretaceous, Bel-Lake depression, Mongolia