Tectono-Sequence Stratigraphic Analysis on Paleogene Shahejie Formation in the Banqiao Sub-Basin, Eastern China

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Ed of the Dongying Formation is related to the late rift stage. The tectonic activity in the Banqiao sub-basin decreases slowly. Here only small number of low-stand fans forms. However, incised valleys and large scale low-stand wedges are the main features of the low stand system tract. Furthermore, in the 3rd order sequence, the high stand system tract became more important. It is dominated by a lacustrine delta. Main sediments supply was the Cangxian uplift but the Beidagang buried hill didn’t supply any because it was submerged at this phase.

The downthrown block of the Cangdong fault and Haihe fault is the place where mainly fan-delta depositional systems forms. In addition, at the fan-delta plain setting mud flow deposits are common. Not only that, the sediments is largely made of conglomerate which are poorly sorted and gravel clast which are subangular, subspherical and poorly oriented. The submerged part of fan-delta is represented by the fan-delta front deposits. The submerged part includes subdistributary channel, mouth bar and distributary bay.

Next, the northeastern margin of the Shenqingzhuang buried hill to northwestern margin of the Beidagang buried hill is the place where braided-delta depositional system is formed. This delta is a coarse delta and has coarse particles. Moreover, it has the drag flow characteristics. The main sediment bodies of this delta is made of braided distributary channel deposits. This shows that the delta has more sustained currents and better continuity. The braided-delta front is made up of distributary channel, mouth bar and interdistributary bay deposits.

Lastly, the downthrow block of the Cangdong fault in the Xiaozhan area is the area where the nearshore subaqueous fan develops. Coarse pebbly sandstone is the main lithology for this area. Along a belt from Shanggulin to Lvjuhe, deep water turbidite fans are formed. The lithology that we can find hereis coarse deep sea turbidite sandstone interbedded in thick lacustrine mudstone. From here we know that sediments are delivered from delta to depocenter frequently.

HYDROCARBON POTENTIAL

Bohai Bay basin which is one of the prime petroleum basin. It has the hydrocarbon potential according to researches. More studies are being done to dig more information of this hydrocarbon potential basin.

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