Abstract: It is disputable about whether the eastern provenance exists for the Pinghu Formation in the Xihu sag. Its clear answer will be signifcant for hydrocarbon exploration. Based on drilling, seismic, and test data, the Pinghu Formation sediments were analyzed in respect of ZTR index of heavy minerals, sandstone types, debris composition, sandstone content, seismic facies and syndepositional structural features. It is found that the ZTR index of terrigenous heavy minerals and the maturity of sandstone components in the Pinghu Formation are "low at both sides of the sag and high in the middle", while the contents (or percentages) of siderite (an authigenic heavy mineral) and sandstone are "high at both sides of the sag and low in the middle". According to seismic reflection features, the Pinghu Formation has apparent chaotic reflections at basin margin and prograding reflection confguration that indicates the existence of the eastern provenance. Moreover, the existence of growth anticlines during middle-late stage of the Pinghu Formation further proves, from the prospective of tectonic stress, that there was an eastern folded and uplifted belt during the sedimentation of the Pinghu Formation. It is concluded that the eastern folded and uplifted belt had already uplifted and become the eastern provenance during the sedimentation of the Pinghu Formation. The deep Pinghu Formation in central and eastern parts of the Xihu sag has good hydrocarbon exploration prospect.

Key words: ZTR index, seismic facies, Xihu sag, Pinghu Formation, provenance analysis