Abstract:

The Hongshuizhuang Formation of the Jixian System in northernNorth China is a typical formation reˉlatively rich in organicmatter in theMesoproterozoic and theNeoproterozoic strata.ItsTOC can be up to13%-20%.Its features of lithologic cycle show that the Hongshuizhuang Formation shale was deposited in stagnant water bodywith weak horizontal circulation.And other characteristics such as organic carbon and sulfur content suggest that the formation contains highˉquality source rockswith large hydrocarbonˉgeneration potential.A study of the organic maceral characteristics of the formation indicates that theMesoproterozoic and the Neoproterozoic feature in single biotic formation，and that the organicmaceral compositions of theHongshuizhuang Formation are simple with alginite and sapropelinite debris in predom inance.The rapid increasing of alginite provide themateˉrial foundation for organic matter rich deposits.The discovery of provitrinite in the shale confirms the view that the provitrinite is of thallogen origin，providing an important clue for selecting thermal evolution parameters for the preˉDevonian marine strata.The existence of a large number of oil droplets in the shale cracks show that the organic matter of thallogen origin in theHongshuizhuang Formation had gone through effective hydrocarbon genˉeration and expulsion.The Hongshuizhuang Formation with an age over140Ma is the oldest organic rich deposˉits discovered so far in China that had experienced effective hydrocarbon expulsion.

Key words: organic carbon, provitrinite, marine vitrinite, maceral, Hongshuizhuang Formation, Mesoproterozoic, northern North China