Abstract:

Zhujiang Formation is the provincial reservoir in Pearl River Mouth basin, and the cored section of Lower Zhujiang Formation (deposited from 23.8 to 18.5 Ma) of well LH-3 in eastern basin, consisting of terriclastic and carbonate rocks as well as mixed terriclastic-carbonate rocks, demonstrates a mineral series of anhydrite-limonite-kaolinite-dolomite from bottom to top, which also exist in adjacent wells, while the abundances are different. After the analysis of the material sources, formatting time and geological mechanism of these minerals, the authors draw the conclusion that all of the minerals formed in depositional of syn-diagenetic or pene-contemporaneous stage,  which reflects oxidized or even exposed environments during their formation. Furthermore, the mineral association can provide humidity information, as anhydrite and dolomite reflect the arid climate, while limonite and kaolinite indicate humid climate. After the integration of sponge and pollen data, carbon-oxygen isotopic data from neighbor wells, the authors know that the climate during the Lower Zhujiang Formation deposition have changed from arid and hot to humid and warm, then back to arid and hot again.

Key words: Pearl River Mouth basin, minerals series, diagenesis, paleoclimate, depositional system