The Cenozoic sediments in Zhujiangkou Basin disclosed in 7 offshore wells are dominated by clastic rocks with intercalations of combustible organic deposits in its lower and middle parts

the maximun thickness totals 3

350m.Ac-cording to the lithological characters and microfossils they contain

the Tertiarysediments can be divided into six stratigraphical units

in ascending order

theyare the Baoan Formation

Zhuhai Formation

Zhujiang Formation

Hanjiang Formation

Yuehai Formation and Wanshan Formation.The Baoan Formation and Zhuhai Formaton are characterized by abundant sporopollen

which may be distingushed into Taxodiaceaepollenites-Gothanipollis and Ostryoipollenites-Pinuspollenites assemblages aged to Oligocene.The Lower Miocene Zhujiang Formation contains calcareous nanofossils belonging to Sphenolithus belemnos zone and Helicosphaera ampliaperta zone

and Foraminifera of Globoro-talia jiaweiensis-Cassigerinella chipolensis assemblage.The calcareous nanofossils recovered in the Middle Miocene Hanjiang Formation are members of Triquetror-habdulus rugosus zone and Catinaster coalitus zone

which occur along with Foraminifera of Turborotalia siakensis zone.Abundant sporo-pollens belonging to two assemblages are also recovered in the Hanjing Formation

namely(in ascending order):Florschuetzia trilobata-F

semilobata

F.levipoli-Zonocostites of.ramonae.The Upper Miocene Yuehai Formation is characterized dominantly by coarse clastics

containing nanofossils of Discoaster quinqueramus zone and Amaurolithus amplificus zone

and Foraminifera of Ammonia altispira(nearshore) or Globigerina nepenthes zone(offshore). The nanofossils in the Pliocene Wanshan Formation are mainly preserved inits mid-lower parts

represented by Sphenolithus abies zone and Discoaster tamaliszone.The simultaneous Foraminifera is characterized by Globorotalia multicamerata-Sphaeroidinellopsis seminulina assemblage.Owing to regression

the upper part of the Wanshan Formation lacks calcareous nanofossils

but the benthic Foraminifera and Ostracoda are well developed.