Facies Analysis and Sequence Stratigraphy of Missole Outcrops: N’Kapa Formation of the South-Eastern Edge of Douala Sub-Basin (Cameroon)

Abstract

Missole facies description and sequence stratigraphy analysis allow a new proposal of depositional environments of the Douala sub-basin eastern part. The sediments of Missole outcrops (N’kapa Formation) correspond to fluvial/tidal channel to shallow shelf deposits with in some place embayment deposits within a warm and semi-arid climate. Integrated sedimentologic, palynologic and mineralogical data document a comprehensive sequence stratigraphy of this part of the Douala sub-basin. Five facies associations occur: (1) facies association I is characterized by Floodplain deposits; (2) facies association II is Fluvial to mouth bar deposits; (3) facies association III characterise Shallow Shelf deposits; (4) facies association IV represents Distal bay or Lacustrine deposits; and (5) Facies association V is made of Fluvial channel deposits. Six depositional sequences were identified. These sequences are composed of four progradational sequences and two retrogradational sequences containing a fluvial channel portion represented by lag deposits at the base of retrogradational sequences. These deposits represent the outset of the relative sea level rise period. In the study area, the N’kapa Formation is composed of non-marine/coastal aggradational deposits representing the early stage of the regressive period. The occurrence of the estuarine/bay deposits with paleosols development is interpreted as evidence of climate change with significant relative base level fluctuation. The study of key minerals associated to sequence stratigraphy as well as palynology demonstrated that sequence architecture has been controlled mostly by climate evolution and outcrops are dated Paleocene – early Eocene.