Age and paleo-environmental evolution of the Douala Basin (Cameroon) during the Cenozoic: insights from palynology and sequence analysis

Abstract

The Douala basin in Cameroon is one of the West African basins created during the opening of the South Atlantic Ocean after the break-up of the Gondwana superstructure. Until now, no detailed studies of age and paleo-environmental evolution of this basin during the Cenozoic have been carried out, especially on outcrops sections. Palynological and sequence analyses have been performed on the outcrops in the Missole I and Dibamba localities in the central part of this basin. This integrated approach allow us propose a new age and paleo-environmental evolution of the Douala Basin. Three palynomorph assemblages have been identified: (i) the Paleocene-Eocene palynomorph assemblage ( A) from the Missole I deposits; (ii) the Oligocene palynomorph assemblage ( B) from the lower part of the Dibamba deposits; and (iii) the Lower to Middle Miocene palynomorph assemblages ( C) from the upper part of the Dibamba deposits. Sequence analysis indicates four depositional sequences with a vertical succession, characterized by major transgressive depositional sequences (depositional sequence “a”, “b”, and “c”), and a minor regressive depositional sequence (“d”). The trangressive sequences were deposited in lagoon or marginal marine environments during Paleocene-Eocene, while the regressive sequence was deposited in prograding continental shelf during the Oligocene-Middle Miocene. The recognized depositional sequence and associated depositional environments were controlled by spasmodic subsidence, margin uplift and climatic variations. Climate evolved from a wet-dry subtropical to tropical during the Paleocene-Eocene and a warm humid subtropical during the Oligocene up to Lower Middle Miocene with overall shift of the Douala basin from the Southern to the Northern hemisphere. This study reveals the existence of Oligocene deposits (Souellaba Formation) in the outcrops and could be useful for future correlation with the offshore part of the Douala Basin.

Palaeoenvironment of the Albian‐Cenomanian Mundeck Formation in the Douala Basin (SW, Cameroon): Evidence from facies analysis and geochemistry

“…The drift II phase (Eocene to present) is marked in this basin by a regressive period, which created an erosional unconformity on the top of the N'Kapa Formation. This unconformity is overlain by marls with some sandstone intercalations of the Souellaba Formation (Mfayakouo et al, 2021; Nguéné et al, 1992). These deposits were followed by a prograding deltaic succession, characterized by yellow sandstones and variegated clays interstratified with volcanic deposits of the Matanda Formation.…”

“…These deposits were succeeded by the Campanian to Maastrichtian deposits (Logbaba Formation), which consist of basal clayey marls and turbidites. This sedimentary succession is in turn overlain by shales, marls, limestones, fine to coarse-grained, cross-stratified sandstones intercalated with kaolinitic sandstones, bituminous shales and ferruginous sandstones (N'Kapa Formation) dated Palaeocene to Eocene (Mfayakouo et al, 2014(Mfayakouo et al, , 2021Njike Ngaha et al, 2014).…”

“…It displays some local differences in the lithological aspect, the similar structural and stratigraphic characteristics, with tectonic evolution which is subdivided into three classical stages commonly associated with the evolution of the passive margin, namely: the pre‐rift stage, the syn‐rift stage and the post‐rift stage (Brownfield & Charpentier, 2006; Nguéné et al, 1992; Reyre, 1984). Only the syn‐rift and post‐rift stages have been mentioned in the Cameroonian epicontinental basin with sedimentary succession which has been dated from the Lower Cretaceous to the present (Manga, 2008; Mbesse et al, 2021; Mfayakouo et al, 2021; Nguéné et al, 1992; Reyre, 1984). The sedimentary succession of the syn‐rift stage (Lower to mid‐Cretaceous) in the Douala Basin as well as in the West African margin basin has attracted the attention of the petroleum companies because of the presence of source rock and other elements of the petroleum system as reservoir and seal (Brownfield & Charpentier, 2006; Ntamak‐Nida et al, 2008; Pauken, 1992; Yugyè et al, 2021).…”

“…Only the syn-rift and post-rift stages have been mentioned in the Cameroonian epicontinental basin with sedimentary succession which has been dated from the Lower Cretaceous to the present (Manga, 2008;Mbesse et al, 2021;Mfayakouo et al, 2021;Nguéné et al, 1992;Reyre, 1984). The sedimentary succession of the syn-rift stage (Lower to mid-Cretaceous) in the Douala Basin as well as in the West African margin basin has attracted the attention of the petroleum companies because of the presence of source rock and other elements of the petroleum system as reservoir and seal (Brownfield & Charpentier, 2006;Ntamak-Nida et al, 2008;Pauken, 1992;Yugyè et al, 2021).…”