Contents lists available at ScienceDirect Journal of African Earth Sciences journal homepage: www.elsevier.com/locate/jafrearsci Geochemistry of cretaceous fne-grained siliciclastic rocks from Upper Mundeck and Logbadjeck Formations, Douala sub-basin, SW Cameroon: Implications for weathering intensity, provenance, paleoclimate, redox condition, and tectonic setting Gabriel Ngueutchoua a,∗ , Armel Zacharie Ekoa Bessa a ,JohnTakenEyong a , David Demanou Zandjio b , Hadjidjatou Baba Djaoro a , Lionel Tchami Nfada a a Department of Earth Sciences, University of Yaoundé 1, P.O. Box 812, Yaoundé, Cameroon b Department of Earth Sciences, University of Dschang, P.O. Box 067, Dschang, Cameroon ARTICLEINFO Keywords: Rare earth elements Geochemistry Provenance Douala sub-basin Paleoclimate ABSTRACT The chemical composition of the Upper Mundeck Formation (UMF) and Logbadjeck Formation (LF) from the Douala sub-basin (Cameroon) has been investigated to determine their provenance, the infuence of the weathering,thepaleoclimate,andtheredoxconditionuponthesourcerocksignature,aswellastodecipherthe tectonicsettingofthesesediments.TheChemicalIndexofAlteration(CIA),PlagioclaseIndexofAlteration(PIA), andvariouspaleoweatheringproxiessuggestthattheserocksunderwenthighdegreeofchemicalweatheringin the source region. The intensity of weathering was higher for LF relative to UMF samples. The AeCNeK plot, coupledtothemineralogicalassemblage,dominatedbytheoccurrenceofillite,indicatesthatpost-depositional K-enrichmentsmayhaveafectedthebulkcompositionofthestudiedrocks.ThePostArcheanAustralianShale (PAAS)-normalized patterns of the investigated rocks show mostly moderate to high LREE/HREE ratios (up to 20.75) and negative to positive Eu anomalies, suggesting a provenance from felsic rock with negligible con- tribution of mafc components. The Rb/Sr ratio for UMF (0.43 ± 0.1) and LF (0.56 ± 0.31) suggests a gen- erally warm condition during their deposition. The V/Cr and U/Th ratios of UMF (3.29 ± 4.94 and 0.24 ± 0.10, respectively) and LF (1.67 ± 1.34 and 0.17 ± 0.03, respectively), and the authigenic uranium (AU) content of both formations indicate an oxic depositional environment. The Sr/Ba ratio of UMF (0.24 ± 0.21) and LF (0.33 ± 0.43) suggests an overall low salinity of the depositional environment. The tectonicdiscriminant-function-baseddiagramrevealedariftoracollisionalsettingforthestudiedrocks,which isinconsistentwiththegeneralgeologyoftheDoualasub-basin,revealingprobablythecomplexhistoryofthe source rock. 1. Introduction Geochemical composition of fne-grained clastic sediments is be- lieved to provide reliable clue to investigate on source rock character- istics(RoserandKorsch,1988; Armstrong-Altrinetal.,2004; Mortazavi etal.,2014; Dingetal.,2015; Fanetal.,2015; Madhavaraju,2015; Yu et al., 2016; Zou et al., 2016), weathering condition in source region (Selvaraj and Chen, 2006; Royetal.,2008; Gallalaetal.,2009) redox condition (Christopher and Elderfeld, 1990; Nath et al., 1997; Zou etal.,2015; Madhavarajuetal.,2016),paleoclimate(LermanandGat, 1989; JinandZhang,2002; Baietal.,2015),andtectonicsettingofa depositional milieu (Armstrong-Altrin and Verma, 2005; Sabaouetal., 2009; Armstrong-Altrin et al., 2015; Verma and Armstrong-Altrin, 2016). Fine-grained clastic sedimentary rocks are more useful to con- straint geochemical signatures than the coarse ones (Taylor and McLennan, 1985). The Cretaceous sedimentary successions of the Doualasub-basinhaveattractedtheattentionofthepetroleumindustry (ECL, 2001; Ntamak Nida et al., 2010). As a result, various studies, which produced an extensive amount of ofshore data, have been un- dertaken. Nevertheless many of these data have not been made avail- able to academic researchers, making these rock successions little de- tailedinliterature.Mostresearchers(Reyre, 1966; NjikeNgaha,1984; Regnoult, 1986; Benkhelil et al., 2002; Lawrence et al., 2002) con- ducted petrographic and structural studies to understand the https://doi.org/10.1016/j.jafrearsci.2019.02.021 Received22June2018;Receivedinrevisedform8February2019;Accepted12February2019 ∗ Corresponding author. E-mail address: ngueutchoua2@yahoo.fr (G. Ngueutchoua). Journal of African Earth Sciences 152 (2019) 215–236 Available online 18 February 2019 1464-343X/ © 2019 Elsevier Ltd. All rights reserved. T