Palynostratigraphy of Upper Mesozoic Outcrops near Anjiajia (Mahajanga Basin), and Manamana (Morondava Basin), and It’s Bearing on the Development of Cretaceous Angiosperm Floras in Madagascar

Abstract

The two outcrops were investigated palynologically. One outcrop is approximately a 17meter section near Anjiajia in the Mahajanga Basin and the second outcrop is approximately a 5meter section located in the Manamana massif-South Ankazoabo in the Morondava Basin. The section from Anjiajia was dominated by Cryptogrames (56%), Gymnosperms (29.5%) and a minor component of angiosperms (19%). Based on the sedimentology, composition of the palynoflora, the low percentage of angiosperms, and the occurrence of the dinoflagellate Litosphaeridium arundum at the Anjiajia sample is estimated to be Albian to Cenomanian in age. The section from Manamana is dominated by Cryptogrames (47%), Angiosperm (30.5%) and Gymnosperms (17.5 %). Based on the sedimentology, floral composition, the higher percentage of angiosperms relative to the Anjiajia sample, the occurrence of the Dinoflagellates Leberidocysta chlamydata and Odontochitina operculata and the location of the section beneath the Coniacian basalts in the Morondava basin, these data suggest a Turonian-Coniacian age for this sample. Based on these two Cretaceous palynofloras and a megafossil fossil flora from the Maevarano Formation (Santonian to Maastrichtian), which has only a few species of gymnosperms and is dominated by the Lower Cretaceous angiosperm Sapindopsis, it appears the southern hemisphere floras are lagging behind the northern hemisphere angiosperm floras in diversity and abundance.