Detrital apatite fission-track ages in Middle Jurassic strata at the rifted margin of W Madagascar—indicator for a protracted resedimentation history

Abstract

The combination of litho- and biostratigraphic data, detrital apatite fission-track (FT) ages, and palaeocurrent data from Jurassic sedimentary successions in the southern Morondava Basin (SW Madagascar) suggests a resedimentation of the detrital material. Detrital apatite FT ages of Middle Jurassic sedimentary rocks range between 428 ± 31 Ma to 233 ± 18 Ma. All apatite FT ages are older than their stratigraphic ages and become younger from top to the bottom of a Middle Jurassic profile. Such an apatite FT age distribution can be produced by a double inversion of the stratigraphic succession. Since the Late Carboniferous crustal extension between East Africa and Madagascar occurred. The sampled material was initially deposited prior to the Middle Jurassic, most probably during the Karoo Rifting (Latest Carboniferous–Late Triassic). Subsequently, resedimentation occurred during a second sedimentation cycle, which was probably connected to rift jump during the Jurassic Gondwana breakup and passive margin development between East Africa and Madagascar. This study demonstrates that under certain temperature constraints detrital apatite FT age distributions combined with litho- and biostratigraphic data can be used to verify sedimentation–resedimentation events.