High-resolution sequence stratigraphy of Upper Jurassic lacustrine cycles in the Parnaíba Basin, Brazil: Unraveling basin evolution through climate and thermal subsidence

Palaeolakes of the Late Jurassic, in West Gondwana, were critically shaped by thermal subsidence, driven by isostatic adjustment, isotherm downgrading, and the cooling of mafic magma associated with the Central Atlantic Magmatic Province (CAMP) around 201 Ma. These key processes are recorded in the Pastos Bons Formation, located within the Parnaíba Basin in northeastern Brazil. Although this sedimentary succession has recently been examined from a palaeoenvironmental perspective, a significant gap remains in characterizing its stacking patterns through the lens of high-resolution sequence stratigraphy (HRSS). Therefore, there remains a lack of clarity regarding the interplay between climatic and thermal subsidence and its influence on sedimentation and lake level fluctuations. Hence, we identified twenty sedimentary facies, grouped into six facies associations: central lake (FA1), hyperpycnal littoral delta (FA2), lakeshore (FA3), alluvial fan (FA4), fluvial (FA5), and delta front (FA6). The HRSS framework reveals three medium-frequency sequences, representing clusters of high-frequency T-R (transgressive-regressive) sequences, controlled by long-term climatic changes: sequence-1 (Seq-1), sequence-2 (Seq-2), and sequence-3 (Seq-3). Seq-1 and Seq-2 exhibit a higher proportion of transgressive system tract (TST) than regressive system tract (RST), and they demonstrate dramatic fluctuations in lake level. In contrast, Seq-3 shows a predominance of the regressive systems tract (RST) over the transgressive systems tract (TST), reflecting greater stability in lake level. The medium-frequency framework reveals that the Pastos Bons Formation is characterized by a balanced-fill lacustrine basin (Seq-1 and Seq-2) overlaid by an overfilled lacustrine basin (Seq-3). The low-frequency chronostratigraphic framework, composed of clusters of medium-frequency T-R sequences (seismic scale), indicates that post-CAMP thermal subsidence presents a primary control on the configuration, size, shape, and accommodation potential of the lacustrine basin. Post-CAMP subsidence along the Equatorial Atlantic margins during the Late Jurassic period played a key role in shaping the palaeogeography of West Gondwana, promoting the development of lacustrine basins.