New insights on the late Maastrichtian and Danian paleoenvironment from integrated magnetostratigraphy and multiproxy analyses of a shallow marine carbonate section, northeastern Brazil

The late Maastrichtian (Late Cretaceous) and Danian (early Paleogene) are punctuated by abrupt climatic perturbations modulated by global-scale events such as asteroid impacts (Chicxulub) and large igneous provinces (LIPs; e.g., Deccan Traps, North Atlantic Igneous Province). In this work, we analyzed magnetostratigraphy supplemented with planktic foraminifera biostratigraphy, environmental magnetic parameters, mineralogy, and major element chemistry from a well-defined Cretaceous-Paleogene (K/Pg) boundary section exposed in the Poty Quarry (a cement mine) of Paraíba Basin, NE Brazil, to establish the first age-depth model of the region, and to understand the impact of these events on equatorial shallow marine environments. To establish the age-depth model, 102 oriented samples were collected at ~15–20 cm intervals from ~11-m-thick carbonate strata covering the late Maastrichtian (Gramame Formation) and Danian (Maria Farinha Formation) and were demagnetized using alternating field (AF) demagnetization and thermal (Th) demagnetization methods to retrieve the characteristic remanent magnetizations (ChRM). Approximately 25% of specimens showed reliable paleomagnetic directions, which, combined with the planktic foraminifera biostratigraphic tie points, indicated that the exposed Poty Quarry section recorded magnetic chrons between C29r and C27n. Two new paraconformities (hiatuses) were also identified at ca. 65.2 Ma (duration = ~0.6 m.y.) and ca. 63.5 Ma (duration = ~0.8 m.y.), which correspond to the global Danian sea-level fall events PDa2 and PDa3, respectively. The low terrigenous flux and slow sedimentation (~0.09 cm/k.y.) in the late Maastrichtian is characterized by a highstand systems tract (HST) depositional environment, whereas higher sedimentation (~2.75 cm/k.y.) and maximum terrigenous flux between ca. 62.5 Ma and 62.3 Ma is characterized as regressive (prograding) depositional environment leading to shallowing of the Paraíba Basin toward the end of the Danian.