Sequence and cyclostratigraphic analysis of Paleocene carbonate sediments in the Chicxulub impact crater: Implications for sea level change and climate dynamics

The early Paleogene represents a greenhouse Earth experiencing large-scale global environmental changes after the Cretaceous-Paleogene extinction. Understanding climate and ocean dynamics during this recovery phase is challenging due to the scarcity of continuous, carbonate-rich sedimentary records. The Paleocene interval of International Ocean Discovery Program−International Continental Scientific Drilling Program (IODP-ICDP) Site M0077 from within the Chicxulub crater provides such an archive. Sequence and cyclostratigraphic analyses reveal condensed and rhythmic bedding, transitioning between marl or argillaceous wackestone and foraminiferal packstones. These 5−33-cm-thick cycles document low-amplitude sea-level changes or local environmental shifts in the Chicxulub basin associated with sea level. The cycles exhibit retrogradational, progradational, or aggradational facies stacking patterns, indicative of transgressive, highstand, and shelf margin systems tracts. Progradational packages align with global sea-level events, suggesting a eustatic driver. Cyclostratigraphy on the sediments’ color reflectance reveals 10 cm and 20 cm periodicities, interpreted as 41 k.y. obliquity and 100 k.y. eccentricity signatures. These climate-driven cycles resemble Paleogene hyperthermals, intensifying the hydrologic cycle and erosion of fine-grained siliciclastic sediments in the Chicxulub hinterland. Thereby, hyperthermals correspond to marl or argillaceous wackestone facies. Moreover, sequence boundaries tend to correspond to minima in the 1.2 m.y. obliquity modulation cycle. This longer-term astronomical control on sea level and climate offers insights into potential drivers of eustatic sea-level change in the Paleocene greenhouse world. The phase relationship between sea level and the 1.2 m.y. obliquity cycle indicates increased water storage in continental reservoirs during periods of astronomically suppressed seasonality (i.e., 1.2 m.y. obliquity minima). Thus, the carbonate sedimentological study of the Paleocene Chicxulub sequences provides unique insights into both local and global environmental dynamics.