Two anomalies of platinum group elements above the Cretaceous-Tertiary boundary at Beloc, Haiti: Geochemical context and consequences for the impact scenario

A detailed geochemical investigation of an expanded Cretaceous-Tertiary (K-T) boundary section near Beloc (B3), Haiti, reveals a complex pattern of sedimentation of multiple origins as a result of erosional, biogenic, volcanic, and impact events. Carbonate-rich uppermost Maastrichtian sediments with high excess rates for Cu, Zn, and Sr (biogenic origin) indicate high productivity (δ¹³ C) and warm temperatures (δ¹⁸O). These sediments are overlain by Paleocene (early Danian zone P1a) spherule-rich clayey layers that indicate lower productivity, lower temperatures, and high input of glass and biogenic carbonate. Reworked Maastrichtian sediments are mixed with spherule-rich layers. This spherule-rich deposit is topped by a thin layer rich in Fe that also contains an Ir-dominated anomaly of platinum group elements (PGE) with an almost chondritic abundance pattern, which appears to be the result of a cosmic influx. Monotonous limestones above this interval reflect recovery to normal pelagic sedimentation, which is interrupted by a second PGE anomaly in an Fe-rich clayey layer in the middle part of zone P1a. All PGEs are enriched in this interval and the PGE pattern is basalt like, suggesting a volcanic source. Both PGE anomaly horizons coincide with productivity and temperature changes.