Biotic, paleoceanographic, and stratigraphic changes across the Cretaceous/Paleogene boundary

• Main Author: Esmeray Senlet, Selen
• Format: Text
• Language: unknown
• Published: No Publisher Supplied 2015
• Subjects: Pacific; Planktonic foraminifera
• Online Access: https://dx.doi.org/10.7282/t3rx9dsx; https://rucore.libraries.rutgers.edu/rutgers-lib/46335/

My dissertation investigates the sea-level changes, large perturbations in the oceanic carbon cycle, and enrichments and distribution of iridium (Ir) across the Cretaceous/Paleogene (K/Pg) boundary (~66 Ma). Biostratigraphic, lithofacies, and sequence stratigraphic analyses of the Haymana (Turkey) and Campo Pit (New Jersey, USA) sections show that the K/Pg boundary occurred during a transgressive systems tract, below a maximum flooding surface. Similar sea-level trends recorded in European and North African sections suggest that the K/Pg event occurred during a global sea-level rise. Previous studies showed that the K/Pg mass extinction was associated with drastic perturbations in the oceanic carbon cycle, including a collapse in the carbon isotopic (δ13C) gradient between planktonic and benthic foraminifera and a drop in bulk carbonate δ13C values in deep-sea sites. The New Jersey paleoshelf recorded a ~2.5‰ δ13C decrease in bulk carbonate, a ~0.8‰ δ13C decrease in organic carbon, a collapse of the vertical δ13C difference between planktonic and benthic foraminifera, and a significant decrease in organic carbon mass accumulation rates. A ~1.0‰ water column δ13C gradient in planktonic foraminifera and a ~0.75‰ cross-shelf δ13C gradient in benthic foraminifera indicates the presence of primary productivity in the early Danian. Comparison of deep Atlantic and Pacific sites shows a reduction in interbasinal δ13C differences, most consistent with reduced export productivity. Anomalous Ir concentrations occur at the K/Pg boundary in New Jersey, though the maximum Ir concentrations and the thickness of the sediments over which Ir is spread is highly variable. The shape of the Ir profiles and the maximum concentrations of Ir measured in the cores appear to be determined primarily by sedimentary and geochemical processes, especially bioturbation as also shown by a Lagrangian particle-tracking model of sediment mixing. The depth-integrated Ir inventory is very similar in the majority of the cores, indicating that the total Ir delivery at the time of the K/Pg event was spatially homogenous over this region. This provides additional evidence for redistribution of Ir after original deposition and shows that low to moderate Ir concentrations (~0.1 – 0.5 ppb) can be the product of the same Ir delivery as nearby higher peaks (~2.4 ppb).