It is widely recognized that a significant negative excursion in carbon isotopic (δ13C) differences between planktic and benthic foraminiferal tests occurred at the Cretaceous-Tertiary (K-T) boundary. We applied parametric and nonparametric breakpoint tests and statistical comparisons of different recovery models to assess the timing and pattern of recovery from this negative excursion at South Atlantic Deep Sea Drilling Project (DSDP) Site 528 and equatorial Pacific DSDP Site 577. Our results indicate a two-stage recovery with an initial recovery to an intermediate state of planktic-to-benthic δ13C differences followed by a discontinuous shift to a final state with planktic-to-benthic δ13C differences similar to preextinction values. The final discontinuous shift in both the Pacific and Atlantic Ocean sites occurred several million years after the K-T collapse of planktic-to-benthic δ13C differences. Both the first and second stages of recovery are best described by damped exponential relaxations. The pattern and timing of this carbon cycle recovery may have been contingent on the occurrence of key biological events.
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