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Continuous, expanded, and undisturbed Cretaceous/Tertiary boundary sequences were recovered in three holes drilled at Deep Sea Drilling Project Site 577 (32°26.51'N, 157°43.40'E) on Shatsky Rise. The Cretaceous/Tertiary boundary lies at a sub-bottom depth of approximately 109.6 m in a white calcareous ooze. It was identified biostratigraphically within the magnetic C-29R subchron using nannofossils and is characterized by an iridium anomaly of 61 ng/cm 2 and a sharp 1% decrease in 13 C. Limited organic geochemical samples suggest that molecular stratigraphy cannot be applied definitively across the boundary.

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