K–T boundary spherules from Blake Nose (ODP Leg 171B) as a record of the Chicxulub ejecta deposits
F. Martínez-Ruiz, M. Ortega-Huertas, I. Palomo-Delgado, J. Smit, 2001. "K–T boundary spherules from Blake Nose (ODP Leg 171B) as a record of the Chicxulub ejecta deposits", Western North Atlantic Palaeogene and Cretaceous Palaeoceanography, Dick Kroon, R. D. Norris, A. Klaus
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The Cretaceous-Tertiary (K-T) boundary interval recovered by the ODP Leg 171 at Site 1049 (Blake Nose, NW Atlantic) contains a thick (9–17 cm) spherule bed marking the boundary. The spherules are mainly perfect spheres with a lesser proportion of oval spherules. They usually range from 100 to 1000 μm. This bed represent the diagenetically altered impact ejecta from Chicxulub and further supports this structure as the site of the K-T impact. Mineralogical and geochemical investigations indicate that impact-generated glass was altered to smectite. Transmission electron microscopy observations revealed in some spherules that smectite is forming from a Si-rich or Ca-rich material, which could suggest a precursor similar to Haitian glasses. The variable thickness and the presence of some Cretaceous planktonic foraminifera and clasts of Cretaceous chalk suggest reworking of the ejecta material. However, the spherule bed confirms that a large volume of the Chicxulub ejecta material reached the Blake Nose Plateau.
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Palaeogene and Cretaceous palaeoceanography has been the focus of intense international interest in the last few years, spurred by deep ocean drilling at Blake Nose in the North Atlantic as well as the need to use past climate change as input for modelling future climate change. This book brings together a number of review papers that describe ancient oceans and unique events in the Earth’s climatic history and evolution of biota. The papers show evidence of periods characterized by exceptional global warmth such as the Late Palaeocene Thermal Maximum and Cretaceous anoxic events. Geochemical records and modelling will make the reader aware that these periods were forced by greenhouse gases. This information is essential for understanding the response of the ocean—climate system to the current input of fossil fuels. In this sense, the book contributes to the understanding of fundamental aspects of Earth’s climate, the carbon cycle, and marine ecosystems. A number of papers describe massive mass wasting deposits resulting from the energy released by the bolide impact at the Cretaceous—Tertiary boundary as well as the geochemistry of the boundary itself. Additional papers cover aspects of cyclostratigraphy and biostratigraphy of Palaeogene and Cretaceous records.
This book will be of interest to a broad audience of Earth Scientists interested in Palaeogene—Cretaceous palaeoceanography, extreme climate modelling, Cretaceous—Tertiary boundary, Late Palaeocene Thermal Maximum, Cretaceous anoxic events, as well as those specifically interested in radiolarian, dinoflagellate and coccolithophorid stratigraphy.