Cretaceous-Tertiary boundary at Blake Nose (Ocean Drilling Program Leg 171B); a record of the Chicxulub impact ejecta

Author(s): Martínez-Ruiz, Francisca; Ortega-Huertas, Miguel; Palomo, Inmaculada; Smit, Jan
Author Affiliation(s): Primary:
Instituto Andaluz de Ciencias de la Terra, Facultad de Ciencias, Granada, Spain
University of Missouri-Columbia, United States
Universidad de Granada, Spain
Vrije Universiteit de Boelelaan, Netherlands
Volume Title: Catastrophic events and mass extinctions; impacts and beyond
Volume Author(s): Koeberl, Christian, editor; MacLeod, Kenneth G.
Source: Catastrophic events and mass extinctions; impacts and beyond, edited by Christian Koeberl and Kenneth G. MacLeod. Special Paper - Geological Society of America, Vol.356, p.189-199. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0072-1077. ISBN: 1-8137-2356-6 CODEN: GSAPAZ
Note: In English. 153 refs.; illus., incl. 2 tables, sketch map
Summary: The Ocean Drilling Program (ODP) included as one of its Leg 171B objectives the recovery of a detailed record of the Cretaceous-Tertiary (K-T) events at Blake Nose (northwest Atlantic). This aim was successfully achieved with sections across the K-T boundary recovered at Sites 1049, 1050, and 1052, and a thick spherule bed recovered at ODP Site 1049. This spherule bed varies from 7 to 17 cm in thickness at the three different holes drilled at Site 1049, and occurs at the biostratigraphic boundary between the Cretaceous and the Paleocene. Mineralogical and geochemical analyses of the Blake Nose spherule bed reveal that it is mainly composed of smectite derived from the alteration of a precursor material, mostly glass. Also present in minor proportions are dolomite, quartz, zeolites, and trace amounts of rutile and some lithic fragments. Different types of spherules, dark green, pale yellow, and light green, that can be related to different precursors were observed in the Blake Nose spherule bed. Transmission electron microscope observations showed that smectite directly replaced the original material and that dark green spherules originated from a Si-rich precursor, whereas pale yellow spherules originated from a more Ca-rich precursor. The chemical composition of the spherule-bed material at Blake Nose shows little evidence for a significant extraterrestrial contribution, suggesting that the spherule-bed material was mainly derived from the alteration of target-rock-derived material from Chicxulub crater. In addition, rare earth element C1-normalized patterns also suggest that this material was derived from upper crustal rocks.
Year of Publication: 2002
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Alteration; Atlantic Ocean; Atomic absorption spectra; Biostratigraphy; Blake Nose; Blake Plateau; Cenozoic; Chemical composition; Chicxulub Crater; Cores; Cretaceous; Diagenesis; Ejecta; Impacts; K-T boundary; Leg 171B; Lower Paleocene; Mass spectra; Mesozoic; Metals; Mineral composition; North Atlantic; ODP Site 1049; ODP Site 1050; ODP Site 1052; Ocean Drilling Program; Paleocene; Paleogene; Rare earths; SEM data; Spectra; Spherules; Stratigraphic boundary; TEM data; Tertiary; Upper Cretaceous; X-ray diffraction data
Coordinates: N093943 N093943 W0861045 W0861045
N300600 N300600 W0761406 W0761406
N295705 N295705 W0763736 W0763736
Record ID: 2002073209
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