Synchroneity of the K-T oceanic mass extinction and meteorite impact; Blake Nose, western North Atlantic

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doi: 10.1130/0091-7613(1999)027<0419:SOTKTO>2.3.CO;2
Author(s): Norris, R. D.; Huber, B. T.; Self-Trail, J. M.
Author Affiliation(s): Primary:
Woods Hole Oceanographic Institution, Woods Hole, MA, United States
Smithsonian Institution, United States
U. S. Geological Survey, United States
Volume Title: Geology (Boulder)
Source: Geology (Boulder), 27(5), p.419-422. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613 CODEN: GLGYBA
Note: In English. 22 refs.; illus.
Summary: A 10-cm-thick layer of green spherules occurs precisely at the biostratigraphic boundary between the Cretaceous and Paleogene (K-T boundary) at Ocean Drilling Program Site 1049 (lat 30°08′N, long 76°06′W). The spherulitic layer contains abundant rock fragments (chalk, limestone, dolomite, chert, mica books, and schist) as well as shocked quartz, abundant large Cretaceous planktic foraminifera, and rounded clasts of clay as long as 4 mm interpreted as altered tektite glass probably derived from the Chicxulub impact structure. Most of the Cretaceous foraminifera present above the spherule layer are not survivors since small specimens are conspicuously rare compared to large individuals. Instead, the Cretaceous taxa in Paleocene sediments are thought to be reworked. The first Paleocene planktic foraminifera and calcareous nannofossil species are recorded immediately above the spherule bed, the upper part of which contains an iridium anomaly. Hence, deposition of the impact ejecta exactly coincided with the biostratigraphic K-T boundary and demonstrates that the impact event was synchronous with the evolutionary turnover in the oceans. These results are consistent with a reanalysis of the biostratigraphy of the K-T boundary stratotype, which argues that shallow-marine K-T boundary sections are not biostratigraphically more complete than deep-sea K-T boundary sites.
Year of Publication: 1999
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Algae; Atlantic Ocean; Biostratigraphy; Blake Nose; Blake Plateau; Cenozoic; Cretaceous; Ejecta; Foraminifera; Fragments; Impacts; Invertebrata; K-T boundary; Leg 171B; Lithostratigraphy; Lower Paleocene; Marine environment; Marine sediments; Mass extinctions; Mesozoic; Nannofossils; North Atlantic; ODP Site 1049; Ocean Drilling Program; Paleocene; Paleoecology; Paleogene; Planktonic taxa; Plantae; Protista; Reworking; Sediments; Spherulites; Stratigraphic boundary; Tektites; Tertiary; Upper Cretaceous
Coordinates: N300800 N300800 W0760600 W0760600
Record ID: 1999037068
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