Chicxulub impact ejecta at the Cretaceous-Paleogene (K-Pg) boundary from ODP Leg 207, tropical western North Atlantic; implications for ejecta composition and dispersal

Author(s): Schulte, Peter; Deutsch, Alexander; Kontny, Agnes; Krumm, Stefan; Joachimski, Michael
Author Affiliation(s): Primary:
Universität Erlangen, Institut für Geologie-Mineralogie, Erlangen, Federal Republic of Germany
Other:
Universität Münster, Federal Republic of Germany
Universität Karlsruhe, Federal Republic of Germany
Volume Title: Geological Society of America, 2007 annual meeting
Source: Abstracts with Programs - Geological Society of America, 39(6), p.372; Geological Society of America, 2007 annual meeting, Denver, CO, Oct. 28-31, 2007. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7592 CODEN: GAAPBC
Note: In English
Summary: The ODP Leg 207 from the Demerara Rise, tropical western North Atlantic, has recovered an expanded and stratigraphically complete Cretaceous-Paleogene (K-Pg) sedimentary record that also includes a well-developed Chicxulub ejecta deposit. Therefore, ODP Leg 207 provides insights into the Maastrichtian-Danian deepwater record from low latitudes and ejecta deposition possibly in an upward direction from an oblique (>45°) Chicxulub impact (Morgan et al., 2006, EPSL). We have conducted a high-resolution mineralogical, isotope geochemical, and rock magnetic study to characterize the Chicxulub ejecta deposit and reveal subsequent environmental changes. The single 1.5-2 cm Chicxulub ejecta horizon is composed of a normally graded layer of spherules that decrease in diameter from ∼2 to ∼0.25 mm. The upper third part of the of spherule layer also includes "round" dolomite clasts and accretionary carbonate clasts as well as shocked quartz and feldspar grains. Spherules are massive, hollow, or vesicle-rich, and some show in situ collapse. The graded nature, the complex composition of the ejecta, and the, in part, good preservation of delicate spherule textures suggests an origin as primary air-fall deposit. Spherules are altered to well-crystallized Na,-Ca-rich smectite and comprise internal globules, schlieren and lath-shaped crystals with a distinct Fe and Mg enrichment. These textures are indicative of silicate-silicate "liquid immiscibility" and quenching from a melt, suggesting a primary origin. Similar Fe-Mg-enrichment has been observed in Chicxulub spherules from Mexico and Texas. The occurrence of the characteristic Chicxulub-derived spherule layer at the base of Biozone P0 in conjunction with the mass extinction of planktonic foraminifera, the strong Iridium-anomaly (MacLeod et al., 2007, GSA Bulletin, v. 119, 101-115) and the sharp negative δ13C anomaly strengthens the genetic link between the Chicxulub impact and the K-Pg boundary clay.
Year of Publication: 2007
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Alkaline earth metals; Atlantic Ocean; Biozones; C-13/C-12; Carbon; Cenozoic; Characterization; Chemical composition; Chicxulub Crater; Composition; Cretaceous; Danian; Demerara Rise; Ejecta; Equatorial Atlantic; Foraminifera; Geochemical anomalies; High-resolution methods; Immiscibility; In situ; Invertebrata; Iron; Isotope ratios; Isotopes; K-T boundary; Leg 207; Lower Paleocene; Maestrichtian; Magnesium; Mass extinctions; Melts; Mesozoic; Metals; Microfossils; Mineral composition; North Atlantic; Northwest Atlantic; Ocean Drilling Program; Paleocene; Paleogene; Paleomagnetism; Planktonic taxa; Preservation; Protista; Senonian; Spherules; Stable isotopes; Stratigraphic boundary; Tertiary; Textures; Upper Cretaceous; West Atlantic
Coordinates: N090200 N092800 W0541100 W0544400
Record ID: 2009078532
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