Pb isotopic tracers of the Cretaceous-Tertiary extinction event

Journal Article · Wed Nov 01 00:00:00 EST 1989 · Geophysical Research Letters (American Geophysical Union); (USA)

DOI:https://doi.org/10.1029/GL016i011p01301· OSTI ID:5667961

Galer, S J.G.; Macdougall, J D; Erickson, III, D J ^[1]

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1. Scripps Institution of Oceanography, La Jolla, CA (USA)

The global excess of Ir in sediments at the Cretaceous-Tertiary (K-T) boundary has been attributed to either a meteorite impact or enhanced volcanism (e.g. Decan Traps). The isotropic composition of Pb associated with this Ir provides a test of these hypotheses because meteoritic Pb is isotopically quite distinct from Pb of volcanic or continental origin. Pb abundances and isotopic compositions of pelagic oozes from DSDP Site 577A (Shatsky Rise, NW Pacific) measured in this study show little change over the deposition interval of Ir-rich sediment ({approximately}10 cm). However, a Pb enriched layer with a more radiogenic isotopic composition is found in the basal {approximately}0.5 cm of the Tertiary. These observations appear to preclude the Ir excess in these sediments originating as impact fallout from a stony meteorite although an iron meteorite impactor cannot be excluded. Any Pb flux accompanying Ir in volcanogenic aerosols from the Decan Traps should be considerable. However, the boundary Pb spike does not isotopically resemble known Deccan Trap lavas. There is isotopic overlap with coal ash although the lack of correlation between soot and Pb abundance precludes any simple relationship between the two. Overall, any wind pattern changes following the K-T event were apparently short-lived as neither airborne sources of Pb nor their magnitude to the then central Pacific were affected while Ir enriched sediments were being laid down.

• OSTI ID: 5667961
• Journal Information: Geophysical Research Letters (American Geophysical Union); (USA), Vol. 16:11; ISSN 0094-8276
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CRETACEOUS PERIOD
BOUNDARY CONDITIONS
LEAD ISOTOPES
ISOTOPE RATIO
TERTIARY PERIOD
ASHES
COAL
DEPOSITION
ENRICHMENT
GEOLOGIC HISTORY
IRIDIUM
LAVA
METEORITES
ORIGIN
PACIFIC OCEAN
VOLCANISM
WIND
CARBONACEOUS MATERIALS
CENOZOIC ERA
ELEMENTS
ENERGY SOURCES
FOSSIL FUELS
FUELS
GEOLOGIC AGES
ISOTOPES
MATERIALS
MESOZOIC ERA
METALS
PLATINUM METALS
RESIDUES
SEAS
SURFACE WATERS
TRANSITION ELEMENTS
580000* - Geosciences