Multiple Ir anomalies in uppermost Triassic to Jurassic-age strata of the Blomidon Formation, Fundy basin, eastern Canada

作者：Tanner Lawrence H^*; Kyte Frank T; Walker Ann E

来源：Earth and Planetary Science Letters, 2008, 274(1-2): 103-111.

DOI：10.1016/j.epsl.2008.07.013

• iridium
• trace elements
• Triassic
• Jurassic
• CAMP

A detailed Profile of IF concentrations in continental strata of the Blomidon Formation ostensibly spanning the Triassic-Jurassic boundary confirms the existence of multiple anomalies, with a peak IF concentration of 450 pg/g. The total amount of IF deposited exceeds 4 ng/cm(2), a value that requires an external source other than typical terrestrial sediment. Of the 10 other elements measure, only Zn and organic carbon are correlated to IF. The organic carbon appears to be concentrated in mm-thick kerogenous laminae in greenish-grey to dark grey sediment layers that also host the IF anomalies. The stratigraphic distribution of IF and probably Zn appears to be controlled largely by redox boundaries conditions, with IF probably forming organo-metallic complexes. We find no specific geochemical or sedimentological evidence for an extraterriestrial source for this enrichment, although we cannot exclude an impact origin. However, the close spatial and temporal relationship of the IF anomalies in the Fundy and Newark basins to the basalts of the Central Atlantic Magmatic Province suggests alternative working hypotheses. Potentially, the volcanic rocks sourced the IF through post-eruptive fluid mobilization into the surrounding sediments. Conversely, mantle outgassing and aerosol deposition during early stages of the eruptions may have been the source for the IF anomalies. At this time, the data are insufficient to eliminate any of these hypotheses conclusively.

• 出版日期2008-9-30