Journal article
New Jersey, a most habitable place during an asteroid strike; shocked quartz and iridium spike co-occur below a Maastrichtian mollusk community on the NJ coastal plain
Abstracts with programs - Geological Society of America, Vol.47(7)
Geological Society of America, 2015 annual meeting & exposition (2015)
2015
Abstract
Previous studies have identified K/Pg boundary sites on the New Jersey Coastal Plain. The Agony Creek section (30-45 m paleodepth) in the Manasquan River Basin is of particular interest because there is a discrepancy in the biotic and physical indicators of the impact. Here, an Ir anomaly is located at the base of a Maastrichtian assemblage, the approximately 20 cm thick "Pinna Layer", which includes ammonites. Another impact indicator is identified at the base of the Pinna Layer: Pyrite framboids enriched in Ni and Co up to 100x above background. We find similar framboids and shocked quartz with planar deformation features (PDFs) at Crosswicks Creek (50-75 m paleodepth), coincident with an Ir spike and the biostratigraphic boundary. The occurrence of quartz grains with PDFs below or above the Pinna Layer at Agony Creek would resolve conflicting evidence for whether this fauna survived the impact. Samples were obtained from exposed stream banks at Agony Creek, collected at 1 cm intervals from the base of the Ir anomaly upward ( approximately 24 cm) to the base of the Hornerstown Formation (earliest Danian). Samples were leached in HCl to remove iron staining and sieved to isolate grains between 62-150 mu m. Quartz grains were magnetically separated from glauconite and observed under a petrographic microscope to determine PDFs. Universal stage measurements confirm that the planar features observed in quartz from the Ir-rich layer are PDFs related to the Chicxulub impact. Shocked quartz grains occur at the same horizon as the Ir anomaly but not above it. This coincidence suggests that the Ir (and Ni, Co) did not diffuse downward after deposition. The overlying Pinna Layer fauna are in life position and are not reworked. Our new findings therefore suggest that this community may have flourished for a brief time (10's of years) after the Chicxulub impact.
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Details
- Title
- New Jersey, a most habitable place during an asteroid strike; shocked quartz and iridium spike co-occur below a Maastrichtian mollusk community on the NJ coastal plain
- Creators
- Denton S. Ebel - American Museum of Natural History, Department of Earth and Planetary Sciences New York, NY USA United StatesShaun MahmoodSteven J. JaretJohn N. BigolskiRachel J. AldorotyJocelyn A. SessaNeil H. LandmanAnonymous
- Publication Details
- Abstracts with programs - Geological Society of America, Vol.47(7)
- Conference
- Geological Society of America, 2015 annual meeting & exposition (2015)
- Publisher
- Geological Society of America (GSA)
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Biodiversity, Earth, and Environmental Science (BEES)
- Identifiers
- 991021013185204721