James Kennett, an emeritus geologist at the University of California, Santa Barbara, stated that carbon spherules occur throughout the geological record but peak at the Younger Dryas boundary.
Notes on verification
UCSB press coverage and broader Younger Dryas impact hypothesis literature support the substance of the claim—carbon spherules form via multiple mechanisms and peak at the YDB layer—but no source directly quotes Kennett making this exact statement, so attribution is inferred rather than directly verified. [tier=silver indep_score=0.735 clusters=2 claim_tier=notable]
Sources
- Fungi, Feces Show Comet Didn't Kill Ice Age Mammals? (seed:history_and_archaeology)
- https://news.ucsb.edu/2013/013537/comprehensive-analysis-impact-spherules-supports-theory-cosmic-impact-12800-years-ago (corroboration)
- https://www.science.gov/topicpages/y/younger+dryas+impact (corroboration)