Supports· strongYDIH-E014
Haynes 2008: the black mats documented — as wetland deposits
- what the source states
- A survey of terminal-Pleistocene sites documented widespread dark, organic-rich "black mat" horizons overlying the Rancholabrean surface — frequently draping the last in-place megafaunal remains and Clovis occupations — attributing the mats to elevated water tables, spring discharge, and organic accumulation during the moist Younger Dryas interval.
- what we infer
- Supports the observation claim precisely because it is the careful version of it: the mats are real, striking, and stratigraphically associated with the transition — and their documenter's own account of what they are (wetland facies) is the strongest reason they cannot serve as an impact marker.
- limitations
- Black mats occur at many other times and places; the association with the YD onset is environmental, not event-diagnostic.