"Younger Dryas Impact Study”- Summer 2008
The events precipitating the dramatic, millennial long climatic cooling known as the Younger Dryas, that occurred approximately 13,000 years ago remain a mystery. Recent evidence suggests an extraterrestrial impact on the Laurentide ice sheet may have provided the trigger for a massive influx of fresh glacial melt water theorized to have flooded the North Atlantic and shut down the Thermohaline circulation that moderates climate in the northern hemisphere.The apparent absence of an easily identified impact crater has focused the search for evidence of an impact on a search for extraterrestrial markers embedded in the Earth’s sedimentary record.
Association of an impact with coincident reduction in the numbers of megafauna species and human population of North America has suggested a strategy for the search for evidence of the impact. If an impact is responsible for initiating the onset of the Younger Dryas, the ultimate disappearance of megafauna species and the decline in human population, then the evidence should lie at the sedimentary boundary (YDB) separating the Younger Dryas from the preceding Bolling-Allerod at a depth corresponding to 12,900 years before present.
Some of these evidential markers (magnetic grains and spherules, charcoal, and glass-like carbon) was relatively easy to extract and identify while others (nanodiamonds and fullerenes) required great care, expensive instrumentation and considerable training. Fortunately, the vessels (carbon spherules) containing the more challenging markers were identified and extracted during the soil processing for magnetic spherules and charcoal. The research project also included an investigation of local paleo-lake depressions known to harbor impact markers and whose stratigraphy could have revealed a clearer understanding of the processes that shaped the coastal topography during the Younger Dryas. The research was carried out using a combination of Ground Penetrating RADAR (GPR) and sample coring to probe the subsurface deposits of selected depressions.