I’m looking forward to my 2nd year defending a poster at the Fall AGU in San Francisco., December 14-18, 2009. I put the other presentations for our 2009 session here : “Younger Dryas Boundary: Extraterrestrial Impact or Not? (Caution: A Firefox browser will probably display this page incorrectly).
I’ll put the finished poster up as soon as I can.
Here is the PBS-NOVA episode this spring on our theory.
Nanodiamonds and Carbon Spherules from Tunguska, the K/T Boundary, and the Younger Dryas Boundary Layer
SESSION: Younger Dryas Boundary: Extraterrestrial Impact or Not?
AUTHORS (FIRST NAME, LAST NAME): James H Wittke1, Ted E Bunch1, Allen West2, James Kennett3, Douglas J
Kennett4, George A Howard5
1. Dept. of Geology, Northern Arizona Univ., Flagstaff, AZ, USA.
2. GeoScience Consulting, Dewey, AZ, USA.
3. Dept. of Earth Science and Marine Science Institute, Univ. of California, Santa Barbara, CA, USA.
4. Dept. of Anthropology, Univ. of Oregon, Eugene, OR, USA.
5. Restoration Systems, LLC, Raleigh, NC, USA.
Body: More than a dozen markers, including nanodiamonds (NDs) and carbon spherules (CS), occur in a sedimentary layer marking the onset of the Younger Dryas (YD) cooling episode at ~12.9 ka. This boundary layer, called the YDB, has been found at nearly forty locations across North America, Europe, and Asia, although not allmarkers are present at any given site. Firestone et al. (2007) and Kennett et al. (2008, 2009) proposed that these markers resulted from a cosmic impact/airburst and impact-related biomass burning. Here we report features common to the YDB event, the Cretaceous-Tertiary (K/T) impact, and the Tunguska airburst of 1908. In sediments attributed to each event, we and other researchers have recovered NDs either inside or closely associated with CS, which appear to be the hightemperature
by-products of biomass burning. CS range in diameter from about 500 nanometers to 4 millimeters with a mean of ~100 microns, and they typically contain NDs, including lonsdaleite (hexagonal diamonds), in the interior matrix and in the crust. To date, CS and NDs have been found in the K/T layer in the United States, Spain, and New Zealand. Similarly, CS and NDs have been found in the YDB layer in the United States, Canada, United Kingdom, Belgium, the Netherlands, Germany, and France. Thus far, every site examined contains NDs and/or CS in the K/T and YDB layers; conversely, we have yet to detect CS associated with NDs in any non-YDB sediments tested. Five allotropes of NDs have been identified in association with CS: cubic diamonds, lonsdaleite, n-diamonds, p-diamonds, and i-carbon, which are differentiated by slight variations in their crystalline structure. All allotropes have been identified using scanning electron microscopy (SEM), high-resolution electron microscopy (HREM), and transmission electron microscopy (TEM) with confirmation by selected area diffraction (SAED). Lonsdaleite is found on Earth only in three instances: (1) in the laboratory, where it is produced by shock synthesis under a high-temperature-high-pressure regime (~1000°C to 1700°C at 15 GPa) or by carbon vapor deposition (CVD) under a very-high-temperature-lowpressure regime (~13,000°C at 300 Torr) (Maruyama et al., 1993); (2) after arrival on Earth inside extraterrestrial material; and (3) as a result of high-temperature cosmic impact/airbursts. Lonsdaleite associated with CS has been found in sediments only at the K/T, the YDB, and Tunguska, consistent with the hypothesis that all three events have cosmic origins, although the nature of the impactors may have been different.
KEYWORDS:  GLOBAL CHANGE / Abrupt/rapid climate change,  MINERALOGY AND PETROLOGY /
Meteorite mineralogy and petrology,  PLANETARY SCIENCES: COMETS AND SMALL BODIES / Impact
phenomena,  PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS / Meteorites and tektites.
Previously Presented Material: 20% presented at AGU, 2008