A5062971783- Geology and Paleoclimatology Research
- Paleontology and Stratigraphy of Fossils
- Geological and Geochemical Analysis
- Astro and Planetary Science
- Archaeology and ancient environmental studies
- Planetary Science and Exploration
- Hydrocarbon exploration and reservoir analysis
- Isotope Analysis in Ecology
- Methane Hydrates and Related Phenomena
- Geochemistry and Elemental Analysis
- Archaeology and Historical Studies
- Geochemistry and Geologic Mapping
- Fire effects on ecosystems
- Fullerene Chemistry and Applications
- Pleistocene-Era Hominins and Archaeology
- Atmospheric and Environmental Gas Dynamics
- Ion-surface interactions and analysis
- Marine and environmental studies
- Electron and X-Ray Spectroscopy Techniques
- Astronomical and nuclear sciences
- Geological formations and processes
- High-pressure geophysics and materials
- Chemical Reaction Mechanisms
- Polar Research and Ecology
- Aluminum Alloys Composites Properties
DePaul University
2012-2025
National Institute for Materials Science
2009
University of Oregon
2009
University of California, Santa Barbara
2009
Center for Environmental Health
2009
University of California, Los Angeles
2009
Illinois Wesleyan University
1994-1998
University of Chicago
1985-1993
Fermi National Accelerator Laboratory
1985-1993
Franklin & Marshall College
1983-1985
A carbon-rich black layer, dating to ≈12.9 ka, has been previously identified at ≈50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones extinct Pleistocene megafauna, along Clovis tool assemblages, occur below this layer but not within or above it. Causes for extinctions, YD cooling, termination culture have long controversial. In paper, we provide evidence an extraterrestrial (ET) impact event ≅12.9 which...
Clay samples from three Cretaceous-Tertiary boundary sites contain 0.36 to 0.58 percent graphitic carbon, mainly as fluffy aggregates of 0.1 0.5 micrometers-apparently a worldwide layer soot. It may have been produced by wildfires triggered giant meteorite. This corresponding global abundance 0.021 +/- 0.006 gram per square centimeter, could greatly enhanced the darkening and cooling earth rock dust, which has suggested cause extinctions. The surprisingly large amount soot (10 present...
We report abundant nanodiamonds in sediments dating to 12.9 +/- 0.1 thousand calendar years before the present at multiple locations across North America. Selected area electron diffraction patterns reveal two diamond allotropes this boundary layer but not above or below that interval. Cubic diamonds form under high temperature-pressure regimes, and n-diamonds also require extraordinary conditions, well outside range of Earth's typical surficial processes common cosmic impacts. N-diamond...
We report the discovery in Lake Cuitzeo central Mexico of a black, carbon-rich, lacustrine layer, containing nanodiamonds, microspherules, and other unusual materials that date to early Younger Dryas are interpreted result from an extraterrestrial impact. These proxies were found 27-m-long core as part interdisciplinary effort extract paleoclimate record back through previous interglacial. Our attention focused on anomalous, 10-cm-thick, carbon-rich layer at depth 2.8 m dates 12.9 ka...
The Younger Dryas impact hypothesis posits that a cosmic across much of the Northern Hemisphere deposited boundary (YDB) layer, containing peak abundances in variable assemblage proxies, including magnetic and glassy impact-related spherules, high-temperature minerals melt glass, nanodiamonds, carbon aciniform carbon, platinum, osmium. Bayesian chronological modeling was applied to 354 dates from 23 stratigraphic sections 12 countries on four continents establish modeled YDB age range for...
The Younger Dryas boundary (YDB) cosmic-impact hypothesis is based on considerable evidence that Earth collided with fragments of a disintegrating ≥100-km-diameter comet, the remnants which persist within inner solar system ∼12,800 y later. Evidence suggests YDB cosmic impact triggered an "impact winter" and subsequent (YD) climate episode, biomass burning, late Pleistocene megafaunal extinctions, human cultural shifts population declines. deposited anomalously high concentrations platinum...
Part 1 of this study investigated evidence biomass burning in global ice records, and here we continue to test the hypothesis that an impact event at Younger Dryas boundary (YDB) caused anomalously intense episode ∼12.8 ka on a multicontinental scale (North South America, Europe, Asia). Quantitative analyses charcoal soot records from 152 lakes, marine cores, terrestrial sequences reveal major peak (YD) onset appears be highest during latest Quaternary. For Cretaceous-Tertiary (K-Pg) event,...
High-pressure liquid chromatography with ultraviolet-visible spectral analysis of toluene extracts samples from two Cretaceous-Tertiary (K-T) boundary sites in New Zealand has revealed the presence C(60) at concentrations 0.1 to 0.2 parts per million associated soot. This technique verified also that fullerenes are produced similar amounts soots common flames under ambient atmospheric conditions. Therefore, K-T layer may have originated extensive wildfires were cataclysmic impact event...
The long-standing controversy regarding the late Pleistocene megafaunal extinctions in North America has been invigorated by a hypothesis implicating cosmic impact at Allerød-Younger Dryas boundary or YDB (approximately 12,900 +/- 100 cal BP 10,900 (14)C years). Abrupt ecosystem disruption caused this event may have triggered extinctions, along with reductions other animal populations, including humans. remains controversial due to absence of shocked minerals, tektites, and craters. Here, we...
Abstract The Younger Dryas (YD) impact hypothesis posits that fragments of a large, disintegrating asteroid/comet struck North America, South Europe, and western Asia ~12,800 years ago. Multiple airbursts/impacts produced the YD boundary layer (YDB), depositing peak concentrations platinum, high-temperature spherules, meltglass, nanodiamonds, forming an isochronous datum at >50 sites across ~50 million km² Earth’s surface. This proposed event triggered extensive biomass burning, brief...
Abstract Net calcium flux (JCa) from bone in vitro is pH dependent. When falls below 7.40, through a reduction [HCO3−], there both physicochemical and cell-mediated JCa. To characterize the effect of acidosis on we inhibited bone-resorbing cells (osteoclasts) with specific inhibitor calcitonin studied JCa ion composition using an analytic high-resolution scanning microprobe. Neonatal mouse calvariae were cultured for 48 h physiologically neutral medium (Ntl, = 7.41, [HCO3−] 25 nM) or that...
A major cosmic-impact event has been proposed at the onset of Younger Dryas (YD) cooling episode ≈12,800 ± 150 years before present, forming YD Boundary (YDB) layer, distributed over >50 million km2 on four continents. In 24 dated stratigraphic sections in 10 countries Northern Hemisphere, YDB layer contains a clearly defined abundance peak nanodiamonds (NDs), proxy. Observed ND polytypes include cubic diamonds, lonsdaleite-like crystals, and diamond-like carbon nanoparticles, called...
We present evidence that in ~ 1650 BCE (~ 3600 years ago), a cosmic airburst destroyed Tall el-Hammam, Middle-Bronze-Age city the southern Jordan Valley northeast of Dead Sea. The proposed was larger than 1908 explosion over Tunguska, Russia, where 50-m-wide bolide detonated with 1000× more energy Hiroshima atomic bomb. A city-wide 1.5-m-thick carbon-and-ash-rich destruction layer contains peak concentrations shocked quartz 5-10 GPa); melted pottery and mudbricks; diamond-like carbon; soot;...
At Abu Hureyra, a well-studied archeological site in Syria, the onset boundary of Younger Dryas climatic episode ~12,800 years ago has previously been proposed to contain evidence supporting near-surface cosmic airburst impact that generated temperatures >2000°C. Here, we present wide range potential impact-related proxies representing catastrophic effects this destroyed village. These include nanodiamonds (cubic diamonds, n -diamonds, i -carbon, and lonsdaleite-like crystals);...
Abstract We report the discovery in Greenland ice sheet of a discrete layer free nanodiamonds (NDs) very high abundances, implying most likely either an unprecedented influx extraterrestrial (ET) material or cosmic impact event that occurred after last glacial episode. From layer, we extracted n-diamonds and hexagonal diamonds (lonsdaleite), accepted ET indicator, at abundances up to about 5×10 6 times background levels adjacent younger older ice. The NDs concentrated are rounded, suggesting...
A previous investigation revealed that shock-fracturing, a form of low-pressure shock metamorphism in quartz grains, can be produced during near-surface atomic airbursts and cosmic impact structures, most likely at pressures lower than 8 GPa. This discovery implies similar shock-fracturing may also grains exposed to by comets asteroids. Here, we investigate this hypothesis examining sedimentary profile from Abu Hureyra, prehistoric archaeological site northern Syria. was previously proposed...
A widespread platinum (Pt) anomaly was recently documented in Greenland ice and 11 North American sedimentary sequences at the onset of Younger Dryas (YD) event (~12,800 cal yr BP), consistent with YD Impact Hypothesis. We report high-resolution analyses a 1-meter section lake core from White Pond, South Carolina, USA. After developing Bayesian age-depth model that brackets late Pleistocene through early Holocene, we analyzed quantified following: (1) Pt palladium (Pd) abundance, (2)...