Ted E. Bunch

Retired

At Abu Hureyra (AH), Syria, the 12,800-year-old Younger Dryas boundary layer (YDB) contains peak abundances in meltglass, nanodiamonds, microspherules, and charcoal. AH meltglass comprises 1.6 wt.% of bulk sediment, and crossed polarizers indicate that the meltglass is isotropic. High YDB concentrations of iridium, platinum, nickel, and cobalt sugg...

The Younger Dryas (YD) impact hypothesis proposes that fragments of a large, disintegrating asteroid/comet struck the Earth ∼12,800 years ago. This event simultaneously deposited high concentrations of platinum, high-temperature spherules, melt glass and nanodiamonds into the YD boundary layer (YDB) at >50 sites worldwide. Here, we report on a ∼12,...

The Younger Dryas (YD) impact hypothesis posits that fragments of a large, disintegrating asteroid/comet struck North America, South America, Europe, and western Asia ~12,800 years ago. Multiple airbursts/impacts produced the YD boundary layer (YDB), depositing peak concentrations of platinum, high-temperature spherules, meltglass, and nanodiamonds...

This paper overviews the multiple lines of evidence that collectively suggest a Tunguska-like, cosmic airburst event that obliterated civilization-including the Middle Bronze Age (MBA) city-state anchored by Tall el-Hammam-in the Middle Ghor (the 25 km diameter circular plain immediately north of the Dead Sea) ca. 1700 BCE, or 3700 years before pre...

Chapter 8 reviews the evidence for a suspected cosmic impact over North America at the onset of the Younger Dryas climatic period with the near simultaneous extinction of classic Pleistocene megafauna and the Clovis technoculture. The impact related proxies that are used to detect the impact layer, such as spherules, silica-rich glass, nanodiamonds...

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 of which persist within the inner solar system ∼12,800 y later. Evidence suggests that the YDB cosmic impact triggered an “impact winter” and the subsequent Younger D...

Part 1 of this study investigated evidence of biomass burning in global ice records, and here we continue to test the hypothesis that an impact event at the Younger Dryas boundary (YDB) caused an anomalously intense episode of biomass burning at ∼12.8 ka on a multicontinental scale (North and South America, Europe, and Asia). Quantitative analyses...

Download paper at: http://rdcu.be/zYNl ..... Large quantities of impact-related microspherules have been found in fine-grained sediments retained within seven out of nine, radiocarbon-dated, Late Pleistocene mammoth (Mammuthus primigenius) and bison (Bison priscus) skull fragments. The well-preserved fossils were recovered from frozen “muck” deposi...

Previously, a large platinum (Pt) anomaly was reported in the Greenland ice sheet at the Younger Dryas boundary (YDB) (12,800 Cal B.P.). In order to evaluate its geographic extent, fire-assay and inductively coupled plasma mass spectrometry (FA and ICP-MS) elemental analyses were performed on 11 widely separated archaeological bulk sedimentary sequ...

As discussed in Part I, a large accumulation of mammalian faeces at the mire site in the upper Guil Valley near Mt. Viso, dated to 2168 cal 14C yr., provides the first evidence of the passage of substantial but indeterminate numbers of mammals within the time frame of the Punic invasion of Italia. Specialized organic biomarkers bound up in a highly...

Controversy over the alpine route that Hannibal of Carthage followed from the Rhône Basin into Italia has raged amongst classicists and ancient historians for over two millennia. The motivation for identifying the route taken by the Punic Army through the Alps lies in its potential for identifying sites of historical archaeological significance and...

Controversy over the alpine route that Hannibal of Carthage followed from the Rhône Basin into Italia has raged amongst classicists and ancient historians for over two millennia. The motivation for identifying the route taken by the Punic Army through the Alps lies in its potential for identifying sites of historical archaeological significance and...

Abstract

Holliday (1) rejects age-depth models for the Younger Dryas boundary layer (YDB) in Kennett et al. (2), claiming that they are incorrect for several reasons, including age reversals, high age uncertainties, and use of optically stimulated luminescence (OSL) dating. These same claims previously were presented in Meltzer et al. (3) and were discussed...

Significance A cosmic impact event at ∼12,800 Cal B.P. formed the Younger Dryas boundary (YDB) layer, containing peak abundances in multiple, high-temperature, impact-related proxies, including spherules, melt glass, and nanodiamonds. Bayesian statistical analyses of 354 dates from 23 sedimentary sequences over four continents established a modeled...

A major cosmic-impact event has been proposed at the onset of the Younger Dryas (YD) cooling episode at ≈12,800 ± 150 years before present, forming the YD Boundary (YDB) layer, distributed over >50 million km2 on four continents. In 24 dated stratigraphic sections in 10 countries of the Northern Hemisphere, the YDB layer contains a clearly defined...

Petrologic studies of many specimens from a large Northwest African fall suggest a genetic model involving collision of metal impactors with a diogenitic body.

Boslough et al. (1) offer no alternate explanation for ∼10 million tonnes of Younger Dryas spherules recovered from 18 sites across ∼50 million square kilometers of North America, Europe, and the Middle East (2). In addition, the authors claim that our hypothesis “demonstrates a misunderstanding of comets.” However, the misunderstanding is theirs a...

Van Hoesel et al. (1) refer to nanodiamonds at the top of the Usselo horizon at Aalsterhut, The Netherlands, having an average age of 10.845 ± 0.015 14C ka (12.70 ± 0.06 cal ka) (1); they found no nanodiamonds outside hat layer. Earlier, nanodiamonds were reported at the top of the Usselo in Lommel, Belgium, ∼30 km southwest of Aalsterhut, acknowle...

Ives and Froese (1) challenge the identification of the Chobot black mat layer at the Younger Dryas (YD) boundary (YDB), claiming that no black mats have been documented in western Canada (2). To the contrary, Haynes, a lead investigator of YD-age black mats, mapped two YD-age mat sites in western Canada (figure 1 in ref. 3): one ∼200 km south of t...

Impact melt-bearing breccias have been discovered within the proximal ejecta blanket of Meteor Crater, Arizona, for the first time. They contain melt derived from a combination of the projectile and various sedimentary target rocks, including carbonates.

Aubrites are very susceptible to terrestrial weathering, thus making NWA 7214 a rare find in comparison to the nine better known falls.

Significance We present detailed geochemical and morphological analyses of nearly 700 spherules from 18 sites in support of a major cosmic impact at the onset of the Younger Dryas episode (12.8 ka). The impact distributed ∼10 million tonnes of melted spherules over 50 million square kilometers on four continents. Origins of the spherules by volcani...

Iturralde may have formed under natural circumstances unrelated to an impact. However, there is the presence of millions of clusters of glass beads in sediment.

No excess magnetization of the Younger Dryas microspheres refutes the hypothesis that these microspheres could have formed during lightning discharges.

Some mineralogical and bulk compositional features of this unique achondrite match known data for Mercury. Could this be a Hermean meteorite?

This remarkable specimen records impact mixing of two very different highly equilibrated chondritic lithologies (presumably on the CR chondrite parent body).

A diverse assemblage of nanodiamonds found in the Younger Dryas boundary layer (YDB) across North America is consistent with a high-temperature cosmic event at 12.9 ka. Abundance peaks in biomass-burning proxies, such as charcoal, grape-cluster soot, carbon spherules, and glass-like carbon suggest that a major, cross-continental episode of biomass-...

Three ureilites found in Northwest Africa exhibit extreme shock modification of both silicate and carbon phases.

Northwest Africa (NWA) 4797 is an ultramafic Martian meteorite composed of olivine (40.3 vol%), pigeonite (22.2%), augite (11.9%), plagioclase (9.1%), vesicles (1.6%), and a shock vein (10.3%). Minor phases include chromite (3.4%), merrillite (0.8%), and magmatic inclusions (0.4%). Olivine and pyroxene compositions range from Fo66-72,En58-74Fs19-28...

Blaauw et al. (1) take issue with our age–depth model for the Cuitzeo core. They state that no offset for our accelerator mass spectrometry (AMS) 14C dates was quantified, that our identification of the Cieneguillas tephra is doubtful, that we used an outdated calibration model, and they object to our rejection of six AMS dates in the anomalous zon...

It has been proposed that fragments of an asteroid or comet impacted Earth, deposited silica- and iron-rich microspherules and other proxies across several continents, and triggered the Younger Dryas cooling episode 12,900 years ago. Although many independent groups have confirmed the impact evidence, the hypothesis remains controversial because so...

We report the discovery in Lake Cuitzeo in central Mexico of a black, carbon-rich, lacustrine layer, containing nanodiamonds, microspherules, and other unusual materials that date to the early Younger Dryas and are interpreted to result from an extraterrestrial impact. These proxies were found in a 27-m-long core as part of an interdisciplinary eff...

We report results of compositional analyses of 16 new lunar meteorite stones for which names have been approved since our report of last year and speculate about pairing relationships on the basis of composition and preliminary petrographic data.

We refine the systematics of fayalite and chromium contents of olivine within unequilibrated ordinary chondrites as a means of estimating petrologic subtypes and gauging their progressive thermal metamorphism.

Spatially resolved argon isotope measurements have been performed on neutron-irradiated samples of Northwest Africa (NWA) 4797. Shock heating of NWA 4797 completely melted and vesiculated precursor igneous plagioclase, which cooled to an assemblage of plagioclase crystals with interstitial glasses of variable composition (Ca/K ratios). Using a focu...

The eucritic meteorites are basaltic rocks that originate from the upper part of the crust of some small bodies as exemplified possibly by asteroid 4-Vesta. A few eucrites appear to have been modified by different degrees of a late stage alteration process that caused significant variations in mineralogy. Three distinct alteration stages are identi...

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Northwest Africa 5492 is a new metal-rich chondrite breccia that may represent a new oxygen reservoir and new chondrite parent body. It has some textural similarities to CB and CH chondrites, but silicates are more reduced, sulfides are more common and not associated with metal, and metal compositions differ from CB and CH chondrites. Oxygen isotop...

Further characterization of a silicated iron meteorite with textural and mineralogical similarities to Landes.

This eucrite-like specimen has significant petrological and compositional features which make an origin from 4Vesta doubtful.

We describe a highly unequilibrated, ungrouped carbonaceous chondrite with bulk oxygen isotopic composition one-sixth of the way toward the solar value.

Some unequilibrated eucrites display olivine veinlets and secondary anorthite that require the involvement of a late metasomatic agent. Aqueous fluids are plausible candidates for explaining the deposits of the secondary phases inside the cracks.

This highly shocked ultramafic shergottite is the first such martian specimen with "enriched" compositional characteristics.

We report the discovery in the Greenland ice sheet of a discrete layer of free nanodiamonds (NDs) in very high abundances, implying most likely either an unprecedented influx of extraterrestrial (ET) material or a cosmic impact event that occurred after the last glacial episode. From that layer, we extracted n-diamonds and hexagonal diamonds (lonsd...