9 - Was Epipaleolithic Abu Hureyra destroyed by a Comet Airburst at the start of the Younger Dryas?
Or do these Cometians need meteor evidence?
A large number of highly unusual events occurred during the Younger Dryas (YD; 12850 – 11,700 BP[15]):
A ~20 m sea-level rise
An abrupt 10 °C drop in temperature in Central Greenland at the start of the YD and a gradual 5 °C temperature rise over the YD in Antarctica.
A return to colder temperatures in much of Eurasia: the return of alpine-tundra wildflower Dryas octopetala to large parts of Europe, as well as the advance of the Scandinavian ice-sheets.[1]
A return to active volcanism: the Laacher See (Germany) volcano (VEI = 6) around 12,900 years ago [3] as well as Mount St. Helens (USA) during the "Swift Creek Stage" (13,000–10,000 BP)[2]
(Solar) cosmic ray intensity was 50 times higher than present around 16,000 BP, declining to 15 times higher by 12,000 BP. [4]
An abrupt doubling of atmospheric radiocarbon around the start of the YD[5]
An abnormally low geomagnetic field strength, a directional magnetic excursion and a failed geomagnetic reversal around the start of the YD[6]
The peak of the Late Pleistocene megafaunal Extinction that killed off almost 80% of the large to medium-sized mammals in North and South America.[7]
The Younger Dryas Impact Hypothesis (YDIH)
Various authors have presented evidence that the fragments of a large, disintegrating comet caused catastrophic airbursts over North and South America, Europe, and western Asia at the start of the YD[9]. Although a single, self-consistent version of this Younger Dryas Impact Hypothesis (YDIH) has yet to emerge[15] many of the authors suggest these airbursts caused climate change and mass extinctions.
The YDIH has led to an academic spat somewhat similar to the age of the Sphinx fracas, and legions of scientists have joined in the current academic brawl: the YDIH is still highly controversial (e.g. Wikipedia dismisses it). YDIH tenets have recently been severely and comprehensively critiqued by Holliday et al.[15]:
The YDIH invokes a cosmic event at a moment in time to explain complex processes that varied in space and time around the globe. No craters have been identified that date to the onset of the Younger Dryas. The physical evidence offered in support of an impact is nano to microscopic in scale, e.g., charcoal, carbon spherules, magnetic grains/spherules, nanodiamonds, and Pt minerals to name a few. […] There is no obvious evidence of environmental cataclysm at that time in the vast published geomorphic or paleobotanical records. There is no support for the basic premise of the YDIH that human populations were diminished, and individual species of late Pleistocene megafauna became extinct or were diminished due to catastrophe. Evidence and arguments purported to support the YDIH involve flawed methodologies, inappropriate assumptions, questionable conclusions, misstatements of fact, misleading information, unsupported claims, irreproducible observations, logical fallacies, and selected omission of contrary information.
Or in other words: no conclusive case has been made that any of the YD events mentioned at the top were caused by a cosmic impact. The article [15] summarizes the problems of the YDIH authors’ sampling strategies, analysis methodologies and conclusions, whereby reproducibility of YDIH proponents’ results is often an issue, leading to numerous “Is not!” “Is too!” squabbles between various protagonists. Fortunately, for one of the proposed YDIH impact sites, Abu Hureyra, both the arguments for and against come from one and the same author: the cosmic impact proposed by A.M.T. Moore the catastrophist [9-14] can be debunked using the work of A.M.T. Moore the archeologist [8]. A previous post already debunked any speculations that the post-YD Anatolian builders of Göbekli Tepe had any knowledge of or were venerating a (nearby Abu Hureyra) comet strike. This post discusses whether the villagers of Abu Hureyra, an Epipaleolithic village in Northern Syria, witnessed such an event at the start of the YD.
Abu Hureyra
Abu Hureyra is an important pre-historic mound settlement in Northern Syria that was excavated via a set of trenches just before the area was flooded by Lake Assad in 1973. Soil samples taken from a sediment layer ~4 m below the surface contain small quantities of [9,12]:
Microscopic magnetic and glass particles known as microspherules (<0.001 wt%)
Nanodiamonds, diamond nanoparticles smaller than 0.1 µm (10-7 m) (ppb)
Shock-fractured quartz (<0.001 wt%)
Meltglass (~1.6 wt %)
Charcoal (< 1 %)
Elevated concentrations of platinum, nickel, chrome, and cobalt (ppb)
This post will demonstrate:
The author’s Bayesian age model [12] dating this sediment layer is inappropriate and incorrect; its correct age is ~13,000 BP, or over 100 years before the YD.
A lightning strike is the more likely cause of the layer’s features
Even if the unlikely cosmic airburst did occur over or near Abu Hureyra it did not have a catastrophic impact on the area or its fauna and flora.
The age of the proposed YDB layer
The author’s Bayesian model[12] estimated the layer’s age as cal 12,800 ± 40 cal BP, or roughly the start of the YD, so the layer was termed the Younger Dryas Boundary (“YDB”).
The “YDB” layer is defined as the boundary between archeological Phases 1 (Ph1) and 2 (Ph2) of the first Abu Hureyra settlement (AH1), whereby Ph1 pre-dates Ph2[8]. The left part of the figure above is from Moore et al., 2023[12], which is essentially a color version of Figs. 5.7 & 8 from Moore et al., 2000[8] with the Phase information (black and white on the right) left off. Moore et al., 2000[8], estimated the date of the Ph1 to Ph2 transition to14C 11,000 BP (figure below)[8].
The oldest Ph2 sample, OxA – 430, has a 14C age of 11,020 ± 150 BP [8; Table A1], and a sample taken from the Ph1→ Ph2 transition layer, UCIAMS-105429, has a 14C age of 11,070± 40 BP [9, SI Table2] indicating that a 14C age of 11,030-11,110 BP is a robust estimate of the “YDB” age.
Moore et al., 2023 [12] use a Bayesian age-depth model (above) to convert their14C ages to calendar ages and date their “YDB” to cal 12,800 ± 40 BP. This date is however unreliable as their methodology is inappropriate and incorrect. Their type of Bayesian age-depth conversion is only suitable when age varies as a function of depth, for example when modelling the age of (ice or sediment) cores. A Bayesian model incorporates “a priori” (prior) knowledge into the model. In the case of a core this prior knowledge exists in the fact that deeper levels are assumed to be older than shallower levels. The AH1 trench lines (above) however show that archeological levels, such as the proposed “YDB” crosscut numerous depth intervals: the YDB is roughly 50 cm deeper in the North than in the South. The authors have therefore incorrectly modeled younger Ph2 samples e.g. OxA-6685 and OxA-171 (highlighted in blue in the figure) at a depth that is incorrectly deeper than the older UCIAMS-105429 (“YDB”) sample depth.
A simpler approach is to use Moore et al.’s 2000 [8] 14C age estimates for the phase transitions (figure above) – with an assumed uncertainty of 50 years – to generate a Phase – calendar age graph (below).
Several Ph1 samples show an 14C age of around 11,200 BP, confirming that AH1 was likely settled [8] during the Bølling–Allerød interstadial, a period during which the regional climate became warmer and wetter [16,17].
The Ph1 to Ph2 transition – the “YDB” - occurred 30-110 14C years before 11,000 BP (cal 12,950 BP), so very likely during the Bølling–Allerød and 100+ years before the YD. The sample taken from the interval, UCIAMS-105429, whose 14C age of 11,070± 40 BP [9, SI Table2], or cal 13,000 BP (13,090 – 12,900 BP), conclusively places it at least 50 years (95% CI) before the start of the YD (graph below). The best age estimate for the Ph1 to Ph2 transition - and the “YDB” sample layer - is therefore 13,000 cal BP, that is roughly 150 years before the start of the YD.
In summary, the “YDB” does not date to the start of the YD but to 13,000 cal BP, ~150 years earlier, which is roughly concurrent with a geomagnetic field minimum and excursion [6,18], and contemporaneous to a large solar flare/solar proton event that caused a 10Be peak[18], neither of which can be explained by a comet airburst.
A severe lightning strike is a more likely cause of the microscopic “YDB” evidence
Soil samples taken from the “YDB” layer contained small quantities of [9,12]:
Microscopic magnetic and glass particles known as microspherules (<0.001 wt%)
Meltglass (~1.6 wt %)
Charcoal (< 1 %)
Nanodiamonds, diamond nanoparticles smaller than 0.1 µm (10-7 m) (ppb)
Shock-fractured quartz (<0.001 wt%)
Elevated concentrations of platinum, nickel, chrome, and cobalt (ppb)
The first three suggest a high temperature heat source melted some of the local sediment grains: temperatures in excess of 1720 °C were reportedly required, ruling out most anthropogenic and natural heat sources [9,12]. Lightning strikes can locally heat sediments to temperatures in excess of 25,000 °C.[19] Any heat source must have been at a distance as the low concentrations suggest the grains were blasted, carried, trampled, shovelled, etc. in from elsewhere.
Nanodiamonds and shock-fractured quartz are often taken to be indicative of high temperatures and pressures: nanodiamonds are commercially produced via explosions. Moore et al., 2023 [11] claim pressures in excess of 5.5 GPa are required to produce shock-fractured quartz and nanodiamonds, which is in the higher ranges of what can be expected by a large airburst. Lightning strikes can produce pressures in excess of 7 GPa. [20]
Finally, elevated concentrations of platinum, nickel, chrome, and cobalt are commonly associated with meteor impacts, although elevated concentrations are problematic for both fragmented comet airburst and lightning scenarios. The chemical composition of the “YDB” sample closely matches that of the soil surrounding Abu Hureyra, indicating very little cosmic material is present in the sample [9,10,12]. Tektites and microtektites were not found. This is consistent with a comet fragment airburst: most comets are “dirty snowballs” that largely consist of ice and solid CO2, with only small amounts of “cosmic dust”. Upon atmospheric entry the comet fragment heats due to atmospheric friction, whereby the ice and CO2 start to boil off, destabilizing the comet fragment and often causing it explode before impact in an airburst, whereby its minor amounts of solids are distributed over a large area. Any local metal enrichment therefore likely comes from a different source. Abu Hureyra is located on the banks of the Euphrates, whose drainage area includes much of Syria and Southern Turkey. Its waters are therefore enriched in Cr, Ni, Co, and PGE elements derived from the erosion of the Syrian and Turkish Pliocene volcanics, e.g. the Ghab Pliocene volcanic field [21]. These heavy metals likely accumulated in the flora and fauna that lived near the floodplain, and were therefore likely enriched in the ash deposits of any “YDB” airburst/lightning-caused fire. Modern forest fires similarly often enrich trace elements such as Cr, Co and Ni [24]
Another possible source of the elevated concentrations is cosmic dust. The geomagnetic field strength was very low around cal 13,000 BP [6], so was no longer efficiently repelling positive cosmic dust ions (such as Cr3+, Ni2+, etc.). A low geomagnetic field strength would also partially collapse the Van Allen belts, the region in the Earth’s magnetosphere where cosmic ions are trapped, resulting in an increase in cosmic ion deposition. Cosmic dust is chemically indistinguishable from meteoric/comet material.
Lightning strike sediments can be (microscopically) virtually identical to cosmic airburst deposits, a fact that was noted upon by the YDIH proponents [9,10 Table 2,12]. Bunch et al. [9] dismiss lightning as a possible cause as the lateral distribution of materials at Abu Hureyra (4.5 m) exceeds the distance (<1 m) at which they claim lightning strikes typically disperse materials. No reference supporting this claim is mentioned however, and even relatively minor lightning strikes reportedly have dispersed macroscopic material over distances > 5 m [22]. Moore et al., 2020[10] dismiss lightning as a possible cause as they claim the magnetic remanence of 6 Fe-rich magnetic spherules extracted from the YDB layer was lower than the range characteristic of lightning. The “range characteristic of lightning” was however determined from an article [23] on lodestones, naturally occurring magnets. These high magnetic remanence lodestones are however always rich in mineral maghemite - a fact not in evidence for the “YDB” spherules - and typically only occur “5-10 cm from the center of the strike”[23]. The article indicates the magnetic remanence of other lightning-struck materials is almost always low (<0.05) “regardless of the type of material or the degree of magnetic hardness” and that high remanence (>0.2) occurs only in lodestones.[23] Lightning struck spherules can therefore also be expected to have low magnetic remanence.
In summary, none of the microscopic evidence is uniquely indicative of a comet airburst. Given that lightning strikes the Earth 44 times per second, and large comet airbursts are rare events that happen once every few centuries, and enormous fragmenting comet airbursts over an area spanning half the globe have possibly never occurred, the probability that the “YDB” layer was caused by a lightning strike is orders of magnitude greater than that of a comet airburst. A future post will demonstrate that around cal 13,000 BP the probability of very powerful “positive” lightning strikes was significantly higher.
Did a comet airburst happen at Abu Hureyra?
The previous section demonstrated that a lightning strike very likely occurred around cal 13,000 BP at Abu Hureyra, although a very improbable comet airburst cannot be entirely ruled out. If a comet airburst did happen then it occurred ~150 years before the YD, and therefore does not benefit from being included in the YDIH, and vice versa. In addition, it did not really do much macroscopic damage and only minor amounts of microscopic damage. One could be forgiven for wondering “Where’s the catastrophe?” for this exceedingly insignificant and minor non-event.
If a cosmic airburst did occur over Abu Hureyra, it did not cause mass extinctions in the area or even in the village: Moore et al., 2000 [8] mention numerous times that the AH1 village was continuously inhabited, e.g. pg. 180:
The settlement of AH1 lasted for about 1,500 radiocarbon years, apparently without interruptions.
pg 477:
the same group of people continued to inhabit the village without interruption
Moore et al., 2023 [12] claim their cosmic airburst had roughly double the energy of the Tunguska event, which “flattened an estimated 80 million trees over an area of 2,150 km2”. AH1 inhabitants seldom strayed more than 15 km from their village [8], so likely would have either been killed outright by an airburst, or would have starved in the period thereafter due to the disappearance of all their food in the ecological catastrophe that followed. However, the population grew between Ph1 and Ph2, and no malnutrition or large shifts in diet were noted by Moore et al., 2000 [8]. No mass extinction of people, fauna, or flora is documented, and the inhabitants did not relocate. No drastic climate change occurred: the regional climate generally became slightly cooler and wetter during the YD, though the winters became dryer [16].
The only major change that occurred between Ph1 and Ph2 is a change in housing style. Moore et al. 2000 [8] reported that Ph1 huts typically consisted of vertical wooden posts surrounding fire pits, roofs of interwoven branches covered with reeds, grasses, and, possibly, animal skins, and exterior walls covered with reed mat [8]. A lightning strike would likely have caused a few huts - possibly the whole village - to catch fire and burn down. AH1 was one of the first human settlements ever, so the inhabitants would have still been experimenting with housing technology. They would have likely learned - the hard way - that building a house out of flammable materials over a fire pit was an accident waiting to happen, and rebuilt Ph2 huts differently. The Ph2 huts were constructed above ground over the filled-in Ph1 fire pits.
In summary: if a cosmic airburst happened over Abu Hureyra than it happened ~150 years before the YD and did not cause climate change, mass extinctions or any other catastrophic damage in the Abu Hureyra area. The observed microscopic changes were very likely caused by a lightning strike. The next posts will demonstrate that violent, “positive” lightning strikes were very likely around cal 13,000 BP and that mythical comet impacts did not cause any catastrophic damage at the end of the last ice age.
References:
[1] Andersen, B., Borns, H., 1994, The Ice Age World: An Introduction to Quaternary History and Research with Emphasis on North America and Northern Europe During the Last 2.5 Million Years. Oxford University Press, ISBN: 978-8200218104
[2] Mullineaux, D., 1996, Pre-1980 Tephra-Fall Deposits Erupted From Mount St. Helens, Washington. U.S. Geological Survey Professional Paper 1563
[3] Schmincke, H.; Park, C.; Harms, E., 1999, Evolution and environmental impacts of the eruption of Laacher See Volcano (Germany) 12,900 a BP. Quaternary International, 61, 61–72. doi:10.1016/S1040-6182(99)00017-8.
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[5] LaViolette, P. A., 2011, Evidence for a solar flare cause of the Pleistocene mass extinction, Radiocarbon 53, p 303-323.
[6] Pavón-Carrasco, F.J., Osete, M.L., Torta, J.M., De Santis, A., 2014, A geomagnetic field model for the Holocene based on archaeomagnetic and lava flow data, Earth and Planetary Science Letters, 388, 98-109, //doi.org/10.1016/j.epsl.2013.11.046.
[7] Channell, J. , Vigliotti, L., 2019, The Role of Geomagnetic Field Intensity in Late Quaternary Evolution of Humans and Large Mammals. Reviews of Geophysics, 57, 709–738, doi:10.1029/2018RG000629.
[8] Moore, A., Hillman, G., Legge, A., 2000, Village on the Euphrates: From Foraging to Farming at Abu Hureyra. Oxford: Oxford University Press. ISBN 0-19-510806-X.
[9] Bunch, T., Hermes, R., Moore, A. et al, 2012, Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago. PNAS, v. 109, E1903-E191, https://doi.org/10.1073/pnas.1204453109
[10] Moore, A., Kennett, J. Napier, W. et al., 2020, Evidence of Cosmic Impact at Abu Hureyra, Syria at the Younger Dryas Onset (~12.8 ka): High-temperature melting at >2200 °C. Sci Rep, v. 10, 4185. https://doi.org/10.1038/s41598-020-60867-w
[11] Moore, A., Kennett, J. et al., 2023, Abu Hureyra, Syria, Part 1: Shock-fractured quartz grains support 12,800-year-old cosmic airburst at the Younger Dryas onset. Airbursts and Cratering Impacts, 1. DOI: 10.14293/ACI.2023.0003
[12] Moore, A., Kennett, J. et al., 2023, Abu Hureyra, Syria, Part 2: Additional evidence supporting the catastrophic destruction of this prehistoric village by a cosmic airburst ~12,800 years ago. Airbursts and Cratering Impacts, 1. DOI: 10.14293/ACI.2023.0002
[13] Moore, A., Kennett, J. et al., 2023, Abu Hureyra, Syria, Part 3: Comet airbursts triggered major climate change 12,800 years ago that initiated the transition to agriculture. Airbursts and Cratering Impacts, 1. DOI: 10.14293/ACI.2023.0004
[14] Hermes, R., Wenk, H., 2023, Microstructures in shocked quartz: linking nuclear airbursts and meteorite impacts. Airbursts and Cratering Impacts, 1. DOI: 10.14293/ACI.2023.0001
[15] Holliday, V., Daulton, T., et al., 2023, Comprehensive refutation of the Younger Dryas Impact Hypothesis (YDIH). Earth-Science Reviews, 247, 104502, https://doi.org/10.1016/j.earscirev.2023.104502.
[16] Dafna Langgut, D., Cheddadi, R., Sharon, G., 2021, Climate and environmental reconstruction of the Epipaleolithic Mediterranean Levant (22.0–11.9 ka cal. BP), Quaternary Science Reviews, 270, 107170, https://doi.org/10.1016/j.quascirev.2021.107170.
[17] Willcox, G., Buxo, R., & Herveux, L., 2009, Late Pleistocene and early Holocene climate and the beginnings of cultivation in northern Syria. The Holocene, 19, 151-158. https://doi.org/10.1177/0959683608098961
[18] Channell, J.,Vigliotti, L., 2019, The Role of Geomagnetic Field Intensity in Late Quaternary Evolution of Humans and Large Mammals. Reviews of Geophysics, 57, 709–738. doi:10.1029/2018RG000629.
[19] Blumenthal R., 2016, The Explosive Effects of Lightning: What are the Risks? Acad Forensic Pathol., 6, 89-95. doi: 10.23907/2016.008.
[20] Chen, J., Elmi, C., et al., 2017, Generation of shock lamellae and melting in rocks byl ightning-induced shock waves and electrical heating, Geophys. Res. Lett., 44, 8757–8768, doi:10.1002/2017GL073843
[21] Al-Mishwat, A., Dawod, S., 2021, Geochemistry and Petrogenesis of Basaltic Rocks and Enclosed Xenoliths from the Ghab Pliocene Volcanic Field in Northwestern Syria. International Journal of Geosciences, 12, 667-688. https://doi.org/10.4236/ijg.2021.128038
[22] Blumenthal R., 2012, Secondary missile injury from lightning strike. Am J Forensic Med Pathol., 33, 83-5. http://dx.doi.org/10.1097/paf.0b013e31823a8c96
[23] Wasilewski, P. & Kletetschka, G., 1999, Lodestone: Natures only permanent magnet‐What it is and how it gets charged. Geophys Res Lett., 26, 2275–2278.
[24] Abraham, J., Dowling, K. & Florentine, S. The Unquantified Risk of Post-Fire Metal Concentration in Soil: a Review. Water Air Soil Pollut 228, 175 (2017). https://doi.org/10.1007/s11270-017-3338-0