The Younger Dryas Impact Hypothesis: A Cometary Encounter at 12,800 BP, Nineteen Years of Argument, and Where the Question Stands.

What the hypothesis is, in a paragraph.

The Younger Dryas Impact Hypothesis (YDIH), as formulated in the 2007 Firestone et al. paper in PNAS and developed across subsequent publications, proposes that approximately 12,800 calendar years before present, multiple cometary fragments — possibly a single body broken into pieces during atmospheric entry — impacted the Laurentide Ice Sheet over North America and possibly other regions of the Northern Hemisphere, producing a combination of direct kinetic effects, atmospheric injection of dust and aerosols, large-scale biomass burning, and freshwater pulses into the North Atlantic from accelerated ice-sheet melt. The proposed consequences: (1) the abrupt onset of the Younger Dryas climatic cooling, a roughly 1,200-year return to near-glacial conditions that interrupted the broader post-glacial warming; (2) the collapse of late Pleistocene megafaunal populations in North America (mammoths, mastodons, giant ground sloths, several large carnivores) on a timescale compressed enough that an impulsive trigger is required; (3) the disruption of the Clovis culture, the earliest widely-recognized Paleoindian archaeological horizon in North America, whose distinctive fluted-point tradition appears to terminate at or near the onset of the Younger Dryas. The proposed material evidence: a distinct sedimentary horizon — the "Younger Dryas Boundary" (YDB) layer, sometimes designated as a "black mat" of organic-rich material — identified at sites from Murray Springs (Arizona) to Hall's Cave (Texas) to Lake Cuitzeo (Mexico) to Lommel (Belgium) and elsewhere across the Northern Hemisphere, containing claimed impact-proxy markers including nanodiamonds, magnetic and carbon spherules, high-temperature melt glass, and elevated platinum-group element concentrations. The hypothesis has been the subject of sustained scientific contestation across nineteen years. The mainstream Quaternary-science consensus has not adopted it; specific lines of evidence have been challenged (most notably the reproducibility of the nanodiamond claims), and alternative explanations for each individual phenomenon (the Younger Dryas cooling itself, the megafaunal extinctions, the Clovis disruption) have been or remain available within mainstream frameworks. At the same time, the hypothesis has not been definitively closed: the platinum anomaly recovered from the Greenland Ice Sheet (Petaev et al., 2013) provides a stratigraphically-resolved data point that is broadly consistent with impact-style deposition; the 2018 Wolbach et al. multi-author papers expanded the evidence base substantially; the 2020 Sweatman "encyclopedic" review presented an integrated case at length. The hypothesis is the object of continuing peer-reviewed publication and continuing peer-reviewed criticism. It is, in the language we apply to such cases in this archive, a respectable minority hypothesis with credentialed proponents and a continuing publication record — not the mainstream consensus position in Quaternary science, but not in the same evidentiary category as fringe pseudoarchaeology, despite the popular extension of the hypothesis by Graham Hancock and others that has tended to conflate the two in public discourse.

The documented record.

The Younger Dryas itself

The Younger Dryas is a well-established stratigraphic and climatic interval, named after the alpine flower Dryas octopetala whose pollen marks the period in European sediments. It refers to a roughly 1,200-year return to near-glacial conditions, beginning approximately 12,900 years before present and ending approximately 11,700 years before present. The cooling is recorded in ice cores from Greenland (most precisely in GISP2 and NGRIP), in deep-sea sediment cores from the North Atlantic, in lake-sediment records across Europe and North America, and in pollen records. The onset was abrupt — Greenland ice core records resolve the temperature transition on a timescale of less than a few decades; the termination was also abrupt. Verified [1]

The cause of the Younger Dryas is itself the subject of long-standing debate in Quaternary science. The leading mainstream explanation has been the "meltwater hypothesis" (Broecker and colleagues): a massive freshwater pulse from glacial Lake Agassiz draining through the St. Lawrence or Mackenzie River systems into the North Atlantic disrupted the Atlantic Meridional Overturning Circulation, shutting down the heat-transport that maintains the relatively warm climate of the North Atlantic region. The meltwater hypothesis has substantial support but has its own difficulties (the specific freshwater-discharge pathway has been hard to identify with certainty, and the timing has been refined repeatedly). Verified as the dominant mainstream framework, but not as a fully closed question.

The 2007 Firestone et al. paper

In October 2007, R.B. Firestone, A. West, J.P. Kennett, L. Becker, T.E. Bunch, Z.S. Revay, P.H. Schultz, T. Belgya, D.J. Kennett, J.M. Erlandson, O.J. Dickenson, A.C. Goodyear, R.S. Harris, G.A. Howard, J.B. Kloosterman, P. Lechler, P.A. Mayewski, J. Montgomery, R. Poreda, T. Darrah, S.S. Que Hee, A.R. Smith, A. Stich, W. Topping, J.H. Wittke, and W.S. Wolbach published "Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling" in the Proceedings of the National Academy of Sciences. Verified [2]

The paper presented a set of claimed impact-proxy markers identified at multiple sites across North America and one site in Belgium. The markers included: magnetic microspherules; iridium and other platinum-group element enrichments; nanodiamonds (carbon nanoparticles with diamond crystal structure); high-temperature melt glass; fullerenes containing extraterrestrial-pattern helium isotopes; and a charcoal-and-organic-rich "black mat" sedimentary layer at the proposed boundary. The paper proposed that the cumulative evidence supported a cometary impact — possibly multiple airbursts rather than a single ground-impact crater — over the Laurentide Ice Sheet at approximately 12,900 calendar years before present.

The proposed impact mechanism and consequences

The Firestone paper and subsequent YDIH publications have refined the proposed mechanism. The current YDIH framing posits one of two possibilities: a single comet of approximately 4 km diameter that fragmented during atmospheric entry, with multiple fragments impacting the Laurentide Ice Sheet and adjacent regions; or a smaller comet that produced a series of airbursts without surface impact craters. The hypothesis emphasizes airburst (rather than ground-strike) mechanisms in order to account for the absence of any identified impact crater of the proposed age and scale. Claimed [3]

The proposed downstream consequences: direct kinetic effects on the ice sheet (catastrophic melt, freshwater pulse into the North Atlantic), atmospheric injection of dust and sulfate aerosols (climate forcing), large-scale biomass burning across the Northern Hemisphere (the carbonaceous "black mat" interpreted as a synchronous-burn deposit), and trophic-cascade effects on the late Pleistocene fauna. The Clovis disruption is interpreted as the human-cultural manifestation of the broader ecological reorganization.

The Greenland platinum anomaly (Petaev et al., 2013)

In 2013, M.I. Petaev, S. Huang, S.B. Jacobsen, and A. Zindler published in PNAS a stratigraphically-resolved analysis of platinum concentrations in the GISP2 Greenland ice core covering the Younger Dryas onset. Verified [4] The analysis identified a sharp platinum-concentration peak at the Younger Dryas onset, with platinum/iridium and platinum/aluminum ratios that the authors interpreted as consistent with deposition from an impactor of unusual composition (specifically, an iridium-poor, platinum-rich body, possibly a fragment of a metallic asteroid or an unusual cometary nucleus).

The Greenland platinum anomaly has been broadly accepted as an empirically real feature of the GISP2 record. Its interpretation has been contested: the anomaly is consistent with impact-style deposition but may also be consistent with other origins, including volcanic outgassing of unusual composition or terrestrial weathering effects under the meltwater-pulse conditions. The platinum data is one of the YDIH's strongest single pieces of evidence, in part because it comes from a well-controlled high-resolution ice-core stratigraphy independent of the YDB-site terrestrial sediment record.

The Hall's Cave, Murray Springs, Lake Cuitzeo, and Lommel sites

The YDIH proposes the YDB layer as a stratigraphic marker identifiable at multiple sites across the Northern Hemisphere. The most extensively studied sites include: Verified as documented site studies; Disputed as to whether the markers in fact constitute a synchronous impact horizon.

• Murray Springs, Arizona. A Clovis-era archaeological site with a well-stratified Younger Dryas Boundary sediment layer. YDIH proponents have reported impact-proxy markers; the same layer has been re-examined by other researchers with mixed results.
• Hall's Cave, Texas. A stratified cave deposit with continuous sedimentation across the Younger Dryas transition. YDIH-related platinum and microspherule peaks have been reported at the Younger Dryas onset (Sun et al., 2020 study reproduced the platinum peak at this site).
• Lake Cuitzeo, Mexico. Lake-sediment record with reported YDB markers (Israde-Alcántara et al., 2012, PNAS).
• Lommel, Belgium. The European reference site; reported nanodiamond and microspherule signatures.
• Abu Hureyra, Syria. A Levantine site with reported melt-glass evidence, interpreted by YDIH proponents (Moore et al., 2020) as evidence of an airburst event affecting the site.

The 2018 Wolbach et al. multi-author papers

In 2018, W.S. Wolbach and approximately twenty-three coauthors published a pair of long papers in the Journal of Geology presenting an extensive integrated case for the YDIH, with particular emphasis on biomass-burning evidence across the Younger Dryas Boundary. The papers reviewed the proxy data, presented new charcoal and combustion-aerosol data, and argued for hemispheric-scale burning at the YDB. Verified as publication; Claimed regarding the burning-scale interpretation [5].

The 2020 Sweatman review

In 2021 (publication date), Martin B. Sweatman of the University of Edinburgh published "The Younger Dryas impact hypothesis: review of the impact evidence" in Earth-Science Reviews, an integrated multi-decade survey of the published evidence and arguments. Sweatman's review concluded that the case for the YDIH was substantially strengthened by the accumulated post-2007 evidence and that the hypothesis warranted serious consideration as the leading candidate explanation for the Younger Dryas onset. Claimed [6]

The mainstream counterarguments

The mainstream scientific reception of the YDIH has been substantially critical. Notable counter-arguments include: Verified

• Pinter et al. (2011) in Earth-Science Reviews presented a comprehensive review titled "The Younger Dryas impact hypothesis: a requiem," reporting that independent attempts to reproduce key YDIH evidence had largely failed and that the cumulative case was unsupported [7].
• Kerr (2010, 2014) in Science news coverage and reviews summarized the unsuccessful reproduction attempts and the mainstream skepticism [8].
• Holliday et al. (2014, 2023) have argued that the YDB stratigraphic horizon is not as cleanly defined as YDIH proponents claim, that the proposed markers do not co-occur consistently across the proposed sites, and that the dating of the markers is not as tightly constrained as a synchronous impact event would require [9].
• Buchanan et al. on the Clovis-disruption side have argued that the demographic and archaeological record of Clovis termination does not in fact require an impulsive trigger; that conventional climatic and demographic explanations are adequate; and that the case for a YDIH-driven Clovis collapse is weak [10].
• Nanodiamond reproduction. Independent attempts to identify YDB nanodiamonds at proposed YDIH sites have produced mixed and frequently null results. The original nanodiamond claim — one of the strongest in the 2007 paper — has been one of the most extensively contested. Disputed.

The Hancock popular extension

Graham Hancock, in Magicians of the Gods (2015), the Netflix series Ancient Apocalypse (2022; second season 2024), and subsequent works, has popularized the YDIH and combined it with his pre-existing thesis of a lost advanced civilization predating the Younger Dryas. In Hancock's framing, the Younger Dryas impact event destroyed an advanced civilization whose survivors transmitted agricultural and architectural knowledge to subsequent Holocene peoples, explaining the apparent "sudden" appearance of agriculture and monumental architecture in the early Holocene. Claimed

What the evidence shows: The narrow YDIH (a cometary impact at ~12,800 BP) and the broader Hancock thesis (a pre-impact advanced civilization) are different claims with different evidentiary burdens. The YDIH is a hypothesis about geological and climatological evidence and is the subject of peer-reviewed contestation. The pre-impact-civilization thesis has no independent archaeological evidentiary base of comparable character; it rests on inference from the YDIH plus reinterpretation of post-Younger-Dryas archaeology (Göbekli Tepe, Egypt, the Andean megalithic record) as descendants of a lost predecessor. Unverified at the level of the pre-civilization thesis. The conflation of the two in popular discourse has, on balance, hindered the YDIH's reception in mainstream scholarship by associating a contestable but credentialed scientific hypothesis with a broader narrative that has no comparable evidentiary base.

The hypotheses in play.

The full YDIH: cometary impact triggers Younger Dryas + megafaunal extinction + Clovis disruption

The Firestone-Kennett-West formulation. Claimed

Where it stands: Has continuous peer-reviewed publication from 2007 onward, including in PNAS, Journal of Geology, Quaternary Science Reviews, and Earth-Science Reviews. Has substantial counter-publication from the mainstream Quaternary-science community. Has the Greenland platinum anomaly (Petaev et al., 2013) as a high-quality single data point that constrains the discussion. Is not the consensus position in the field. The status as of 2026 is that the hypothesis is taken seriously enough to be the subject of continuing peer-reviewed back-and-forth and is not treated by the mainstream as closed; it is also not treated by the mainstream as established.

A narrow Younger Dryas impact (cooling trigger only)

A weaker version: an impact event occurred at ~12,800 BP and contributed to the Younger Dryas cooling onset, without necessarily being the cause of the megafaunal extinctions or the Clovis disruption (which may have separate or compound causes). Claimed

Where it stands: This weaker version is more compatible with the evidence than the full YDIH, in the sense that the platinum anomaly and the YDB-layer chemistry are best constrained to the impact-and-climate question. The narrower version reduces the explanatory burden the hypothesis must carry while preserving its core empirical claim. Mainstream reception of this narrower formulation has also been mixed but is somewhat less skeptical than reception of the full hypothesis.

The conventional meltwater-pulse explanation (mainstream)

The Broecker / Carlson lineage. Argument: a glacial-lake outburst flood (specifically Lake Agassiz, possibly draining via the Mackenzie or St. Lawrence) delivered a freshwater pulse to the North Atlantic of sufficient magnitude to disrupt the AMOC and produce the cooling. The megafaunal extinctions reflect a separate combination of climate change and human overhunting; the Clovis disruption reflects demographic and ecological pressures during the cooling. Verified as the mainstream framework; Disputed as to whether it fully accounts for the abruptness of the onset and the specific freshwater-pathway evidence.

Combined or multi-cause explanations

Increasingly common in the recent literature: a combination of meltwater forcing, possibly compounded by a smaller impulsive event (volcanic or impact-related), with separate demographic and ecological drivers of the megafaunal and Clovis components. Claimed

Where it stands: The combined formulations are increasingly mainstream-tolerant, in the sense that they accommodate the platinum anomaly and the abruptness of the cooling onset without requiring the full YDIH framework. The combined approach reduces the polarization of the debate but at the cost of leaving the individual causal contributions less than fully specified.

The Hancock pre-impact-civilization extension

The popular extension. Claimed

Where it stands: Not a peer-reviewed scientific hypothesis. Rests on inference from the YDIH plus reinterpretation of post-Holocene archaeology rather than on direct evidence of a pre-Younger-Dryas advanced civilization. The Göbekli Tepe construction date of approximately 9600 BCE places that site after, not before, the Younger Dryas; the Hancock thesis requires either pushing the Göbekli Tepe construction earlier (which the radiocarbon record does not support) or treating Göbekli Tepe as a successor-civilization artifact (which is consistent with but not evidence for a predecessor). Unverified.

The unanswered questions.

An identified crater (or comprehensive airburst-mechanism case)

The single most significant evidentiary gap in the YDIH. A ~4 km cometary body striking the Laurentide Ice Sheet should, in conventional impact mechanics, produce an identifiable crater. No crater of the proposed age has been identified. YDIH proponents have shifted toward airburst formulations in part to address this gap, but airburst mechanisms of the proposed scale require their own substantial physical case — a sustained set of airbursts producing hemispheric biomass burning and platinum-anomaly-scale deposition is an extreme proposition that requires evidence beyond the absence of a crater. The Hiawatha Glacier crater (Greenland, identified in 2018) was initially proposed as a possible YDIH candidate, but subsequent dating work has placed Hiawatha at approximately 58 million years before present rather than 12,800, eliminating it as a YDIH candidate.

Reproducibility of the nanodiamond evidence

The 2007 paper's nanodiamond identification has been one of the most contested empirical claims of the YDIH. Independent attempts to identify YDB nanodiamonds at proposed sites have produced mixed and frequently null results. The technique itself is sensitive to sample preparation, and the interpretation of identified nanodiamonds as impact products requires ruling out other plausible origins (biomass burning, terrestrial contamination). Whether the YDB nanodiamond signal exists at the level the YDIH requires is, as of 2026, not resolved.

The dating tightness of the YDB layer across sites

A synchronous-impact hypothesis requires the YDB layer to be tightly contemporaneous across all proposed sites. The dating uncertainty at most sites is at the level of one to several centuries; whether the proposed markers in fact converge on a single sharp date or are spread across a broader interval is contested. The Greenland ice-core dating is the most precise; the terrestrial sediment dating is intrinsically less precise.

The megafaunal-extinction temporal structure

The North American megafaunal extinctions are recorded as a compressed but not instantaneous event. The temporal structure of the extinctions — whether they correspond to a single sharp pulse at the YDB or are spread across a broader Younger Dryas interval — is a substantial body of independent paleoecological work. Whether the extinction timing is tight enough to require an impulsive trigger or is consistent with a more gradual combination of climate and human-pressure causes is the subject of continuing debate independent of the YDIH question.

The Clovis-disruption demographic argument

Whether the apparent termination of Clovis fluted-point technology at or near the Younger Dryas onset reflects a population collapse (consistent with the YDIH) or a cultural-technological transition without dramatic demographic change (the position advanced by Buchanan et al.) is itself contested. The Clovis archaeological record is sufficiently limited that the demographic question is hard to resolve definitively from the surviving material.

Primary material.

• The original Firestone et al. paper (PNAS, 2007), and the dataset of YDB markers it presented.
• The Petaev et al. paper (PNAS, 2013) on the Greenland platinum anomaly, with the GISP2 ice-core data.
• The Wolbach et al. papers (Journal of Geology, 2018) on biomass burning evidence.
• The Moore et al. paper (Scientific Reports, 2020) on the Abu Hureyra meltglass evidence.
• The Sweatman review (Earth-Science Reviews, 2021).
• The Pinter et al. "Requiem" paper (Earth-Science Reviews, 2011) and subsequent Holliday et al. critiques.
• The Greenland ice-core records (GISP2, NGRIP) covering the Younger Dryas transition.
• The terrestrial site stratigraphies at Murray Springs, Hall's Cave, Lake Cuitzeo, Lommel, Abu Hureyra, and others.
• The North American megafaunal extinction record (FAUNMAP and successor databases).
• The Clovis archaeological record (PIDBA database and primary site reports).

The sequence.

1. ~12,900 years BP Onset of the Younger Dryas cooling, as recorded in Greenland ice cores and North Atlantic sediments. Onset interval estimated at decades.
2. ~12,800 years BP The hypothesized YDIH impact event. Termination of Clovis-tradition technology in the North American archaeological record approximately contemporary.
3. ~11,700 years BP Termination of the Younger Dryas; onset of the Holocene warm period.
4. 1968 Wallace Broecker proposes the basic AMOC-disruption framework for North Atlantic abrupt climate events.
5. 1980s–1990s The meltwater-pulse / AMOC-disruption explanation becomes the mainstream framework for the Younger Dryas.
6. May 2007 Initial presentation of the YDIH proposal at the Joint Assembly of the American Geophysical Union, Acapulco.
7. October 9, 2007 Firestone et al. paper published in PNAS.
8. 2008–2010 Initial scientific reception. Mixed; substantial skepticism.
9. 2011 Pinter et al. "Requiem" paper published in Earth-Science Reviews. Mainstream rejection consolidated.
10. 2012 Israde-Alcántara et al. report YDB markers at Lake Cuitzeo, Mexico (PNAS).
11. 2013 Petaev et al. publish Greenland platinum anomaly (PNAS). Significant single data point in favor of the YDIH.
12. 2014–2017 Continuing back-and-forth in the literature. Holliday et al. critiques. Comet Research Group continues YDIH publication.
13. 2018 Wolbach et al. publish biomass-burning papers in Journal of Geology. Hiawatha Glacier crater identified in Greenland (initially proposed as possible YDIH candidate).
14. 2019–2022 Hiawatha crater dated to ~58 Ma; eliminated as YDIH candidate.
15. 2020 Moore et al. report Abu Hureyra airburst evidence in Scientific Reports. Sun et al. confirm platinum peak at Hall's Cave.
16. 2021 Sweatman publishes integrated review in Earth-Science Reviews.
17. 2022 Hancock's Netflix series Ancient Apocalypse popularizes the broader thesis.
18. 2023–2026 Continuing peer-reviewed publication and counter-publication. No mainstream-consensus resolution. Holliday et al. 2023 sustained critique reinforces the skeptical mainstream position.

Cases on this archive that connect.

Göbekli Tepe (File 012) — the directly related case. The Göbekli Tepe construction date of ~9600 BCE places it after the Younger Dryas. YDIH proponents and Hancock-tradition popular writers have variously argued that Göbekli Tepe represents either a survivor culture from the pre-impact world or evidence of the post-impact reorganization of human social complexity. The Göbekli Tepe Pillar 43 "Vulture Stone" has been the focus of specific astronomical-decoding claims (Sweatman, 2017) connecting the site to the YDIH; the DAI excavation team rejects this decoding.

Atlantis (File 057) — for the popular extension of the YDIH into the Atlantis narrative via the Hancock thesis. Plato's Atlantis description places the destruction at approximately 9,000 years before his time (i.e., approximately 11,500 years before present), which is broadly consistent in chronological order with the Younger Dryas. The connection has been advanced in popular literature; it is not supported by Plato-scholarship or by independent archaeological evidence for an advanced pre-Holocene civilization.

The Tunguska Event (File 016) — the best-documented airburst event in the modern historical record, providing the conceptual model for the airburst mechanism the YDIH increasingly relies on. Tunguska (1908) was a single airburst of an estimated ~50 m bolide; the YDIH proposes airbursts orders of magnitude larger, raising the question of whether the Tunguska model scales.

The Sphinx Weathering Hypothesis (File 071) — structural parallel of a non-consensus minority hypothesis with credentialed proponents (Schoch in that case, Firestone-Kennett-West in this one) contesting a mainstream archaeological or earth-science consensus. The case-shape parallels are instructive: in both cases, the minority hypothesis has continuing peer-reviewed publication and continuing peer-reviewed rejection.

Planned: a standalone file on the Pleistocene megafaunal extinctions as a Quaternary-science question; a file on the Clovis-first vs. pre-Clovis archaeological debate.

Full bibliography.

1. Alley, R.B., et al. "Abrupt climate change." Science 299, 2005–2010 (2003). On the Younger Dryas as an abrupt-climate-change event of high analytical importance.
2. Firestone, R.B., West, A., Kennett, J.P., Becker, L., Bunch, T.E., et al. "Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling." Proceedings of the National Academy of Sciences 104(41), 16016–16021 (October 9, 2007).
3. Kennett, J.P., et al. Multiple subsequent papers in PNAS, Quaternary Science Reviews, and Journal of Geology, 2008–2024.
4. Petaev, M.I., Huang, S., Jacobsen, S.B., and Zindler, A. "Large Pt anomaly in the Greenland ice core points to a cataclysm at the onset of Younger Dryas." Proceedings of the National Academy of Sciences 110(32), 12917–12920 (August 6, 2013).
5. Wolbach, W.S., et al. "Extraordinary biomass-burning episode and impact winter triggered by the Younger Dryas cosmic impact ~12,800 years ago." Parts 1 and 2, Journal of Geology 126, 165–217 and 219–253 (2018).
6. Sweatman, M.B. "The Younger Dryas impact hypothesis: review of the impact evidence." Earth-Science Reviews 218, 103677 (July 2021).
7. Pinter, N., Scott, A.C., Daulton, T.L., Podoll, A., Koeberl, C., Anderson, R.S., and Ishman, S.E. "The Younger Dryas impact hypothesis: A requiem." Earth-Science Reviews 106, 247–264 (2011).
8. Kerr, R.A. "Mammoth-killer impact rejected." Science 327, 1326 (2010); and Kerr, R.A., "Yes or no? Researchers can't agree if comet hit Earth 13,000 years ago." Science 343, 1190 (2014).
9. Holliday, V.T., Surovell, T., Meltzer, D.J., et al. "The Younger Dryas impact hypothesis: a cosmic catastrophe." Journal of Quaternary Science 29, 515–530 (2014); and subsequent Holliday et al. 2023 update in Earth-Science Reviews.
10. Buchanan, B., Collard, M., and Edinborough, K. "Paleoindian demography and the extraterrestrial impact hypothesis." Proceedings of the National Academy of Sciences 105, 11651–11654 (2008).
11. Israde-Alcántara, I., Bischoff, J.L., Domínguez-Vazquez, G., et al. "Evidence from central Mexico supporting the Younger Dryas extraterrestrial impact hypothesis." Proceedings of the National Academy of Sciences 109(13), E738–E747 (2012).
12. Moore, A.M.T., Kennett, J.P., Napier, W.M., Bunch, T.E., et al. "Evidence of cosmic impact at Abu Hureyra, Syria at the Younger Dryas onset (~12.8 ka): high-temperature melting at >2200°C." Scientific Reports 10, 4185 (2020).
13. Sun, N., et al. "Platinum and other trace element peaks in Hall's Cave, Texas, near the Younger Dryas onset." Scientific Reports, 2020.
14. Kjaer, K.H., Larsen, N.K., et al. "A large impact crater beneath Hiawatha Glacier in northwest Greenland." Science Advances 4 (2018). And subsequent Kenny et al. (2022) dating to ~58 Ma.
15. Hancock, Graham. Magicians of the Gods. Coronet, 2015; America Before, St. Martin's, 2019; Netflix series Ancient Apocalypse, seasons 1 (2022) and 2 (2024).