EXTINCTIONS VS Possible Impact Relationship
by: Charles O’Dale
Also see: Crater Impact Age vs Epoch
- 1. INTRODUCTION
- 2. EXTINCTIONS:
- ~12,000 years – YOUNGER DRYAS (YD) EXTINCTION;
- 33.9 Ma – EOCENE-OLIGOCENE EXTINCTION;
- 66.043 ±0.011 mA – CRETACEOUS-PALEOGENE EXTINCTION;
- 201.3 Ma – TRIASSIC-JURASSIC EXTINCTION;
- ~214 Ma – LATE TRIASSIC EXTINCTION (extinction at the Carnian/Norian boundary – 227 Ma);
- 252.28 Ma – PERMIAN-TRIASSIC EXTINCTION;
- ~374 Ma – LATE DEVONIAN EXTINCTION; and
- ~450 Ma – ORDOVICIAN EXTINCTION.
- 3. GEOLOGICAL PERIODS VS IMPACTS
- 4. REFERENCE PAPERS
An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the amount of life on earth. Such an event is identified by a sharp change in the diversity and abundance of macroscopic life. It occurs when the rate of extinction increases with respect to the rate of speciation. Because the majority of diversity and biomass on Earth is microbial, and thus difficult to measure, recorded extinction events affect the easily observed, biologically complex component of the biosphere rather than the total diversity.
Over 98% of documented species are now extinct, but extinction occurs at an uneven rate. Based on the fossil record, the background rate of extinctions on Earth is about two to five taxonomic families of marine invertebrates and vertebrates every million years. Marine fossils are mostly used to measure extinction rates because of their superior fossil record and stratigraphic range compared to land organisms.
Since life began on Earth, several major mass extinctions have significantly exceeded the background extinction rate. In the past 540 million years there have been five major events when over 50% of animal species died. Mass extinctions seem to be a Phanerozoic phenomenon, with extinction rates low before large complex organisms arose. Estimates of the number of major mass extinctions in the last 540 million years range from as few as five to more than twenty. These differences stem from the threshold chosen for describing an extinction event as “major”, and the data chosen to measure past diversity.
The Cretaceous–Paleogene extinction event, which occurred approximately 66 million years ago (Ma), was a large-scale mass extinction of animal and plant species in a geologically short period of time. It is generally believed that the K-Pg extinction was triggered by a massive comet/asteroid impact and its catastrophic effects on the global environment, including a lingering impact winter that made it impossible for plants and plankton to carry out photosynthesis. Various other impacts might also be associated with extinction events.
Evidence that an impact event may have caused the Cretaceous–Paleogene extinction event has led to speculation that similar impacts may have been the cause of other extinction events, including the P–Tr extinction, and therefore to a search for evidence of impacts at the times of other extinctions and for large impact craters of the appropriate age. Below I have listed impact structures whose ages coincide with recorded extinctions. Evidence for a related impact, if any, is documented.
~12,000 years – YOUNGER DRYAS (YD) EXTINCTION
Approximately 13,000 years ago, the earth was emerging from a glacial period, with temperatures approaching modern levels in many areas. In the Younger Dryas (YD) period, suddenly that trend reversed with the planet entering a cooling period lasting 1,300 ± 70 years. During this period the Stone Age Clovis people became extinct along with 35 mammal and 19 bird genera. A thin layer of Black Mat sediment, (YD Boundary – YDB) with a signature of an extraterrestrial impact overlies Clovis-age sites across North America dated ~12.9 ka. Above the YDB containing geology younger than the YD, NO trace of the Clovis people or the extinct 35 mammal and 19 bird genera exist.
Black Mat The black organic-rich layer or ‘‘black mat’’ that bridges the Pleistocene-Holocene transition (last deglaciation), is in the form of mollic paleosols, aquolls, diatomites, or algal mats with radiocarbon ages suggesting they are stratigraphic manifestations of the Younger Dryas cooling episode 10,900 B.P. to 9,800 B.P. (radiocarbon years). This layer or mat covers the Clovis-age landscape or surface on which the last remnants of the terminal Pleistocene megafauna are recorded. Stratigraphically and chronologically the extinction appears to have been catastrophic, seemingly too sudden and extensive for either human predation or climate change to have been the primary cause. This sudden Rancholabrean termination at 10,900 ± 50 B.P. appears to have coincided with the sudden climatic switch from Allerød warming to Younger Dryas cooling (Haynes 2008).
Evidence for Impact:
A characteristic of the YD boundary is varying peak abundances of:
(i) magnetic grains with iridium;
(ii) magnetic microspherules;
(v) glass-like carbon containing nanodiamonds: In March 2012, researchers identified a nearly 13,000-year-old layer of thin, dark sediment buried in the floor of Lake Cuitzeo in central Mexico. A family of nanodiamonds, including the impact form of nanodiamonds called lonsdaleite*, Lonsdaleite is unique to cosmic impacts and is conclusively identified within this YD layer.
*Lonsdaleite (named in honour of Kathleen Lonsdale), also called hexagonal diamond in reference to the crystal structure, is an allotrope of carbon with a hexagonal lattice. In nature, it forms when meteorites containing graphite strike the Earth. The great heat and stress of the impact transforms the graphite into diamond, but retains graphite’s hexagonal crystal lattice. Lonsdaleite was first identified in 1967 from the Canyon Diablo meteorite, where it occurs as microscopic crystals associated with diamond.
(vi) carbon spherules: The researchers also found spherules that had collided at high velocities with other spherules during the chaos of impact. Such features could not have formed through anthropogenic, volcanic, or other natural terrestrial processes (Israde-Alcántaraa 2012).
The following impacts “may” be related to the Younger Dryas Extinction:
Included are craters in Northern Quebec/Labrador (labeled as “un-detected ice impacts?”).
Based on current data, the following is a preliminary model for formation of the YDB. A comet or asteroid, possibly a previously fragmented object that was once greater than several hundred meters in diameter, entered the atmosphere at a relatively shallow angle (>5° and<30°). Thermal radiation from the air shock reaching Earth’s surface was intense enough to pyrolyze biomass and melt silicate minerals below the flight path of the impactor. Pyrolytic products were oxidized, locally depleting the atmosphere of oxygen, and within microseconds, residual free carbon condensed into diamond-like crystal structures, carbon spherules, carbon onions, and aciniform soot. This involved a carbon vapor deposition like process similar to diamond-formation during TNT detonation. In some cases, carbon onions grew around the nanodiamonds and other nanomaterials. At the same time, iron-rich and silicate materials may have melted to form magnetic spherules. Several seconds later, depending on the height of the thermal radiation source, the air shock arrived. Nanodiamonds, magnetic spherules, carbon spherules, and other markers were lofted by the shock-heated air into the upper atmosphere, where prevailing winds distributed them across the Northern and Southern Hemispheres. We suggest that the above model can account for the observed YDB markers (Israde-Alcántaraa et al, 2012).
Grieve R.A.F., Robertson P.B., IMPACT STRUCTURES IN CANADA, the Journal of the Royal Astronomical Society of Canada, February 1975
Kraus et al, Nanosecond formation of diamond and lonsdaleite by shock compression of graphite, Nature Communications 7, Article number: 10970 14 March 2016
Meen V.B., MEREWETHER CRATER – A POSSIBLE METEORITE CRATER,the Proceedings of the Geological Association Canada 1957 pp 49-67. (unless otherwise noted, the Merewether data quoted above is from this paper).
Ian SPOONER, George STEVENS, Jared MORROW, Peir PUFAHL, Richard GRIEVE, Rob RAESIDE, Jean PILON, Cliff STANLEY, Sandra BARR, and David MCMULLIN, Identification of the Bloody Creek structure, a possible impact crater in southwestern Nova Scotia, Canada. Meteoritics & Planetary Science 44, Nr 8, 1193–1202 (2009)
Haynes, C. V., Younger Dryas ‘‘black mats’’ and the Rancholabrean termination in North America Departments of Anthropology and Geosciences, Arizona, January 23, 2008.
Isabel Israde-Alcántara, James L. Bischoff, Gabriela Domínguez-Vázquez, Hong-Chun Li, Paul S. DeCarli, Ted E. Bunch, James H. Wittke, James C. Weaver, Richard B. Firestone, Allen West, James P. Kennett, Chris Mercer, Sujing Xie, Eric K. Richman, Charles R. Kinzie, and Wendy S. Wolbach, Evidence from central Mexico supporting the Younger Dryas extraterrestrial impact hypothesis, University of Hawaii, Honolulu, HI, January 31, 2012
Kinzie et al, 2014 Nanodiamond-Rich Layer across Three Continents Consistent with Major Cosmic Impact at 12,800 Cal BP. The Journal of Geology, 2014, volume 122.
Nicholas Pintera, Andrew C. Scottb, Tyrone L. Daultonc, Andrew Podolla, Christian Koeberld, R. Scott Andersone, Scott E. Ishmana, The Younger Dryas impact hypothesis: A requiem, Earth-Science Reviews, Volume 106, June 2011
Zamora, A. Solving the Mystery of the Carolina Bays
Younger Dryas Extinction Impact Related? (Bloody Creek @ 29:30).
33.9 Ma – EOCENE-OLIGOCENE EXTINCTION
The following impacts “may” be related to the Eocene-Oligocene Extinction:
|CRATER||DIA (km)||AGE (Ma)|
|Popigai, Russia||90||35.7 ± 0.2|
|Chesapeake, Virginia||40||35.5 ± 4|
|Mistastin||28||36.4 ± 4|
|Wanapitei||3 to 7.5||37.2 ± 1.2|
The 33.9 Ma transition between the end of the Eocene and the beginning of the Oligocene, called the Grande Coupure (the “Great Break” in continuity) in Europe, is marked by large-scale extinction and floral and faunal turnover (although minor in comparison to the largest mass extinctions). Most of the affected organisms were marine or aquatic in nature. They included the last of the ancient cetaceans, the Archaeoceti. This was a time of major climatic change, especially cooling, not obviously linked with any single major impact or any major volcanic event. One cause of the extinction event is speculated to be volcanic activity. Another speculation is that the extinctions are related to several meteorite impacts that occurred about this time. One such event happened near present-day Chesapeake Bay, and another the Popigai crater of central Siberia, scattering debris perhaps as far as Europe. The leading scientific theory on climate cooling at this time is decrease in atmospheric carbon dioxide, which slowly declined in the mid to late Eocene and possibly reached some threshold approximately 34 million years ago. This boundary is closely linked with the Oligocene Oi-1 event, an oxygen isotope excursion that marks the beginning of ice sheet coverage on Antarctica (Wikipedia).
Evidence for Impact: “The late Eocene probably experienced multiple impact events. There are two large impact craters; the 90 km Chesapeake Bay and the 100 km Popigai structures. There are also at least two spherule deposits; the North American (N.A.) microtektites and the slightly older clinopyroxene-bearing (cpx) spherules. Isotopic data are consistent with the N.A. microtektites being derived from the Chesapeake Bay impact and the cpx spherules being derived from the Popigai impact. The late Eocene is also characterized by a 2.5 m.y. anomaly in the flux of 3He that is interpreted to be caused by an increased flux of interplanetary dust, due to a comet shower that may be responsible for all these phenomena.” (Kyte et al, 2002)
“Two impacts (Popigai & Chesapeake) — the two biggest in the past 65 million years, and among the biggest of all time — struck Earth with a sudden double punch that might even have been simultaneous. Impacts this size are so rare that the timing was almost certainly no coincidence; perhaps a pair of gravitationally bound asteroids happened to cross Earth’s path. Both impacts seem to have made themselves felt around the world: the Popigai impact was most likely responsible for layers of debris that were dug up in the 1980s in Italy, while the Chesapeake crater is probably responsible for bits of quartz scattered from Georgia to Barbados” (Zimmer, 1998).
F. T. Kyte and S. Liu. IRIDIUM AND SPHERULES IN LATE EOCENE IMPACT DEPOSITS. Lunar and Planetary Science XXXIII (2002)
Carl Zimmer. CRATERS WITHOUT IMPACT DISCOVER Vol. 19 No. 01, January 1998
66.043 ±0.011 mA – CRETACEOUS-PALEOGENE EXTINCTION
76% of all species lost — Ammonite 15 cm length
The delicate leafy sutures decorating this shell represent some advanced engineering, providing the fortification the squid-like ammonite required to withstand the pressure of deep dives in pursuit of its prey. Dinosaurs may have ruled the land during the Cretaceous period but the oceans belonged to the ammonites. But volcanic activity and climate change already placed the ammonites under stress. The asteroid impact that ended the dinosaurs’ reign provided the final blow. Only a few dwindling species of ammonites survived. Today, the ammonites’ oldest surviving relative is the nautilus. Will it survive the sixth great extinction?
CRETACEOUS-TERTIARY/CRETACEOUS-PALEOGENE (K–Pg) BOUNDARY
A major stratigraphic boudary on Earth marking the end of the Mesozoic Era, best known as the age of the dinosaurs. The boundary is defined by a global extinction event that caused the abrupt demise of the majority of all life on Earth. It has been dated to 65 million years ago, coeval with the age of the 200-kilometer-diameter Chicxulub impact structure in Mexico.
K/T Boundary: concentrations of the rare platinum group elements (PGEs; Ru, Rh, Pb, Os, Ir, and Pt) and other siderophile elements (e.g., Co, Ni) are enriched by up to 4 orders of magnitude in the thin clay layer marking the K-T boundary compared to those of normal terrestrial crustal rocks. Cretacious/Tertiary boundary (the C abbreviation is already assigned to the Cambrian system), at present practically synonymous with marking the giant mass extinction 65 Ma ago. The extinction of the dinosaurs at that time is only a subordinate part of this remarkable event. See Chicxulub impact structure.
The following impacts occurred around the time of the Cretaceous-Paleogene Extinction:
|CRATER||DIA (km)||AGE (Ma)|
|Chicxulub, Yucatan, Mexico||150||66.043 ±0.011|
|Eagle Butte, Alberta||10||<65|
|Maple Creek, Saskatchewan||6||<75|
The Cretaceous–Paleogene (K–Pg) extinction event, also known as the Cretaceous–Tertiary (K–T) extinction, was a mass extinction of some three-quarters of the plant and animal species on Earth—including all non-avian dinosaurs—that occurred over a geologically short period of time approximately 66 million years ago. With the exception of some ectothermic species in aquatic ecosystems like the leatherback sea turtle and crocodiles, no tetrapods weighing more than 55 pounds (25 kilos) survived. It marked the end of the Cretaceous period and with it, the entire Mesozoic Era, opening the Cenozoic Era that continues today.
In the geologic record, the K–Pg event is marked by a thin layer of sediment called the K–Pg boundary, which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows high levels of the metal iridium, which is rare in the Earth’s crust but abundant in asteroids.
Evidence for impact Sedimentary layers found all over the world at the Cretaceous–Paleogene boundary contain a concentration of iridium many times greater than normal. Iridium is extremely rare in Earth’s crust because it is a siderophile element, and therefore most of it traveled with the iron as it sank into Earth’s core during planetary differentiation. Iridium is abundant in most asteroids and comets suggesting that an asteroid struck the Earth at the time of the K–Pg boundary. There were earlier speculations on the possibility of an impact event, but this was the first hard evidence of an impact.
In a 2013 paper, Paul Renne of the Berkeley Geochronology Center reported that the date of the asteroid event is 66.043±0.011 million years ago, based on argon–argon dating. He further posits that the mass extinction occurred within 32 thousand years of this date.
Renne, Paul R.; (et al) Jan (7 February 2013). “Time Scales of Critical Events Around the Cretaceous-Paleogene Boundary”. Science 339 (6120)
Extraterrestrial cause for the cretaceous–tertiary extinction. (1980 – preChicxulub discovery)
201.3 Ma – TRIASSIC-JURASSIC EXTINCTION
The following impacts “may” be related to the Triassic–Jurassic Extinction:
|CRATER||DIA (km)||AGE (Ma)|
|Red Wing||9.1||200 ± 25|
|Viewfield||2.5||190 ± 20|
The Triassic–Jurassic extinction event marks the boundary between the Triassic and Jurassic periods, 201.3 million years ago, and is one of the major extinction events of the Phanerozoic eon, profoundly affecting life on land and in the oceans. In the seas a whole class (conodonts) and twenty percent of all marine families disappeared. On land, all large crurotarsans (non-dinosaurian archosaurs) other than crocodilians, some remaining therapsids, and many of the large amphibians were wiped out. At least half of the species now known to have been living on Earth at that time went extinct. This event vacated terrestrial ecological niches, allowing the dinosaurs to assume the dominant roles in the Jurassic period. This event happened in less than 10,000 years and occurred just before Pangaea started to break apart. In the area of Tübingen (Germany), a Triassic-Jurassic bonebed can be found, which is characteristic for this boundary. Statistical analysis of marine losses at this time suggests that the decrease in diversity was caused more by a decrease in speciation than by an increase in extinctions (Wikipedia).
Evidence for Impact: “Analysis of tetrapod footprints and skeletal material from more than 70 localities in eastern North America shows that large theropod dinosaurs appeared less than 10,000 years after the Triassic-Jurassic boundary and less than 30,000 years after the last Triassic taxa, synchronous with a terrestrial mass extinction. This extraordinary turnover is associated with an iridium anomaly (up to 285 parts per trillion, with an average maximum of 141 parts per trillion) and a fern spore spike, suggesting that a bolide impact was the cause. Eastern North American dinosaurian diversity reached a stable maximum less than 100,000 years after the boundary, marking the establishment of dinosaur-dominated communities that prevailed for the next 135 million years” (Olsen et al 2002).
P. E. Olsen, D. V. Kent, H.-D. Sues, C. Koeberl, H. Huber, A. Montanari, E. C. Rainforth, S. J. Fowell, M. J. Szajna, B. W. Hartline ASCENT OF DINOSAURS LINKED TO AN IRIDIUM ANOMALY AT THE TRIASSIC JURASSIC BOUNDARY Science, 17 May 2002
~214 Ma – LATE TRIASSIC EXTINCTION
80% of species lost — Conodont teeth 1 mm
Palaeontologists were baffled about the origin of these toothy fragments, mistaking them for bits of clams or sponges. But the discovery of an intact fossil in Scotland in the 1980s finally revealed their owner – a jawless eel-like vertebrate named the conodont which boasted this remarkable set of teeth lining its mouth and throat. They were one of the first structures built from hydroxyapatite, a calcium-rich mineral that remains a key component of our own bones and teeth today. Of all the great extinctions, the one that ended the Triassic is the most enigmatic. No clear cause has been found.
Scientists reported in the journal Nature today (March 13, 1998) that they had found evidence of a chain of five craters formed 214 million years ago that was likely due to pieces of a comet crashing into the Earth’s surface, similar to the Comet Shoemaker-Levy 9 impact on Jupiter in 1994. The craters no longer appear to be in a straight line due the shifting of the Earth’s continents due to plate tectonics. Two of the craters, Manicouagan and Saint Martin, are in Canada (Quebec and Manitoba, respectively). The other three craters are Rochechouart in Europe, Obolon in the Ukraine and Red Wing in Minnesota. The impacts appeared to occur at the Norian stage of the Triassic period, about six million years after a mass extinction that wiped out 80% of all the species on Earth, but the ages of all the craters are uncertain enough to include this extinction (from ScienceWeb Daily).
The 34-million-year (My) interval of the Late Triassic is marked by the formation of several large impact structures on Earth. Late Triassic impact events have been considered a factor in biotic extinction events in the Late Triassic (e.g., end-Triassic extinction event), but this scenario remains controversial because of a lack of stratigraphic records of ejecta deposits. Here, we report evidence for an impact event (platinum group elements anomaly with nickel-rich magnetite and microspherules) from the middle Norian (Upper Triassic) deep-sea sediment in Japan. This includes anomalously high abundances of iridium, up to 41.5 parts per billion (ppb), in the ejecta deposit, which suggests that the iridiumenriched ejecta layers of the Late Triassic may be found on a global scale. The ejecta deposit is constrained by microfossils that suggest correlation with the 215.5-Mya, 100-km-wide Manicouagan impact crater in Canada. Our analysis of radiolarians shows no evidence of a mass extinction event across the impact event horizon, and no contemporaneous faunal turnover is seen in other marine planktons. However, such an event has been reported among marine faunas and terrestrial tetrapods and floras in North America. We, therefore, suggest that the Manicouagan impact triggered the extinction of terrestrial and marine organisms near the impact site but not within the pelagic marine realm (Onoue, Tetsuji, October 2012).
Summary of impact structures in the Late Triassic.
|The following impacts “may” be related to the Late Triassic Extinction:
Did the Manicouagan impact trigger end-of-Triassic mass extinction?
J. P. Hodych, G. R. Dunning
We use U-Pb zircon dating to test whether the bolide impact that created the Manicouagan crater of Quebec also triggered mass extinction at the Triassic/Jurassic boundary. The age of the impact is provided by zircons from the impact melt rock on the crater floor; we show that the zircons yield a U-Pb age of 214 ±1 Ma. The age of the Triassic/Jurassic boundary is provided by zircons from the North Mountain Basalt of the Newark Supergroup of Nova Scotia; the zircons yield a U-Pb age of 202 ±1 Ma. This should be the age of the end-of-Triassic mass extinction that paleontology and sedimentation rates suggest occurred less than 1 m.y. before extrusion of the North Mountain Basalt. Although the Manicouagan impact could thus not have triggered the mass extinction at the Triassic/Jurassic boundary (impact likely having preceded extinction by 12 ±2 m.y.), the impact may possibly have triggered an earlier mass extinction at the Carnian/Norian boundary – 227Ma, in the Late Triassic. (Geology (1992)
The Triassic-Jurassic Extinction – Volcanic?
The end-Triassic mass extinction, with more than 50% genus loss in both marine and continental realms, is one of the five periods of major biodiversity loss in Earth’s history and provides an eminent case history of global biosphere turnover. Massive volcanism through largescale flood basalt eruptions is the favoured terrestrial culprit. The end-Triassic is marked by Large Igneous Province (LIP) emplacement of the Central Atlantic Magmatic Province (CAMP). Deenen et al, 2009.
Boyle, D.R. et al, Geochemistry, geology, and isotopic (Sr, S, and B) composition of evaporites in the Lake St. Martin impact structure: New constraints on the age of melt rock formation,GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, VOL. 8, 2007.
M.H.L. Deenen, M. Ruhl, N.R. Bonis,W. Krijgsman, W.M. Kuerschner, M. Reitsma, M.J. van Bergen, A new chronology for the end-Triassic mass extinction. Earth and Planetary Science Letters 2009.
Donofrio, R.R., North American impact structures hold giant field potential. Oil and Gas Journal, 1998.
Donofrio, R.R.: Impact Craters: Implications for Basement Hydrocarbon Production. Journal of Petroleum Geology, 1981.
Grieve, R.A.F., Impact structures in Canada, Geological Association of Canada, no. 5, 2006.
Robertson, P.B., Grieve, R.A.F., Impact Structures in Canada: their recognition and characteristics. The Journal of the Royal Astronomical Society, February 1975.
Smith, R. Dark days of the Triassic: Lost world – Did a giant impact 200 million years ago trigger a mass extinction and pave the way for the dinosaurs? NATURE 17 Nov. Vol#479 2011.
Tetsuji Onouea, et al; Deep-sea record of impact apparently unrelated to mass extinction in the Late Triassic. Rutgers University/Lamont-Doherty Earth Observatory, Palisades, NY, October 3, 2012
252.28 Ma – PERMIAN-TRIASSIC EXTINCTION
96% of species lost — Tabulate coral, 5 CM
Known as “the great dying”, this was by far the worst extinction event ever seen; it nearly ended life on Earth. The tabulate corals were lost in this period – today’s corals are an entirely different group. What caused it? A perfect storm of natural catastrophes. A cataclysmic eruption near Siberia blasted CO2 into the atmosphere. Methanogenic bacteria responded by belching out methane, a potent greenhouse gas. Global temperatures surged while oceans acidified and stagnated, belching poisonous hydrogen sulfide. “It set life back 300 million years,” says Schmidt. Rocks after this period record no coral reefs or coal deposits.
The following impact “may” be related to the Permian–Triassic (P–Tr) extinction event:
The Permian–Triassic (P–Tr) extinction event, informally known as the Great Dying, was an extinction event that occurred 252.28 Ma (million years) ago, forming the boundary between the Permian and Triassic geologic periods, as well as the Paleozoic and Mesozoic eras. It is the Earth’s most severe known extinction event, with up to 96% of all marine species and 70% of terrestrial vertebrate species becoming extinct. It is the only known mass extinction of insects. Some 57% of all families and 83% of all genera became extinct. Because so much biodiversity was lost, the recovery of life on Earth took significantly longer than after any other extinction event, possibly up to 10 million years (Wikipedia).
Evidence for Impact: Reported evidence for an impact event from the P–Tr boundary level includes rare grains of shocked quartz in Australia and Antarctica; fullerenes trapping extraterrestrial noble gases; meteorite fragments in Antarctica; and grains rich in iron, nickel and silicon, which may have been created by an impact. However, the accuracy of most of these claims has been challenged. Quartz from Graphite Peak in Antarctica, for example, once considered “shocked”, has been re-examined by optical and transmission electron microscopy. The observed features were concluded to be not due to shock, but rather to plastic deformation, consistent with formation in a tectonic environment such as volcanism. An impact crater on the seafloor would be a possible cause of the P–Tr extinction, and such a crater would by now have disappeared. As 70% of the Earth’s surface is sea, an asteroid or comet fragment is more than twice as likely to hit ocean as it is to hit land. However, Earth has no ocean-floor crust more than 200 million years old, because the “conveyor belt” process of seafloor spreading and subduction destroys it within that time. Craters produced by very large impacts may be masked by extensive flood basalting from below after the crust is punctured or weakened. Subduction should not, however, be entirely accepted as an explanation of why no firm evidence can be found: as with the K-T event, an ejecta blanket stratum rich in siderophilic elements (e.g., iridium) would be expected to be seen in formations from the time. One attraction of large impact theories is that theoretically they could trigger other cause-considered extinction-paralleling phenomena, such as the Siberian Traps eruptions as being either an impact site or the antipode of an impact site. The abruptness of an impact also explains why more species did not rapidly evolve to survive, as would be expected if the Permian-Triassic event had been slower and less global than a meteorite impact (Wikipedia).
~374 Ma – LATE DEVONIAN EXTINCTION
75% of species lost — Trilobite, 5 cm length
Trilobites were the most diverse and abundant of the animals that appeared in the Cambrian explosion 550 million years ago. Their great success was helped by their spiky armour and multifaceted eyes. They survived the first great extinction but were nearly wiped out in the second. The likely culprit was the newly evolved land plants that emerged, covering the planet during the Devonian period. Their deep roots stirred up the earth, releasing nutrients into the ocean. This might have triggered algal blooms which sucked oxygen out of the water, suffocating bottom dwellers like the trilobites.
The following impacts “may” be related to the Late Devonian Extinction:
THE LATE DEVONIAN MASS EXTINCTION EVENT
The Devonian extinction had severe global effects. With a worldwide loss of 60% of existing taxa, every ecosystem was affected. Reef systems were forever changed with the massive deaths of stromatoporoids and tabulate corals. Brachiopods lost their stronghold as the dominant shelled marine invertebrate. Entire classes, such as the agnathan fishes, went extinct. From the loss of microscopic plankton to terrestrial plants, all life on Earth was affected by this major extinction event.
Asteroid impacts have become a popular theory examined at extinction events. McLaren (1970) proposed the first bolide-induced extinction for the Late Devonian. To be a single impact, studies have shown that the asteroid would need a diameter greater than ten kilometers. If an asteroid of those proportions impacted earth, it would kill life in the target area, generate earthquakes, tsunamis, wildfires and ballistic molten debris. Tsunamis, especially, would affect shallow marine ecosystems. The blast would heat the atmosphere sufficiently so that nitrogen could combine with oxygen to create nitric oxide and nitric acid. Rain falling in high concentrations could poison upper surface waters and destroy phytoplanktonic life. Calcareous shells would dissolve. Wildfires would produce dioxins and aromatic hydrocarbons, poisoning the environment. Significant addition of carbon dioxide into the atmosphere would create an icehouse effect. Global dust clouds could block sunlight, making photosynthesis impossible. Temperatures could drop below survivable ranges for many organisms.
Evidence for Impact: The Siljan Ring in Sweden, dated to the F-F boundary, has a diameter of 52 kilometers. Many craters have been studied for the Late Devonian extinction event (table), however the dates of many craters are either too wide to be accepted or dates too uncertain based on differing opinions. Larger craters might have been created in the ocean floor, but would now be destroyed by tectonics (McGhee, 1996). Others doubt a single asteroid impact could be responsible for such a severe extinction event.
McGhee GR Jr. 1996. The Late Devonian Mass Extinction. New York: Columbia University Press.
McLaren, D.J. 1970. Time, life and boundaries. Journal of Paleontology, 48,. 801–815.
~450 Ma – ORDOVICIAN EXTINCTION
86% of species lost — Graptolite 2-3 cm length
Graptolites, like most Ordovician life, were sea creatures. They were filter-feeding animals and colony builders. Their demise over about a million years was probably caused by a short, severe ice age that lowered sea levels, possibly triggered by the uplift of the Appalachians. The newly exposed silicate rock sucked CO2 out of the atmosphere, chilling the planet.
Jens Ormö, Erik Sturkell, Carl Alwmark & Jay Melosh
ABSTRACT: Approximately 470 million years ago one of the largest cosmic catastrophes occurred in our solar system since the accretion of the planets. A 200-km large asteroid was disrupted by a collision in the Main Asteroid Belt, which spawned fragments into Earth crossing orbits. This had tremendous consequences for the meteorite production and cratering rate during several millions of years following the event. The 7.5-km wide Lockne crater, central Sweden, is known to be a member of this family. We here provide evidence that Lockne and its nearby companion, the 0.7-km diameter, contemporaneous, Målingen crater, formed by the impact of a binary, presumably ‘rubble pile’ asteroid. This newly discovered crater doublet provides a unique reference for impacts by combined, and poorly consolidated projectiles, as well as for the development of binary asteroids.
Paleogeography of Baltica and neighboring cratons at the time of the increased cosmic bombardment following the ~470 Ma asteroid breakup event illustrating the resulting known craters (red dots). Clearwater East is dated to this event (~460–470 Ma). Light blue color represents areas of shallow epicontinental seas, and dark blue areas of deep ocean. This distribution may, however, have varied somewhat due to periodical transgressions and regressions of the sea. The timeline documents the related meteorite falls (black dot and line).
The following impacts “may” be related to the Ordovician Extinction:
The Ordovician–Silurian extinction event, the Ordovician extinction, was the second-largest of the five major extinction events in Earth’s history in terms of percentage of genera that went extinct and second largest overall in the overall loss of life. This was the second biggest extinction of marine life, ranking only below the Permian extinction. At the time, all known life was confined to the seas and oceans. More than 60% of marine invertebrates died including two-thirds of all brachiopod (hard upper/lower shells) and bryozoan (aquatic invertebrates) families.
Evidence for Impact: The Ordovician meteor event is a proposed shower of L chondrite meteors that occurred during the Middle Ordovician period, roughly 470 million years ago. This theory was proposed by Swiss and Swedish researchers based on the comparatively tight age clustering of L chondrite grains in sediments in southern Sweden. They proposed that a large asteroid transferred directly into a resonant orbit with Jupiter, which shifted its orbit to intercept Earth. In addition to the northern European evidence, there is circumstantial evidence that several Middle Ordovician meteors fell roughly simultaneously 469 million years ago in a line across North America, including the Decorah crater in Iowa, the Slate Islands crater in Lake Superior, and the Rock Elm crater in Wisconsin.
1. Heck, Philipp; Birger Schmitz, Heinrich Baur, Alex N. Halliday. Rainer Wieler (15). “Fast delivery of meteorites to Earth after a major asteroid collision”. Nature 430: 323-325.
2. H. Haack et al. Meteorite, asteroidal, and theoretical constraints on the 500-Ma disruption of the L chondrite parent body, Icarus, Vol. 119, p. 182 (1996).
3. Korochantseva et al. “L-chondrite asteroid breakup tied to Ordovician meteorite shower by multiple isochron 40Ar-39Ar dating” Meteoritics & Planetary Science 42, 1, pp. 3-150, Jan. 2007.
4. Vastag, Brian (18 February 2013). “Crater found in Iowa points to asteroid break-up 470 million years ago”. Washington Post. Retrieved 19 February 2013.
|PERIOD||NAME/PLACE||Age (million years)||Date Related Extinction||Notes|
|Orosirian||Vredefort, South Africa||1,970|
|Orosirian||Sudbury, Ontario, Canada||1,850||Sudbury Distal Ejecta|
|Ediacaran||Beaverhead, Idaho, USA||~600|
|Ediacaran||Kelly West, N.T., Australia||550|
|Ediacaran||Holleford, Ontario, Canada||550||Overflight of Holleford Crater|
|Cambrian||Presqu’ile , Quebec, Canada||<500||Geological dating|
|Ordovician||Carswell, Saskatchewan, Canada||485|
|Ordovician||Clearwater East, Quebec, Canada||~460–470|
|Ordovician||Pilot Lake, N.W.T. Canada||445||Ordovician|
|Silurian||Slate Islands, Ontario, Canada||436||Ordovician|
|Silurian||Rock Elm, Saskatchewan, Canada||420-440||Ordovician|
|Silurian||Lac Couture, Quebec, Canada||425|
|Devonian||Lac La Moinerie, Quebec, Canada||400||Late Devonian|
|Devonian||Brent, Ontario, Canada||396||Late Devonian||Overflight of Brent Crater|
|Devonian||Elbow, Saskatchewan, Canada||395||Late Devonian||Geological dating|
|Devonian||Flynn Creek, Tennessee, USA||360|
|Carboniferous||Charlevoix, Quebec, Canada||342||Late Devonian||Elevated Earthquake Zone|
|Carboniferous||Crooked Creek, Missouri, USA||320|
|Carboniferous||Middlesboro, Kentucky, USA||300|
|Carboniferous||Serpent Mound, Ohio, USA||300|
|Carboniferous||Ile Rouleau, Quebec, Canada||<300||Geological dating|
|Permian||Clearwater West, Quebec, Canada||290|
|Triassic||Gow, Saskatchewan, Canada||<250||Permian–Triassic (P–Tr) extinction event|
|Triassic||St. Martin, Manitoba, Canada||219||Late Triassic|
|Triassic||Manicouagan, Quebec, Canada||214||end-middle Norian|
|Jurassic||Red Wing, North Dakota, USA||200||Late Triassic/Triassic-Jurassic|
|Jurassic||Viewfield, Saskatchewan, Canada||190||Triassic-Jurassic|
|Jurassic||Upheaval Dome, Utah, USA||<170||Geological dating|
|Jurassic||Strangways, N.T., Australia||150|
|Cretaceous||Carswell, Saskatchewan, Canada||115|
|Cretaceous||Sierra Madre, Texas, USA||100|
|Cretaceous||West Hawk, Ontario, Canada||100||Geological dating|
|Cretaceous||Deep Bay, Saskatchewan, Canada||99||Geological dating|
|Cretaceous||Maple Creek, Saskatchewan, Canada||<75||Geological dating|
|Cretaceous||Chicxulub, Yucatan, Mexico||66.043 ±0.011||CRETACEOUS-PALEOGENE|
|Paleogene||Eagle Butte, Alberta, Canada||<65||Geological dating|
|Paleogene||Montagnais, Nova Scotia, Canada||50|
|Paleogene||Mistastin, Labrador, Canada||36|
|Paleogene||Wanapitei, Ontario, Canada||37|
|Neogene||Haughton Dome, N.W.T., Canada||15|
|Quaternary||Pingualuit, Quebec, Canada||1.4||Overflight of Pingualuit Crater|
|Quaternary||Barringer, Arizona, USA||0.049||Jointed|
|Quaternary||Whitecourt Alberta, Canada||0.00113|
Comparison of commonly used dating methods.
|Name of Method||Age range of Application||Material Dated||Methodology|
|Radiocarbon||1 – 70,000 years||Organic material such as bones, wood, charcoal, shells||Radioactive decay of 14C in organic matter after removal from bioshpere|
|K-Ar dating||1,000 – billion of years||Potassium-bearing minerals and glasses||Radioactive decay of 40K in rocks and minerals|
|Uranium-Lead||10,000 – billion of years||Uranium-bearing minerals||Radioactive decay of uranium to lead via two separate decay chains|
|Uranium series||1,000 – 500,000 years||Uranium-bearing minerals, corals, shells, teeth, CaCO3||Radioactive decay of 234U to 230Th|
|Fission track||1,000 – billion of years||Uranium-bearing minerals and glasses||Measurement of damage tracks in glass and minerals from the radioactive decay of 238U|
|Luminescence (optically or thermally stimulated)||1,000 – 1,000,000 years||Quartz, feldspar, stone tools, pottery||Burial or heating age based on the accumulation of radiation-induced damage to electron sitting in mineral lattices|
|Cosmogenic Nuclides||1,000 – 5,000,000 years||Typically quartz or olivine from volcanic or sedimentary rocks||Radioactive decay of cosmic-ray generated nuclides in surficial environments|
|Magnetostratigraphy||20,000 – billion of years||Sedimentary and volcanic rocks||Measurement of ancient polarity of the earth’s magnetic field recorded in a stratigraphic succession|
|Tephrochronology||100 – billions of years||Volcanic ejecta||Uses chemistry and age of volcanic deposits to establish links between distant stratigraphic successions|