MANICOUAGAN IMPACT STRUCTURE
by: Charles O’Dale
- Type: Peak ring basin
- Age (ma): 214 ± 1a – TRIASSIC
- Diameter: 100 km
- Location: Quebec, Canada. N 51° 23′ W 68° 42′
- Shock Metamorphism: Shatter cones rarely well-developed (Murtagh, 1976; 1972). PDF in plagioclase, quartz grains, K-feldspar, and other minerals. Maskelyniteb.
a Dating Method: K-Ar, Rb-Sr, U-Pb. U-Pb on zircons (Hodych & dunning, 1992). Triassic age confirmed by Rb-Sr mineral isochron with age of 214 +/- 5 Ma for melt rock (Jahn et al., 1978) and by Ar-Ar and K-Ar ages.
b Maskelynite: A type of naturally occurring glass having the composition of plagioclase series feldspar, created by the vitrification of plagioclase by shock melting in meteorites and meteorite impacts. (Dence et al 1967)
- Late Triassic extinction event;
- Stratigraphic record in the Fundy Rift Basin;
- Manicouagan Impact ejecta;
- Aerial Exploration;
- Ground Exploration;
EARTH SCIENCE PICTURE OF THE DAY
Conference: 53rd Annual GSA Northeastern Section Meeting – 2018
Lawrence H Tanner, Michael J. Clutson, David E. Brown
3. STRATIGRAPHIC RECORD IN THE FUNDY RIFT BASIN OF THE MANICOUAGAN IMPACT: BOLIDE WITH A BANG OR A WHIMPER?
The terrestrial redbeds of the Blomidon Formation were deposited in the Fundy rift basin during Norian to Hettangian time. A 10-m-thick zone of intensely deformed strata that occurs near the base of the formation is characterized by rubblization and step-wise faulting. Correlation of this zone basin-wide indicates that it is a record of a very powerful paleoseismic event. The greater thickness of the deformed zone in proximity to the border fault, the Minas Fault Zone (MFZ), indicates that movement of the MFZ was the immediate cause of this paleoseismicity. The presence in strata just above the deformed zone of quartz grains displaying features of shock metamorphism raises the intriguing possibility that reactivation of the MFZ was triggered by a bolide impact. (Tanner 2002)
The ~100 km-wide Manicouagan impact structure in northeastern Canada, 700 km from the Fundy rift basin, is one of the largest well-documented impact sites. Once considered a candidate for the cause of the end-of-Triassic extinctions, U-Pb zircon dating of the impact melt establishes the age of the impact as much earlier Norian, approximately coeval with the seismic deformation of the Blomidon Formation. Stratigraphic constraint of the age of the impact allows an accurate assessment of the effects of this event on biota. (see – David E. Brown ET AL 2018 and Onoue 2012 above)The impact did trigger a powerful seismic event as Lawrence Tanner from Bloomsburg University recently discovered in a deformed zone of the Fundy Rift Basin. “There have been previous reports attempting to link paleoseismicity, as recorded by soft-sediment deformation features, to impacts,” Tanner explained. “But this is the first instance of linking the Manicouagan impact to the stratigraphic record. I made the association between the impact and paleoseismicity in the Fundy Rift Basin, a sedimentary basin 700 km away from the impact site, and went looking for shocked quartz grains. Finding them allows us to place this impact into a stratigraphic context and look elsewhere to see if there are any significant biotic effects. So far, there don’t seem to be any.” The Fundy rift Basin experienced a substantial period of volcanic activity at the time of the Manicouagan impact. (GEOLOGICAL SOCIETY OF AMERICA 2002)
4. MANICOUAGAN IMPACT EJECTA
The fireball generated by the impact probably expanded as far as the present location of New York City. The impact also triggered powerful seismic events and ejected material out of the atmosphere. The ejected material was sent on a ballistic trajectory around the earth. Like the Chicxulub impact, the Manicouagan impact left behind a global geochemical signature in the rock record.
As a result of the Manicouagan impact, molten rock and dust from this bedrock left a thin layer of glass beads and shattered mineral grains in a rock deposit in the United Kingdom.
Dating of this UK deposit connected it to Manicouagan precluding most of the European impact sites nearby as the source of the deposit layer.
Walkden, Kelley, Parker, Thackrey (2006),
European Space Agency: [SELECTED QUOTES]The documented late Triassic spherule layer of SW England deposit (illustrated here) contains an abundance of spherules, common shocked quartz and a suite of accessory minerals believed to have been derived direct from the impact site. These include garnets, ilmenites, zircons and biotites. Garnets and ilmenites are highly fractured, and biotites show prominent kink bands indicative of shock.
The time of the deposit was determined by noting the decay of radioactive potassium in the spherule layer and dates at 214 ± 2.5Ma. This is comfortably within the date of the late Triassic Manicouagan impact event.
Single grain K-Ar ages for the biotites are in the range 700-1100Ma which are superficially similar to the Grenville rocks around the Manicouagan impact site. Given the geometry of the contemporaneous Triassic continental assembly, the contact point of the impactor was only 20 crater diameters from the site of deposition of this ejecta layer. (Thackrey et al 2006) [SELECTED QUOTES]
A distal impact deposit has recently been reported from a location near Bristol, England. The 0-15 cm thick, discontinuous layer is of Late Triassic age and occurs in a sequence of red calcareous mudstones deposited unconformably on Carboniferous limestone, in a semi-arid, continental environment. It consists of closely packed, millimetre sized green spherules, composed of a green clay surrounding a calcitic or hollow core. They have been inferred to be diagenetically altered type I spherules, formed from quenched impact-melt droplets, deposited aerially from an expanding impact ejecta curtain. The stratum, with a reported 39Ar – 40Ar age of approximately 214 Ma, is coincident with the age of two known impact craters from the Late Triassic, Manicouagan in Canada and Rochechouart in France. The focus of the present study is to determine if a meteoritic component and projectile type can be identified from this impactoclastic air-fall bed and adjacent strata, using a combination of geochemical analyses – chromium isotope systematics, siderophile and platinum group elemental ratios. In particular, we have developed a new method for the isolation and concentration of chromium, following sample dissolution. Chromium isotope ratios are determined using a multiple collector, inductively coupled plasma, mass spectrometer (MC-ICP-MS) for which the conditions have been established to obtain high precision ratio measurements. ( AMORet al 2005)
The Manicouagan impact crater is one of the largest impact structures still preserved on the surface of the Earth and is classified as a complex meteorite crater. The annular moat, prominent in space images, fills a ring where impact-brecciated rock was once eroded away by glaciation. The diameter of the original crater was approximately three times the size of the circular lake taken from the space shuttle (above). Erosion has removed about a kilometre of rock from the region. The inner plateau remaining in the center of the annular moat is made up of metamorphic and igneous rock types along with melt sheet and is not as susceptible to glacial erosion.
Approximately 214 million years ago an estimated 10 kilometre wide hypervelocity meteorite impacted at between 12 and 30 kilometres per second and formed the Manicouagan Impact Crater. The resultant 100 kilometre diameter Manicouagan crater is one of the largest impact craters still preserved on the surface of our planet. For comparison, the Copernicus crater on the moon has a diameter of 93 kilometres and the annular moat of the Manicouagan structure would fit comfortably within the rim of this lunar crater.
Morphological elements of the Manicouagan structure are based on topographical expression and are:
- outer circumferential depression – ~150-km outer diameter;
- outer disturbed zone – ~150 km diameter;
- inner fractured zone – ~100 km outer diameter;
- annular moat – ~65 km outer diameter;
- inner plateau – ~55 km outer diameter;
- central region – ~25 km outer diameter. (Grieve, Head 1983)
Outer Circumferential Depression, Outer Disturbed Zone and Inner Fractured Zone
Peripheral Trough (annular moat)
The water filled circular annular moat that is prominent in space images is only one third of the size of the original crater. The water in the annular moat fills a ring where impact-brecciated rock was eroded away by glaciation. Before flooding of the reservoir, isolated outcrops of tilted and deformed limestone, siltstone and shale were found on the inner edges of the moat (Murtaugh, 1975). This rock formation (RIGHT) is found at the extreme eastern portion of the annular moat on one of the small islands. Note the rock structure is breccia free gneiss. The central peak of the structure is visible over 10 km in the distance.
The Inner Plateau of the Manicouagan structure is bounded by the annular moat, overlain by melt sheet, underlain by shocked basement rock (Orphal, Schultz 1978). We found a “lunar landscape” here containing various breccia types. The astronauts exploring the moon found that impact-melt breccias, similar to what we found here, were the most common rock types at the Apollo highland sites (Apollos 14, 15, 16 and 17) (Haskin 1998). We documented impact breccias formed by similar and very different country rocks like those found on the moon!
The Central Region of the Manicouagan Structure is a complex zone of uplifted, shocked and metamorphosed basement rocks with small tabular bodies of impact melt and pseudotachylite veins (Orphal, Schultz 1978). Recent U-Pb zircon dating of the impact melt gave an age of 214 ± 1 million years.
The red dot represents the approximate area of the Manicouagan impact 214 million years ago in the Triassic Period. The meteorite responsible for the Manicouagan crater struck in the beginning of the Mesozoic era in the Triassic period. In that time the world climate was in a warming phase and becoming relatively dry. The continental plates, joined about 200 million years prior to this, began to break into continents. Fewer species existed than today but survived in high populations. The first dinosaurs, and possibly the first mammals, evolve. It is suggested that the Manicouagan impact triggered the extinction of terrestrial and marine organisms near the impact site but not in an open sea.
6. Aerial Exploration
The water filled circular annular moat that is prominent in space images and illustrated here from GOZooM, is only one third of the size of the original crater. This moat fills a ring where impact-brecciated rock was eroded away by glaciation.
All the previous aerial images were taken from GOZooM below 5,000 feet above ground.
7. Ground Exploration – 2006
Chuck O’Dale & Eric Kujala (1964-2017)
My ground exploration of impact structures continued in August of 2006 when Eric Kujala and I explored the east area of the Manicouagan Impact Crater by canoe.
At this point I want to strongly recommend AGAINST exploring this body of water by canoe. The weather in this area changes within minutes creating dangerous waves in the annular moat (see below), and being in a canoe that is full of rocks in those conditions is not a good idea!
Driving north to the Manicouagan structure I specifically watched the changing rock faces along the road as we entered the area of the 100 kilometre diameter structure. In the inner fracture zone of the structure, some of the rock faces along the highway changed from solid granite faces to fractured walls.
We had a short wind delay here before we made our dash for the main island of the structure that is just visible in the image over 10 km away. At the time this picture was taken, the wind was subsiding with barely a whitecap to be seen and we started our canoe trip across the moat. We got half way across before the wind increased again! Fortunately by that time we were in the lee of the couple of islands visible in the distance. Paddling against the wind took us most of the day to finally reach our main island camp location.
These photos illustrate the typical breccia outcrops found within the central peak area of the Manicouagan Impact Crater located in Quebec, Canada.
Impact breccias: country geology melted, mixed, crushed and compressed by shock waves at various stages in the cratering process. Even within the brief formation time of an impact crater, it is possible for the multiple generations of breccia to develop and to produce distinctive differences, even though the time between one breccia generation and the next may be measured in seconds or minutes (French 1998).
Impact related pseudotachylite was first recognized at the Vredefort crater in Africa and are common within the Sudbury impact structure.
The colour of the breccia filled rocks around Memory Bay varied from white to copper to dark-mafic.
From location #3 we had a hard uphill slog against the wind to the shock impact melt cliff on the south shore. We eventually made it to the south shore where I walked to the impact melt cliffs shown here at location #4.
Shatter cones at Manicouagan formed over varying shock pressure ranges. A comparison of the shat-ter cones collected along a radial tracsect from 27 to 12 km from the centre of the structure reveal a systematic in-crease in the intensity of shock metamorphism recorded by the quartz and oligoclase indicating an increase in shock pressure from ~5 GPa to ~30 GPa. The most shocked oligoclase sample preserves textures indicative of dynamo-thermal conditions and not just static high pressure (ductile and melt textures). (L. M. Thompson, et al 2016)
The passage of the shock wave through the rock changes the structure of some of the enclosed minerals. IE: change is possible in the feldspar mineral plagioclase. The shock wave can break down the structure of the mineral, changing parts of it into a diapletic glass (glass formed at high-pressure in the solid-state) which is isotropic, or uniform in all directions. This photograph of a thin slice of plagioclase, 0.03 millimetre thick, is seen here in cross-polarised light, with a ‘sensitive tint’ plate. The original plagioclase is coloured yellow and the shock-changed mineral is purple. This sample is from the Manicouagan impact crater. (Courtesy Denis W. Roy & MIAC).
This series of cartoons by Denis W. Roy illustrates the sequence of events that formed the Manicouagan impact crater, Québec, Canada. (Courtesy of MAIC)
1 STOKES LAW: If the particles are falling in the viscous fluid by their own weight due to the Earth’s gravity, then a terminal velocity, also known as the settling velocity, is reached when this frictional force combined with the buoyant force exactly balance the gravitational force. The resulting settling velocity (or terminal velocity) is given by:
Vs = ( 2 (ρp – ρf ) / 9 η ) g R2 where:
- Vs is the particles’ settling velocity (m/s) (vertically downwards if ρp > ρf, upwards if ρp < ρf ),
- R is the radius of the spherical object (in metres),
- g is the Earth’s gravitational acceleration (m/s2),
- ρp is the mass density of the particles (kg/m3),
- ρf is the mass density of the fluid (kg/m3), and
- η is the fluid’s viscosity (in [kg m-1 s-1]).
I mentioned earlier that it is not recommended to do this trip by canoe (as we did). The waves on the annular moat and in Memory Bay can reach dangerous heights very quickly. On our final day in the impact structure we were returning to our starting point in Kauashapishkau Bay in a semi-calm wind. But within 20 minutes the wind had increased from under 10 kts to greater than 30 kts! We had to perform an emergency beaching on an island 1/3 of the way across the annular moat.
We made it onto the beach by surfing the waves! It was fortunate that Eric was an experienced white water canoe operator, as we may have otherwise been dumped. Here, we had just started a fire to dry ourselves off. We will be marooned here for 22 hours waiting for the winds to subside. So, what to do until the wind subsides? Why, explore of course!
We eventually made it off the island at 5AM the next morning. Within 15 minutes of waking up during a wind lull, we had struck camp and were paddling for dear life for the eastern shore of the annular moat! We made it back across the reservoir without incident in under three hours. We had a great tail wind. What an adventure!! It was surreal later that morning eating our hot egg and bacon breakfast in a restaurant and realizing that just hours ago we were marooned without any idea of how long it would be until we could get back to the main land.
Components of the RASC Sesquicentennial Logo:
The aurora borealis is a quintessentially Canadian space-weather phenomenon, one shared with other high latitude cultures. RASC members have contributed to the scientific, historical, and artistic investigation of the northern lights, and have promoted their recreational enjoyment.
The Manicouagan astrobleme (214 ± 1 Ma) represents the major discovery of sites of impact cratering in the Canadian Shield, an effort pioneered by astrophysicists and geophysicists at the Dominion Observatory (ca. 1950-), many of whom were RASC members. This world-impacting research played a crucial role in changing scientific and popular perceptions of crater-forming mechanisms, solar-system history, and planetary geology. The representation of the crater also acknowledges Canadian excellence in meteor dynamics, meteorite petrology, meteorite curation, and the RASC’s long-standing interest in such work.
The stars represent the major Canadian contributions to stellar spectroscopy done at the Dominion Observatory, the Dominion Astrophysical Observatory (also see this), the David Dunlap Observatory,(additionally refer to this) and elsewhere (ca. 1905-), whose major contributors were also RASC members (such as J.S. Plaskett [1865-1941], the first Canadian astrophysicist of international repute). The stars also symbolize the asteroseismology, exoplanet transits and eclipses, and investigations into stellar variability through precise photometry achieved by the Microvariability and Oscillations of STars space telescope(MOST, 2003-).
The globular cluster recognizes the field of Helen Sawyer Hogg‘s (1905-1993) greatest scientific contributions (ca. 1926-ca. 1993), and the Helen Sawyer Hogg Telescope (HSHT) at the University of Toronto Southern Observatory at Cerro Las Campanas, one of Canada’s first ventures (1971-1997) in exploring off-shore astronomical installations, which has born lasting fruit in international cooperative installations exploring the full range of astrophysical phenomena, such as the Canada-France-Hawaii Telescope (CFHT, 1979-), the James Clerk Maxwell Telescope (JCMT, 1986-2015 [period of direct Canadian involvement & funding]), the Gemini Telescopes (North 1999-, South 2000-), the Atacama Large Millimetre Array (ALMA, 2011/2013-), the Square Kilometre Array (SKA, 2020-), and the Thirty Metre Telescope (TMT, ca. 2022-).
The spiral galaxy represents both the work of Canadian observational cosmologists (e.g., Sidney van den Bergh‘s classification of Galaxy morphology, Laura Ferrarese‘s work on the morphology & dynamics of early type galaxies), as well as the efforts of amateur Canadian observers of deep-sky objects (DSOs), and imagers.
The Moon symbolizes an object important for first nations’ calendrics, and the earliest recorded observations by Europeans in Canada (17th century lunar reports, and lunar eclipse reports). The Moon together with the stars symbolizes the practice of navigational astronomy on land and water, which was crucial to the formation of Canada. Finally, the Moon is as popular an object for RASC members to share with the public when doing outreach as it was 150 years ago.
RASC AstroNotes Article (September 2010)
from (AstroNotes October 2010😉 – I included the geology from our exploration of the Manicouagan Impact Crater as examples for “Identifying Impact Craters/Structures”.
~214 Ma – LATE TRIASSIC EXTINCTION
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.
[see – METEORITE]
AMOR, Kenneth, HESSELBO, Stephen P., and PORCELLI 2005, GEOCHEMICAL ANALYSIS OF A LATE TRIASSIC DISTAL IMPACT EJECTA LAYER FROM SW ENGLAND. Donald Department of Earth Sciences, University of Oxford.
Brent Dalrymple, Radiometric Dating Does Work! Reports of the National Center for Science Education
Michael J. Clutson, David E. Brown, Lawrence H Tanner Distal Processes and Effects of Multiple Late Triassic Terrestrial Bolide Impacts: Insights from the Norian Manicouagan Event, Northeastern Quebec, CanadaResearch Gate 2018
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.
Dence, M.R., Bunch T.E. Cohen A.J. NATURAL TERRESTRIAL MASKELYNITE, THE AMERICAN MINERALOGIST 1967
Dence, M. R. 1976 The Manicouagan impact structure. NASA Spec. Pub.
French, Bevan M. 1998. Traces of Catastrophe, A handbook of Shock-Metamorphic effects, Lunar and Planetary Institute.
R. A. F. Grieve et al , Manicouagan Impact Melt, Quebec, 1, Stratigraphy, petrology, and chemistry 1978
Haskin, L et al 1998, The case for an Imbrium origin of the Apollo thorium-rich impact-melt breccias. Meteoritics & Planetary Science, vol. 33, no. 5, pp. 959-975.
Murtaugh, J.G. 1972, Shock metamorphism in the Manicouagan cryptoexplosion structure, Quebec. Proc. 24th Int. Geol. Congr.
O’Dale, C.P. 2006; Manicouagan Impact Structure
Onoue T. et al; Deep-sea record of impact apparently unrelated to mass extinction in the Late Triassic. National Academy of Sciences, 2012
Onoue T. et al; Bolide impact triggered the Late Triassic extinction event in equatorial Panthalassa. Scientific Reports, 2016
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
Orphal, D & Schultz, P, An alternative model for the Manicouagan impact structure. Proc Lunar Planet Sci Conf 1978.
Simonds, C.H. et al 1976, Thermal model for impact breccia lithification: Manicouagan and the moon. Proc. Lunar Sci. Conf. 7th (1976) p. 2509-2528.
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.
L. M. Thompson, J. Brown and J. G. Spray, SHATTER CONES, SHOCK ATTENUATION AND FELDSPARS: MANICOUAGAN IMPACT STRUCTURE, CANDA. 79th Annual Meeting of the Meteoritical Society (2016)
- PHOTOGRAPHIC IMAGES: Eric Kujala and Charles O’Dale.