Global mass wasting during the Middle Ordovician: Meteoritic trigger or plate-tectonic environment?
Research highlights
►The research highlights of our paper are the presentation of alternative explanations for the global mass wasting during the Middle Ordovician, which has recently been related to high meteorite influx. We argue that nearly all of these deposits can be related to terrestrial processes (i.e. plate tectonics, sea level changes) and give a short summary of each location with its alternative explanation.
Introduction
The Earth's geological record shows mass wasting deposits from the Precambrian to Recent (e.g., Bugge et al., 1987, Hine et al., 1992, Hampton et al., 1996, Spence and Tucker, 1997, Keller et al., 1998, Hoffman and Hartz, 1999, Keller, 1999, Woodcock and Morris, 1999, Weaver et al., 2000, Cooper et al., 2001, Piper et al., 2003, Clift et al., 2004, Maslin et al., 2004, Locat and Lee, 2005, Wendorff, 2005, Ryu et al., 2005, Moscardelli et al., 2006, Valverde-Vaquero et al., 2006, Gee et al., 2007, Ratzov et al., 2007, Callot et al., 2008, Lee, 2009, Strozyk et al., 2009, Hornbach et al., 2010).
The present study focuses on Middle Ordovician mass wasting deposits, comprising mainly sedimentary megabreccias with maximum clast sizes from 1 m to > 1 km, which were deposited along the margins of different palaeo-continents, e.g., Avalonia, and on volcanic arcs (Fig. 1). This mass wasting at continental margins on a global scale has recently been related to earthquake-driven slope failure following meteorite impacts (Parnell, 2009). This hypothesis is based on the observation that these megabreccias overlap in time with enhanced occurrence of extraterrestrial chromite and a shift to lower 187Os/188Os values in an essentially continuous sequence of Middle Ordovician shallow marine limestones of southern Sweden and several thousand kilometres away in central China (Schmitz et al., 2001, Schmitz et al., 2003, Schmitz et al., 2008). They were deposited a few million years after the disruption of the L-chondrite parent body in the asteroid belt at about 470 ± 6 Ma ago (Korochantseva et al., 2007) (Fig. 2). Using semiquantitative calculations, Parnell (2009) suggested that up to 500 impactors of 100 m in diameter, including 250 impactors if only landward impacts are considered, fell within about 30 km of the 20,000 km long Iapetus coastline. The disruption of a parent body in the asteroid belt will lead to enhanced meteorite influx on Earth in less than one or a few million years (e.g., Schmitz et al., 2001) and may affect the Earth's surface with a number of impact craters. Table 1 lists the known impact structures of Ordovician age but interestingly only three craters within the age range of the megabreccias (468–461 Ma) have been found so far. Furthermore, shatter cones, microscopic planar deformation features (PDFs) in quartz, high-pressure mineral phases and high-temperature glasses and melts (or their relics) related to impact events (e.g., Dypvik and Jansa, 2003, French and Koeberl, 2010) have not yet been found in 468–461 Ma-old strata, although that may simply be because these features have been overlooked or may have been destroyed by terrestrial processes (e.g., erosion, subduction) since their formation (French and Koeberl, 2010). Two exceptions are PDFs in quartz grains from Darriwilian breccias of the Osmussaar area in northwestern Estonia and from a polymict breccia of the Granby structure in Sweden. The former are likely recycled ejecta material from the nearby early Cambrian Neugrund crater (Suuroja et al., 2003, Ainsaar et al., 2007), whereas the latter may be real impact-related features of Middle Ordovician age (Alwmark, 2009).
In our opinion, earthquake-driven slope failure producing the Middle Ordovician mass wasting was not necessarily caused by bombardment of the Earth's surface with large meteorites over a period of almost 10 Ma. The most striking and important feature, which led to our alternative hypothesis, is the distribution of the mass wasting sites along and close to active continental margins, arc terranes, and rift basins in Middle Ordovician palaeotectonic reconstructions (Fig. 1). Note that in the Quaternary, for instance, all active continental margins (e.g., Gee et al., 2007, Ratzov et al., 2007, Strozyk et al., 2009, Hornbach et al., 2010, and references therein) and passive margins (e.g., Bugge et al., 1987, Piper et al., 2003, Lee, 2009, and references therein) have large mass wasting deposits. Thus, finding them in the Middle Ordovician sedimentary record is not surprising.
In this paper, we present an alternative explanation for the global Middle Ordovician mass wasting without the need of extraterrestrial support. We propose that destabilisation of continental margins causing this global mass wasting was simply due to earthquakes and instability of slopes, related to plate-tectonic processes. Global sea level changes may also have triggered destabilisation of carbonate platforms and continental margin sediments. Nonetheless, we want to emphasise that we do not neglect the enhanced influx of extraterrestrial material on the Earth during the Ordovician. This influx has probably been responsible for local mass wasting (e.g., Hummeln structure: Lindström et al., 1999; Kärdla structure: Lindström, 2003) rather than global.
Section snippets
Mass wasting
Mass wasting is a general term describing down slope movement of sediment and rock. Common mass wasting deposits are debris flows, slides and slumps (e.g., Bugge et al., 1987, Einsele, 1993, Weaver et al., 2000, Locat and Lee, 2005, Lee, 2009). The formation of mass wasting deposits depends on the configuration of the terrain and relies on soil and rock mechanics parameters and failure criteria (Locat and Lee, 2005). Submarine slides, for instance, are most common in fjords, active river deltas
Earth's extraterrestrial influx
The Earth has suffered meteorite bombardment ever since its formation with fluctuating intensity but only under certain circumstances has it been recorded (e.g., Peucker-Ehrenbrink and Schmitz, 2001, Schmitz et al., 2001, Dypvik and Jansa, 2003, Lindström, 2003, Spray, 2009, French and Koeberl, 2010). About 40,000 tonnes of extraterrestrial material fall to the Earth each year (Brownlee, 2001). For example, about 14,000 meteorite fragments have been collected from a ~ 2500 km2 large area of the
Ordovician mass wasting localities
Parnell (2009) described 12 megabreccia localities from various sites along the margins of the Iapetus Ocean and other parts of the Middle Ordovician globe (Fig. 1, Fig. 2). In addition, debris flow deposits from NW Argentina and Western Yunnan were mentioned. Some of these breccias and debris flows belong to carbonate platforms, which were deposited during relative sea level lowstand (Fig. 2). In general, the megabreccias contain clasts up to kilometre size embedded in a fine-grained
Plate tectonics
Throughout the Ordovician period, magmatism, terrane accretion and back-arc rifting, related to subduction of oceanic lithosphere, chiefly of the Iapetus Ocean, occurred along the margins of Avalonia, Ganderia, Laurentia and Gondwana (e.g., Bird and Dewey, 1970, Dewey and Mange, 1999, Friedrich et al., 1999, Soper et al., 1999, Cocks, 2001, Stampfli and Borel, 2004, Thomas and Astini, 2003, Clift et al., 2004, Valverde-Vaquero et al., 2006, Ryan, 2008, von Raumer and Stampfli, 2008, Fergusson,
Summary of alternative explanations for the mass wasting sites
As outlined above, most of the mass wasting during the Middle Ordovician can simply be explained by seismic-induced slope instability related to plate-tectonic processes. Global sea level changes (in particular sea level falls) may have also had a significant influence. Possible explanations for the formation of the mass wasting on different palaeo-continents during the Middle Ordovician are given below, whereby the numbers in brackets refer to the mass wasting localities discussed, as shown in
Conclusions
Although meteorite impacts caused modifications of the Earth's surface ever since its formation, in the case of the mass wasting during the Middle Ordovician, they may have had only regional impact rather than global. Furthermore, preserved meteorite fragments or relict minerals (e.g., chromite: Schmitz et al., 2001, Schmitz et al., 2003, Schmitz et al., 2008) in Middle Ordovician shallow marine limestone of southern Sweden and in central China do not necessarily indicate that an impact event
Acknowledgments
We gratefully thank Jürgen F. von Raumer for his stimulating discussions and support during the preparation of the manuscript. Thanks go also to David J. W. Piper for his comments on an earlier version of the manuscript and to Robert Scott for polishing the English text. Reviews by two anonymous reviewers and editorial handling by Damian Nance are gratefully acknowledged. This paper is a contribution to the IGCP projects 497 and 503.
References (81)
- et al.
Darriwilian high energy sedimentary facies in Baltoscandia — possible responses to meteorite shower?
Shocked quartz grains in the polymict breccia of the Granby structure, Sweden―verification of an impact
Meteoritics & Planetary Science
(2009)- et al.
The mid-Ordovician Osmussaar breccia in Estonia linked to the disruption of the L-chondrite parent body in the asteroid belt
Geological Society of America Bulletin
(2010) - et al.
Lithosphere plate–continental margin tectonics and the evolution of the Appalachian Orogen
Geological Society of America Bulletin
(1970) The origin and properties of dust impacting the Earth
- et al.
A giant three-stage submarine slide off Norway
Geo-Marine Letters
(1987) - et al.
Giant submarine collapse of a carbonate platform at the Turonian–Coniacian transition: the Ayabacas Formation, southern Peru
Basin Research
(2008) - et al.
The meteorite collection sites of Antartica
Meteoritics
(1992) - et al.
Rapid tectonic exhumation, detachment faulting and orogenic collapse in the Caledonides of western Ireland
Tectonophysics
(2004) Ordovician and Silurian global geography
Journal of the Geological Society of London
(2001)
Baltica from the late Precambrian to mid-Palaeozoic times: the gain and loss of terrane's identity
Earth Science Reviews
Basin evolution in western Newfoundland: new insights from hydrocarbon exploration
American Association of Petroleum Geologists Bulletin
Petrology of Ordovician and Silurian sediments in the western Irish Caledonides: tracers of short-lived Ordovician continent–arc collision orogeny and the evolution of the Laurentian Appalachian–Caledonian margin
Sedimentary signatures and processes during marine bolide impacts: a review
Sedimentary Geology
Marine depositional events controlled by sediment supply and sea-level changes
Geologische Rundschau
Tectonic evolution of the Ordovician Macquarie Arc, central New South Wales: arguments for subduction polarity and anticlockwise rotation
Australian Journal of Earth Sciences
The convincing identification of terrestrial meteorite impact structures: what works, what doesn't, and why
Earth-Science Reviews
Short-lived continental magmatic arc at Connemara, western Irish Caledonides: implications for the age of the Grampian orogeny
Geology
The Brunei slide: a giant submarine landslide on the North West Borneo Margin revealed by 3D seismic data
Marine Geology
A Geologic Time Scale 2004
Precise chitinozoan dating of Ordovician impact events in Baltoscandia
Journal of Micropaleontology
The Hølonda Porphyrites, Norwegian Caledonides: geochemistry and tectonic setting of Early–Mid-Ordovician shoshonitic volcanism
Journal of the Geological Society of London
Submarine landslides
Reviews of Geophysics
A chronology of Paleozoic sea-level changes
Science
Megabreccia shedding from modern low-relief carbonate platforms, Nicaraguan Rise
Geological Society of America Bulletin
Carbonate debris flows, Cow Head Group, Western Newfoundland
Journal of Sedimentary Petrology
Large, coherent, submarine landslide associated with Pan-African foreland flexure
Geology
Estimating the age of near-shore carbonate slides using coral reefs and erosional markers: a case study from Curacao, Netherlands Antilles
The Sedimentary Record
Argentine Precordillera: sedimentary and plate tectonic history of a Laurentian crustal fragment in South America
Geological Society of America Special Paper
Sedimentology of Middle Ordovician carbonates in the Argentine Precordillera: evidence of regional relative sea-level changes
Geologische Rundschau
The stratigraphical record of the Argentine Precordillera and its plate-tectonic background
The Ordovician St. George Unconformity, northern Appalachians: the relationship of plate convergence at the St. Lawrence Promontory to the Sauk/Tippecanoe sequence boundary
Geological Society of America Bulletin
Submarine silicic volcanism and associated sedimentary and tectonic processes, Ramsey Island, SW Wales
Journal of the Geological Society of London
L-chondrite asteroid breakup tied to Ordovician meteorite shower by multiple isochron 40Ar–39Ar dating
Meteoritics & Planetary Science
The Great Sumatra–Andaman Earthquake of 26 December 2004
Science
Timing of occurrence of large submarine landslides on the Atlantic Ocean margin
Marine Geology
An array of offshore impact craters on Mid-Ordovician Baltica
The Lower Palaeozoic of the probable impact crater of Hummeln, Sweden
GFF
Subaqueous debris flows
The source of the Cow Head Breccias of Western Newfoundland: new evidence
Journal of Geology
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