The Emeishan Traps constitute a
flood basalt
A flood basalt (or plateau basalt) is the result of a giant volcanic eruption or series of eruptions that covers large stretches of land or the ocean floor with basalt lava. Many flood basalts have been attributed to the onset of a hotspot (geolo ...
volcanic province, or
large igneous province
A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive ( sills, dikes) and extrusive (lava flows, tephra deposits), arising when magma travels through the crust towards the surface. The format ...
, in south-western China, centred in
Sichuan
Sichuan is a province in Southwestern China, occupying the Sichuan Basin and Tibetan Plateau—between the Jinsha River to the west, the Daba Mountains to the north, and the Yunnan–Guizhou Plateau to the south. Its capital city is Cheng ...
province. It is sometimes referred to as the Permian Emeishan Large Igneous Province or Emeishan Flood Basalts. Like other
volcanic
A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
On Earth, volcanoes are most often fo ...
provinces or "
traps", the Emeishan Traps are multiple layers of
igneous rock
Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava.
The magma can be derived from partial ...
laid down by large
mantle plume
A mantle plume is a proposed mechanism of convection within the Earth's mantle, hypothesized to explain anomalous volcanism. Because the plume head partially melts on reaching shallow depths, a plume is often invoked as the cause of volcanic ho ...
volcanic eruptions. The Emeishan Traps eruptions were serious enough to have global
ecological
Ecology () is the natural science of the relationships among living organisms and their environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere levels. Ecology overlaps with the closely re ...
and
paleontological
Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...
impact.
It is named for
Emeishan, a mountain in Sichuan.
Etymology
The term "
trap" has been used in
geology
Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...
since 1785–1795 for such
rock formation
A rock formation is an isolated, scenic, or spectacular surface rock (geology), rock outcrop. Rock formations are usually the result of weathering and erosion sculpting the existing rock. The term ''rock Geological formation, formation ...
s. It is derived from the Swedish word for stairs ("trappa") and refers to the step-like hills forming the landscape of the region.
Formation and development
The eruptions that produced the Emeishan Traps began 265 million years ago (Ma) or earlier.
The main eruptive period is between 262 and 261 Ma, and the volcanism activities end 259 Ma.
In volume, the Emeishan Traps are dwarfed by the massive
Siberian Traps
The Siberian Traps () are a large region of volcanic rock, known as a large igneous province, in Siberia, Russia. The massive eruptive event that formed the trap rock, traps is one of the largest known Volcano, volcanic events in the last years ...
, which occurred, in terms of the
geological time scale
The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronolo ...
, not long after, at approximately 252 Ma. The Emeishan
basalt
Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...
s covers an area of more than 250,000 km
2 with thicknesses ranging from several hundred meters up to 5.5 km (the average flood basalt thickness throughout the entire region is estimated to be around 700 m), but the Emeishan traps may have initially covered an area as much as 500,000 km
2. Thus the entire volume of the Emeishan basalts is estimated to be 300,000 km
3. Evidence suggests that the initial volcanism of the central Emeishan Traps occurred in a deep submarine environment without any significant prevolcanic uplift.
The Emeishan Traps are associated with the end-
Capitanian mass extinction event, the extinction of
animal
Animals are multicellular, eukaryotic organisms in the Biology, biological Kingdom (biology), kingdom Animalia (). With few exceptions, animals heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, ...
and
plant
Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...
life that occurred at the end of the
Capitanian
In the geologic timescale, the Capitanian is an age or stage of the Permian. It is also the uppermost or latest of three subdivisions of the Guadalupian Epoch or Series. The Capitanian lasted between and million years ago. It was preceded by t ...
stage of the Guadalupian
epoch
In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured.
The moment of epoch is usually decided b ...
of the
Permian
The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...
period. Limestone within the traps show the extinction to occur immediately below the first eruptive unit, with the mass extinction marked at the onset of explosive Emeishan volcanism.
The formation of volcaniclastics suggest violent
phreatomagmatic-style eruptions.
The synchrony between the Emeishan Traps and the
end-Guadalupian extinction has been taken to support the argument of
Vincent Courtillot and others that volcanism is the main driver of mass extinctions.
After their emplacement, the Emeishan Traps were eroded and their minerals became encased in coals that formed after their emplacement.
See also
*
Deccan Traps
The Deccan Traps are a large igneous province of west-central India (17–24°N, 73–74°E). They are one of the largest volcanic features on Earth, taking the form of a large shield volcano. They consist of many layers of solidified flood ...
*
Viluy Traps
*
List of flood basalt provinces
*
Siberian Traps
The Siberian Traps () are a large region of volcanic rock, known as a large igneous province, in Siberia, Russia. The massive eruptive event that formed the trap rock, traps is one of the largest known Volcano, volcanic events in the last years ...
References
;Citations:
;Bibliography:
*
*
*
* Koeberl, Christian, and Francisca C. Martinez-Ruiz, eds. (2003) ''Impact Markers in the Stratigraphic Record.'' New York, Springer-Verlag.
* Yuen, David A., Shinegoru Maruyama, Shun-Ichiro Karato, and Brian F. Windley, eds. (2007) ''Superplumes: Beyond Plate Tectonics.'' New York, Springer-Verlag.
External links
Age of the Emeishan Flood Magmatism and Relations to Permian-Triassic Boundary Events.- "Re-evaluating plume-induced uplift in the Emeishan large igneous province"
Science- "Volcanism, Mass Extinction, and Carbon Isotope Fluctuations in the Middle Permian of China"
{{Large igneous provinces
Large igneous provinces
Permian volcanism
Geography of Sichuan
Volcanism of China