End-Permian catastrophe by a bolide impact: Evidence of a
gigantic release of sulfur from the mantle
Kunio Kaiho* Institute of Geology and Paleontology, Tohoku University, Sendai 980-8578, Japan
Yoshimichi Kajiwara 
 Institute of Geoscience, University of Tsukuba, Ibaraki 305, Japan
Takanori Nakano
Yasunori Miura Department of Earth Sciences, Faculty of Science, Yamaguchi University, Yamaguchi 753-8512, Japan
Hodaka Kawahata Marine Geology Department, Geological Survey of Japan, Ibaraki 305-8567, Japan
Kazue Tazaki
 Department of Earth Sciences, Kanazawa University, Kanazawa 920-1192, Japan
Masato Ueshima 
Zhongqiang Chen  School of Ecology and Environment, Deakin University, Rusden Campus, 662 Blackburn Road, Clayton,

Victoria 3168, Australia
Guang R. Shi
ABSTRACT
Our studies in southern China have revealed a remarkable sulfur and strontium isotope
excursion at the end of the Permian, along with a coincident concentration of impactmetamorphosed grains and kaolinite and a significant decrease in manganese, phosphorous, calcium, and microfossils (foraminifera). These data suggest that an asteroid or a
comet hit the ocean at the end of Permian time and caused a rapid and massive release
of sulfur from the mantle to the ocean-atmosphere system, leading to significant oxygen
consumption, acid rain, and the most severe biotic crisis in the history of life on Earth.
Keywords: mass extinctions, Permian, S-34/S-32, Sr-87/Sr-86, impact metamorphism, elements, clay minerals.
INTRODUCTION
Although it is widely held that an extraterrestrial impact caused the extensive mortality
at the Cretaceous-Tertiary (K-T) boundary 65
m.y. ago (Alvarez, 1986; Kaiho and Lamolda,
1999; Sheehan et al., 2000), we do not yet
know the cause of Earth’s most severe biotic
crisis, which occurred at the end of Permian
time, some 251 m.y. ago (Bowring et al.,
1998). Understanding the cause of this event
is important because it represents the largest
mass extinction and led to the subsequent
origination of the Holocene biota on Earth
(Erwin, 1993).
Until recently, latest Permian biological and
environmental changes were thought to be
more gradual than those recorded at the K-T
boundary and the associated extraterrestrial
impact event (see Erwin, 1993, for a review).
Most earth scientists have called on other
causes, including gradual sea-level fall, climate change, oceanic anoxia, and volcanism,
to explain the end-Permian event (Erwin,
1994). Recent work has provided evidence indicating that an abrupt end-Permian extinction
occurred among organisms in both marine and
terrestrial environments (Erwin, 1993; Retallack, 1995; Eshet et al., 1995; Bowring et al.,
1998; Rampino and Adler, 1998; Jin et al.,
2000). Becker et al. (2001) reported that some
end-Permian sediments contain fullerenes
with trapped noble gases that are indicative of
an extraterrestrial source.
*E-mail: [email protected].
Our study of the end-Permian biotic crisis
involved geochemical and paleontological
analyses of well-preserved samples from the
Meishan stratigraphic sections (A and D) located in southern China, which contain sediments representing latest Permian shallow marine environments. Lithology of the two study
sections is very similar (Fig. 1). The PermianTriassic (P-T) boundary was identified in the
Meishan sections on the basis of biostratigraphy and determined to be in the middle of
marl bed 27 (Yin, et al., 1996); the eventstratigraphic P-T boundary (EPTB) was
placed at the base of bed 25 (Wang, 1994).
We focused our efforts on the 60-cm-thick interval spanning the EPTB and obtained unweathered samples1 by taking large blocks using a large hammer. Very thin laminae (0.1 to
0.5 mm) near the EPTB were sliced by a knife
in our laboratory.
ABRUPT MASS EXTINCTIONS
Compilations of paleontological records
from the Meishan sections show that the last
appearances of most marine genera are concentrated in the top 20 cm of Permian limestone in bed 24e (Fig. 2). Rapid decreases in
foraminifera (,1/10; Appendix 1; see footnote 1) and possible proxies for biomass including phosphorous (;1/4) and calcium
1GSA Data Repository item 2001092, Appendix
1, Methods and data, is available on request from
Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301-9140, [email protected], or at
www.geosociety.org/pubs/ft2001.htm.
(;1/4), and a coincidental tenfold to twentyfold increase in Ni (a possible proxy for an
extraterrestrial impact) are found 2 cm below
the top of bed 24e (Fig. 1). These data suggest
that a mass extinction and a rapid decrease in
biomass coincided with the increase in Ni.
Similar changes have been recorded within the
impact layer marking the K-T boundary (Kaiho et al., 1999).
OCEAN IMPACT
Fullerenes found in end-Permian sediments
contain trapped helium and argon with isotope
ratios similar to the planetary component of
carbonaceous chondrites (Becker et al., 2001).
This implies that an impact event (asteroidal
or cometary) accompanied the extinction. Our
data show that Ni is concentrated in the top 2
cm of bed 24e and the overlying basal part
(25–1; 0.1 mm thick) of bed 25. The Ni-rich
layers have many magnetic fragments that
contain grains (2–50 mm in diameter) of FeSi-Ni (Table 1) in a matrix of FeS or Si-KCa-Al–bearing materials. Grains of similar
composition have been found at some impact
craters and at the K-T boundary (Miura et al.,
1999). The impact of a meteorite having a diameter .1 km would have caused an increase
in temperature of up to 10 000 8C near the
impact point and from 500 to 3000 8C in much
of the surrounding rock (Grieve et al., 1977;
French, 1998). Projectile meteoroids accompanying such an impact would have completely evaporated; Fe and Ni in the meteoroids
would have separated and mixed with Si or Al
in the oceanic crust and mantle, resulting in
the formation of Fe-Si-Ni grains (Miura et al.,
1999, 2000). Grains composed of Fe-Si-Ni
system material can remain after vapor impact
reaction. Spherules from volcanic rocks are
characterized by volatile elements and are Ni
poor because of the mixing of crustal rocks
and magmatic liquids at temperatures #1200
8C (Miura et al., 1999). This latter temperature
is too low to produce grains of Fe-Si-Ni composition, because their boiling temperatures
are high (Fe: 2890 8C, Ni: 2863 8C, Si: 2227
q 2001 Geological Society of America. For permission to copy, contact Copyright Clearance Center at www.copyright.com or (978) 750-8400.
Geology; September 2001; v. 29; no. 9; p. 815–818; 2 figures; 1 table; Data Repository item 2001092.
815
Figure 1. Variations in lithology and geochemistry of sediments recorded in Upper Permian and Lower Triassic layers
in Meishan sections A and D, southern China. Bed numbers are after Yin et al. (1996). CDT is Canyon Diablo Troilite.
Base of Fe-rich black layer is defined as 0 cm; positive and negative numbers correspond to thickness above and below
latter horizon.
8C). Therefore, the presence of grains of FeSi-Ni also represents evidence for an impact
event. The lack of shocked quartz in endPermian samples and the apparent absence of
a large continental impact crater suggest that
a bolide hit the ocean and oceanic crust at the
end of the Permian.
Figure 2. Percentages of
last occurrences of Permian marine genera per
meter in each bed in Upper Permian and Lower
Triassic Meishan sections, southern China; recorded genera are fusulina, other foraminifera,
brachiopoda,
bivalvia,
ammonoidea, corals, bryozoa, gastropoda, and
fish. Data compiled from
Zhao et al. (1981), Sheng
et al. (1984), Yang et al.
(1987), Yin et al. (1996),
and Chen et al. (1999).
816
RELEASE OF SULFUR
The sulfur isotope ratio (d34S) of sulfate,
relative to the international standard Canyon
Diablo Troilite (CDT), rapidly decreases from
;20‰ in the uppermost Permian limestone
bed 24e to ;5‰ in the lower part of the Niconcentrated layer (24e–2), then increases to
;10‰ in marl bed 27 (Fig. 1). The strontium
isotope ratio of leachate obtained by acetic
acid (87Sr/86SrHOAC-leachate; 0.7072–0.7079;
Fig. 1), is similar to that of contemporaneous
seawater (0.7074–0.7075; Burke et al., 1982;
Popp et al., 1986), except for a sample from
dark gray shale bed 26, suggesting no evidence of diagenetic effects within these
samples.
It is impossible for us to compare our results with other sulfate sulfur isotope data because no data on sulfate sulfur isotopes have
previously been reported near the P-T boundary (6105 yr). Our data and the generalized
trend of d34S (sulfate) reported by Claypool et
al. (1980) show minimum values at the end of
the Permian. However, the values are different, and a distinct positive shift of d34S just
below the EPTB offers new insights into this
event. The d34S values recorded stratigraphically above the EPTB are mostly the same as
those of Claypool et al. (1980). On the basis
of these facts, our data are thought to monitor
global changes of d34S sulfate, but the possibility of local values cannot be excluded, because of a lack of contemporaneous data.
The negative shift of the sulfur isotope ratio
implies an enormous release and injection of
isotopically light sulfur to the ocean-atmo-
GEOLOGY, September 2001
TABLE 1. ELEMENT COMPOSITIONS OF REPRESENTATIVE GRAINS FROM END-PERMIAN MASS
EXTINCTION LAYERS IN MEISHAN, SOUTHERN CHINA
Bed no.,
section
25-1,
25-1,
25-1,
24-3,
24-3,
D
D
A
A
A
Grain size
(mm)
2
2
2
10 3 20
25 3 50
Atomic element (wt% of grains)
Fe
Si
Ni
Al
K
Ca
Cr
Mn
Cu
Co
73.2
90.8
89.6
85.2
67.7
20.2
6.6
7.8
2.0
1.9
1.5
2.0
2.2
9.2
8.6
4.2
0
0
2.8
2.4
1.0
0
0.4
0.1
0
0
0.6
0
0
0
0
0
0
0
16.1
0
0
0
0
1.9
0
0
0
0.8
0.3
0
0
0
0
1.1
sphere system. Possible sources of the light
sulfur include mantle rocks, volcanic acid,
crustal rocks, sediments, asteroids, and comets, on the basis of their values of sulfur isotope ratio being approximately 0‰ (Holser et
al., 1988). Significant isotope fractionation
does not occur by oxidation of sulfide. The
thermal decomposition of pyrite and troilite
(or pyrrhotite) releases elemental sulfur, resulting in a 34S/32S ratio that is 12‰ to 13‰
smaller than that of the undissociated material;
this isotopic effect has little, if any, temperature dependence (McEwing et al., 1980; Kajiwara et al., 1981). Therefore, lighter sulfur
(d34S ; 210‰) is released to the atmosphere
when partial evaporation of elemental sulfur
occurs. A bolide impact on Earth would have
caused an abrupt release of reduced and oxidized sulfur in vaporized projectiles and ejecta
because of the low boiling temperature of sulfur (S: 445 8C; SO242: ;317 8C, in 1 atm)
relative to temperature at an impact area (500–
10 000 8C) and mantle (;1200 8C). The reduced sulfur (present mainly as pyrite or pyrrhotite in terrestrial rocks and meteorites)
would have been vaporized and oxidized according to the chemical reactions below, and
the oxidation would have led to deposition of
isotopically light sulfate sulfur, consumption
of oxygen, and precipitation of acid rain:
FeS2
(2S 22 )
1 7/2O2 1 H2O
→ Fe 21 1 2SO422 1 2H1 ,
(1)
FeS(S 22 ) 1 O2 1 2H2O
→ Fe 21 1 SO422 1 4H1 .
(2)
The sulfur released would have condensed in
the neritic Permian sea because of the presence of sulfur from river sources, resulting in
low values of ;5‰. After complete mixing
of seawater in the global ocean, d34Ssulfate
probably reached ;10‰, as observed in bed
27. The 10‰ decrease in the sulfate sulfur
isotopic ratio in the ocean is attributed to the
rapid injection of light sulfur (;210‰ to 0‰
in the case of partial evaporation or complete
evaporation) and mixing with oceanic sulfur
(;20‰). Therefore, the decrease implies release of vaporized sulfur approximately equivalent to half of the possible total of sulfur in
the oceans (2 3 1019 to 4 3 1019 mol). How-
GEOLOGY, September 2001
ever, the size of the crater would be similar
whether evaporation was partial or complete.
SCALE OF THE IMPACT
Because most of the vaporized reduced sulfur would have been oxidized in the atmosphere, we can estimate the radius of the impact crater:
VrS 3 1/32 5 4 3 1019 [mol],
V ù 4/3pr 3 3 1/3,
(3)
where V (cm3) is the volume of excavated material from the crater, r is the density of the
ejecta (;4), S is sulfur content in the upper
mantle (;1000 ppm in mid-oceanic-ridge basalt to ;8000 ppm in original Loihi magma,
calculated from sulfur content and d34S in
Loihi alkali basalt; Sakai et al., 1982, 1984;
Sakai and Matsuhisa, 1996), and r (cm) is the
radius of the crater, which in this case is ;300
to ;600 km. In turn, the estimated diameter
of the crater (600 to 1200 km) corresponds to
the impact of an asteroid 30 to 60 km in diameter or a 15- to 30-km-diameter comet, on
the basis of calculations using a normal velocity and density (asteroid: 20 km/s, 4; comet: 60 km/s, 1). The ocean impact implies that
98% to 99% of available sulfur was supplied
from the mantle.
The impact may have induced large-scale
volcanism such as the coincidental Siberian
flood basalt event (251.2 6 0.3 Ma; diameter
;2000 km; Renne et al., 1995; Bowring et al.,
1998), which released light sulfur to the atmosphere and ocean. Therefore, the estimated
scale of the impact represents a maximum value. Becker et al. (2001) estimated that the size
of the end-Permian bolide was 9 6 3 km, on
the basis of the measured 3He content for the
end-Permian and Murchison fullerenes. In this
case, most of the light sulfur (96% to 99%)
must have been supplied from impact-induced
volcanism.
Sr ISOTOPIC EVIDENCE FOR SUPPLY
OF MANTLE MATERIALS
We also calculated the strontium isotope ratio of residue by HCl at the time of deposition
(87Sr/86SrHCl-residue initial) using (1) the date of
deposition and (2) the amount of Rb and Sr
and 87Sr/86Sr in the residue. The calculated
isotopic values were derived from clastic sed-
iments that came from the sedimentary basin
extant at that time. The values rapidly decrease from 0.715 to 0.708 in the Ni-concentrated layer and increase to 0.733 in the basal
part of marl bed 27 (Fig. 1). The high values
($0.715) imply a continental crust origin
(87Sr/86Sr 5 0.712–0.726; Bowen, 1988),
whereas the low values (0.708) indicate a
mantle origin (87Sr/86Sr 5 0.704; Bowen,
1988). Therefore, the negative excursion implies a change in source of Sr from continental
crust to mantle and then back to continental
crust. However, there is no negative shift of
87Sr/86Sr
HOAC-leachate in the Ni-concentrated
layer.
Possible sources of isotopically light Sr for
marine sediments include volcanic gas, Sr dissolved from the seafloor hydrothermal system,
and ejecta from the mantle. Volcanic gas can
be ignored quantitatively. An increase in dissolved Sr from the seafloor hydrothermal system leads to a decrease in the 87Sr/86Sr of seawater (87Sr/86SrHOAC-leachate). An increase in
ejecta from the mantle causes a decrease in
87Sr/86Sr of clastics (87Sr/86Sr
HCl-residue initial)
and no decrease in 87Sr/86Sr of seawater, because most of the Sr in ejecta do not dissolve
in water. Therefore, a negative shift of 87Sr/
86Sr
HCl-residue initial and the absence of a negative shift of 87Sr/86SrHOAC-leachate indicate that
the source of light Sr was ejecta from the mantle. Rapid supply of mantle material agrees
with the other evidence of an extraterrestrial
impact and the decrease in sulfate sulfur isotope ratios, which leads to our conclusion that
a rapid release of an enormous volume of sulfur from the mantle to the ocean-atmosphere
system occurred as a result of the impact.
OXYGEN CONSUMPTION
Chemical reactions 1 and 2 induced consumption of oxygen, leading to a decrease in
atmospheric oxygen and dissolved oxygen in
ocean water. Chemical formula 2 works when
most of the sulfur is supplied from the mantle.
The percentage of reduced sulfur to total sulfur in the vaporized ejecta at the time of impact is thought to be ;80%, an amount similar to that of Holocene mid-oceanic-ridge
basalt (Sakai et al., 1984). The release of reduced sulfur (1.6 3 1019 to 3.2 3 1019 mol)
at the end-Permian event led to consumption
of 20% to 40% (1.6 3 1019 to 3.2 3 1019
mol) of the available oxygen, on the basis of
formula 2, and assuming that atmospheric (8
3 1019 mol) and oceanic dissolved-oxygen
(;1018 mol) were the same as today’s and that
$90% of the reduced sulfur released was oxygenated. The Mn values recorded probably
correlate with the dissolved-oxygen conditions
of oceanic bottom waters, because Mn accumulates in oxic conditions and is not precip-
817
itated in anoxic bottom-water conditions (Berner, 1980). A distinct decrease in Mn as
recorded in the black layer, and the low values
are found in beds 25 and 26 (Fig. 1), supporting our conclusion that significant oxygen
consumption occurred at the end of the Permian. However, we predict no significant decrease (0.004%) in atmospheric oxygen at the
K-T boundary, on the basis of our calculation
using the amount of sulfur released by that
impact.
ACID RAIN
Chemical reactions 1 and 2 also indicate
that an increase of H1 occurred during the
end-Permian event, in turn leading to acid rain
(H2SO4). Our calculations indicate that the release of sulfur by the end-Permian impact produced 4 3 1019 mol of H2SO4. The impact
also produced NO through reaction between
the atmosphere and the bolide, resulting in the
formation of 1 3 1017 to 1 3 1018 mol HNO3,
on the basis of the equation of Prinn and Fegley (1987). The latter acids may have produced acidified oceanic water with an average
pH of 1.5 to 2.5. However the acids must have
been buffered quickly by released mantle and
crust materials and by rocks on land and in
the ocean. A positive rapid anomaly of the
kaolinite/illite ratio is present in the top 0.5
mm of the Ni-concentrated layer and the overlying black layer (Fig. 1), supporting precipitation of strong acid rain and fast buffering,
because kaolinite is much more stable in acidic conditions than is illite. Acid rain led to an
increase in 87Sr/86Sr of seawater by 0.0002 at
the K-T boundary (Macdougall, 1988). This
suggests that the end-Permian acid rain may
have led to an increase in 87Sr/86Sr of seawater. However, there is no record of 87Sr/86Sr
at the EPTB, because of lack of carbonate.
CONCLUSIONS
All changes recorded in the 2-cm-thick Nirich layer discussed above would have occurred abruptly, because it has a high concentration of impact-metamorphosed grains. This
evidence implies that a major release of sulfur
from the mantle occurred because of an extraterrestrial impact. Significant oxygen consumption and precipitation of strong acid rain
by an enormous release of sulfur from the
mantle would have caused the mass extinction
at this time and established the environment
that led to the subsequent origination of the
Holocene biota on Earth.
ACKNOWLEDGMENTS
We thank J.C. Ingle, B.M. Simonson, and an anonymous
referee for reviews. This work was partly supported by a
818
grant-in-aid for scientific research from the Ministry of Education, Science and Culture of Japan.
REFERENCES CITED
Alvarez, W., 1986, Toward a theory of impact crises: Eos
(Transactions, American Geophysical Union), v. 67,
p. 649, 653–655, 658.
Becker, L., Poreda, R.J., Hunt, A.G., Bunck, T.E., and Rampino, M., 2001, Impact event at the Permian-Triassic
boundary: Evidence from extraterrestrial noble gases
in fullerenes: Science, v. 291, p. 1530–1533.
Berner, R.A., 1980, Early diagenesis: A theoretical approach: Princeton, New Jersey, Princeton University
Press, 241, 118 p.
Bowen, R., 1988, Isotopes in the earth sciences: New York,
Elsevier, 647 p.
Bowring, S.A., Erwin, D.H., Jin, Y.G., Martin, M.W., David, E.K., and Wang, W., 1998, U/Pb zircon geochronology and tempo of the end-Permian mass extinction: Science, v. 280, p. 1039–1045.
Burke, W.H., Denison, R.E., Hetherington, E.A., Koepnick,
R.B., Nelson, H.F., and Otto, J.B., 1982, Variation of
seawater 87Sr/86Sr throughout Phanerozoic time: Geology, v. 10, p. 516–519.
Chen, Z.Q., Shi, G.R., Yang, W.R., and Tong, J.N., 1999,
Stratigraphy, sedimentology and palaeontology of the
Changhsingian and the Permian-Triassic boundary
beds in the Meishan section, Changxing, eastern China—A field excursion guide: Melbourne, Australia,
Deakin University, School of Ecology and Environment Technical Paper 1999/1, p. 1–68.
Claypool, G.E., Holser, W.T., Kaplan, I.R., Sakai, H., and
Zak, I., 1980, The age curves of sulfur and oxygen
isotopes in marine sulfate and their mutual interpretation: Chemical Geology, v. 28, p. 199–260.
Erwin, D.H., 1993, The great Paleozoic crisis: New York,
Columbia University Press, 327 p.
Erwin, D.H., 1994, The Permo-Triassic extinction: Nature,
v. 367, p. 231–236.
Eshet, Y., Rampino, M.R., and Visscher, H., 1995, Fungal
event and palynological record of ecological crisis
and recovery across the Permian-Triassic boundary:
Geology, v. 23, p. 967–970.
French, B.M., 1998, Traces of catastrophe: A handbook of
shock-metamorphic effects in terrestrial meteorite
impact structures: Houston, Texas, Lunar and Planetary Institute, Contribution 954, 120 p.
Grieve, R.A.F., Dence, M.R., and Robertson, P.B., 1977,
Cratering process: As interpreted from the occurrence
of impact melts, in Roddy, D.J., et al., eds., Impact
and explosion cratering: Planetary and terrestrial implications: New York, Pergamon Press, p. 791–814.
Holser, W.T., Schidlowski, M., Mackenzie, F.T., and Maynard, J.B., 1988, Biogeochemical cycles of carbon
and sulfur, in Gregor, C.B., et al., eds., Chemical cycles in the evolution of the Earth: New York, John
Wiley & Sons, p. 105–173.
Jin, Y.G., Wang, Y., Wang, W., Shang, Q.H., Cao, C.Q.,
and Erwin, D.H., 2000, Pattern of marine mass extinction near the Permian-Triassic boundary in south
China: Science, v. 289, p. 432–436.
Kaiho, K., and Lamolda, M.A., 1999, Catastrophic extinction of planktonic foraminifera at the CretaceousTertiary boundary evidenced by stable isotopes and
foraminiferal abundance at Caravaca, Spain: Geology, v. 27, p. 355–358.
Kaiho, K., Kajiwara, Y., Tazaki, K., Ueshima, M., Takeda,
N., Kawahata, H., Arinobu, T., Ishiwatari, R., Hirai,
A., and Lamolda, A., 1999, Oceanic primary productivity and dissolved oxygen levels at the Cretaceous/Tertiary boundary: Their decrease, subsequent
warming, and recovery: Paleoceanography, v. 14,
p. 511–524.
Kajiwara, Y., Sasaki, A., and Matsubaya, O., 1981, Kinetic
sulfur isotope effects in the thermal decomposition of
pyrite: Geochemical Journal, v. 15, p. 193–197.
Macdougall, J.D., 1988, Seawater strontium isotopes, acid
rain, and the Cretaceous-Tertiary boundary: Science,
v. 239, p. 485–487.
McEwing, C.E., Thode, H.G., and Rees, C.E., 1980, Sul-
phur isotope effects in the dissociation and evaporation of troilite: A possible mechanism for 34S enrichment in lunar soils: Geochimica et Cosmochimica
Acta, v. 44, p. 565–571.
Miura, Y., Fukuyama, S., and Gucsik, A., 1999, Impact
metamorphosed compositions of the Fe-Si-Ni-S system: Materials Processing Technology, v. 85,
p. 188–193.
Miura, Y., Fukuyama, S., Kedves, M.A., Yamori, A., Okamoto, M., and Gucsik, A., 2000, Chemical separation
of Fe-Ni particles after impact: Advances in Space
Research, v. 25, p. 285–288.
Popp, B.N., Podoser, F.A., Brannon, J.C., Anderson, T.F.,
and Pier, J., 1986, 87Sr/86Sr ratios in Permo-Carboniferous sea water from the analyses of well-preserved
brachiopod shells: Geochimica et Cosmochimica
Acta, v. 50, p. 1311–1328.
Prinn, R.G., and Fegley, B., 1987, Bolide impacts, acid
rain, and biospheric traumas at the CretaceousTertiary boundary: Earth and Planetary Science Letters, v. 83, p. 1–15.
Rampino, M.R., and Adler, A.C., 1998, Evidence for abrupt
latest Permian mass extinction of foraminifera: Results of tests for the Signor-Lipps effect: Geology,
v. 26, p. 415–418.
Renne, P.R., Zichao, Z., Richards, M.A., Black, M.T., and
Basu, A.R., 1995, Synchrony and causal relations between Permian-Triassic boundary crisis and Siberian
flood volcanism: Science, v. 269, p. 1413–1416.
Retallack, G.J., 1995, Permian-Triassic extinction on land:
Science, v. 267, p. 77–80.
Sakai, H., and Matsuhisa, Y., 1996, Stable isotope geochemistry: Tokyo, University of Tokyo Press, 403 p.
Sakai, H., Casadevall, T.J., and Moore, J.G., 1982, Chemistry and isotope ratios of sulfur in basalts and volcanic gases at Kilauea volcano, Hawaii: Geochimica
et Cosmochimica Acta, v. 46, p. 729–738.
Sakai, H., Des Marais, D.J., Ueda, A., and Moore, J.G.,
1984, Concentrations and isotopic ratios of carbon,
nitrogen and sulfur in ocean-floor basalts: Geochimica et Cosmochimica Acta, v. 48, p. 2433–2441.
Sheehan, P.M., Fastovsky, D.E., Barreto, C., and Hoffmann,
R.G., 2000, Dinosaur abundance was not declining
in a ‘‘3 m gap’’ at the top of the Hell Creek Formation, Montana and North Dakota: Geology, v. 28,
p. 523–526.
Sheng, J.Z., Chen, C.C., Wang, Y.G., Rui, L., Liao, Z.T.,
Bando, Y., Ishii, K., Nakazawa, K., and Nakamura,
K., 1984, Permian-Triassic boundary in middle and
eastern Tethys: Hokkaido University Journal of Faculty of Sciences, ser. 4, v. 21, p. 133–181.
Wang, C.Y., 1994, A conodont-based high-resolution eventostratigraphy and biostratigraphy for the PermianTriassic boundaries in South China: Palaeoworld,
v. 4, p. 234–248.
Yang, Z.Y., Yin, H.F., Wu, S.B., Yang, F.Q., Ding, M.H.,
and Xu, G.R., 1987, Permian-Triassic boundary stratigraphy and fauna of South China: Beijing, Geological Publishing House, Geological Memoirs, ser. 2 (6)
(in Chinese with English abstract).
Yin, H.F., Wu, S.B., Ding, M.H., Zhang, K.X., Tong, J.N.,
Yang, F.Q., and Lai, X.L., 1996, The Meishan section, candidate for the Global Stratotype Section and
Point of the Permian-Triassic boundary, in Yin, H.F.,
ed., The Palaeozoic-Mesozoic boundary candidates
for Global Stratotype Section and Point of the Permian-Triassic boundary: Wuhan, China University of
Geosciences Press, Natural Science Foundation of
China Project, p. 31–48.
Zhao, J.K., Sheng, J.C., Yao, Z.Q., Liang, X.L., Chen, C.C.,
Rui, L., and Liao, Z.T., 1981, The Changhsingian and
Permian-Triassic boundary of South China: Academia Sinica, Nanjing Institute of Geology and Palaeontology Bulletin, v. 2, p. 1–95 (in Chinese with
English abstract).
Manuscript received November 27, 2000
Revised manuscript received May 1, 2001
Manuscript accepted May 18, 2001
Printed in USA
GEOLOGY, September 2001