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circulation. Although the coral reef hypothesis

seems unlikely to explain the entire CO

shift be-

tween glacials and interglacials, the same mechanism

would have been more effective before the introduc-

tion of shelly plankton and before the establishment

of a CCD.

The causes of CH

changes are unlikely to be the

same as for CO

changes. The largest sources of CH

are the methane clathrate reservoirs that form be-

neath cold ocean floors at depths of several hundreds

of metres (Figure 7); on land, the CH

reservoirs are

in deep lakes or deep beneath the tundra floor in

Siberia, Greenland, and North America (see Petrol-

eum Geology: Gas Hydrates). Rising CH

levels

could represent a response to global warming in the

form of decomposition of these volatile methane res-

ervoirs, but whether on land, beneath the seafloor, or

beneath retreating glaciers is unclear. Because CH

unstable in the presence of oxygen and has a very

short half-life in the atmosphere (about 10 years),

any increase in CH

levels would translate eventually

into a more sustained increase in the CO

content of

the atmosphere.

Anthropogenically Induced CO

Increase and Future Predictions

Atmospheric CO

levels have been measured directly

since 1957 at Mauna Loa, Hawaii; these and other

data reveal that PCO

has risen by nearly 40%

since 1800, most of half of this rise occurring dur-

ing only the past half century (Figure 10). Ice-core

Figure 9 A qualitative comparison of CaCO

deposition and

erosion to and from carbonate reef platforms from interglacial

to glacial episodes. Reprinted from Milliman JD (1974) Marine

carbonates. In: Milliman JD, Mueller G, and Foerstner U (eds.)

Recent Sedimentary Carbonates, vol. 1. Berlin: Springer-Verlag.

Figure 10 The ‘Keeling’ curve. Measurements of monthly average atmospheric CO

concentrations at the top of Mauna Loa, Mauna

Loa Observatory, Hawaii. Source: CD Keeling and TP Wharf, Scripps Institute of Oceanography, La Jolla, California, USA (available on

theInternetathttp://cdiac.esd.ornl.gov/trends/co2/graphics/mlo144e.pdf).

CARBON CYCLE 343

measurements of trapped air demonstrate that PCO

for the 18 000 years before 1800 was much lower

than it is today, and consistently averaged 280 ppm.

There is a widespread agreement among scientists

that the almost 100-ppm rise since the beginning of

industrialization is unprecedented, being more than

the increase during the last interglacial warming,

which took place over thousands of years rather

than over a mere 200 years. Isotopic analyses of at-

mospheric CO

confirm beyond doubt that this extra

derives in large part from the incineration of

fossil fuels such as coal, oil, and gas.

The major components of the anthropogenic per-

turbation to the atmospheric carbon budget are

anthropogenic emissions, ocean and terrestrial ex-

changes, and their effects on the atmospheric CO

increase (Figure 11). Models suggest that each year

more than half of all the anthropogenic emissions

from fossil fuel combustion, cement production, and

tropical land clearing are offset by uptake in the

oceans, by forest regrowth largely in the northern

hemisphere, and by enhanced growth caused by in-

creased levels of nutrients, mostly CO

and nitrate

from fertilizers. Although several potential feedbacks

exist to further counteract CO

increase through the

effects of climate on ocean and terrestrial biosphere

uptake of CO

, it is not thought that these are signifi-

cant in the short term. However, the possible effects

of climate change on ocean circulation could be very

significant indeed.

Much current research is devoted to predicting

how CO

levels are likely to rise in the future and

what impact this will have on global climate, sea-

level, and biodiversity. The greenhouse effect of CO

is roughly logarithmic, which means that each factor-

of-two increase in CO

produces roughly the same

amount of warming. Global circulation models pre-

dict a doubling of CO

levels by the end of the

twenty-first century (Figure 12) associated with

global warming of between 1.5 and 4.5



C. Although

the effects of global warming will be felt worldwide,

changes in temperature will be distributed unevenly,

with by far the greatest impact felt in the high lati-

tudes of the northern hemisphere. Because the cycling

of carbon in the terrestrial and ocean biospheres

occurs slowly, on time-scales of decades to millennia,

the effect of additional CO

through industrialization

inevitably represents a long-lasting disturbance to the

carbon cycle. Model predictions of future atmos-

pheric CO

levels indicate that they will continue to

Figure 11 Major carbon reservoirs and fluxes (in gigatons and gigatons year

1

, respectively) in the global anthropogenically

influenced carbon cycle. Reprinted from Kump LR, Kasting JF, and Crane RG (1999)

The Earth System. Upper Saddle River, NJ:

Prentice Hall.

344 CARBON CYCLE

rise throughout the present century, even if emissions

are held constant. If the level at which CO

stabilizes

is kept below 750 ppm, almost three times preindus-

trial levels, emissions will still have to be cut relative

to today’s emission rates.

p9000 There is continual improvement in our understand-

ing of the modern-day carbon cycle, and increasingly

sophisticated models are being developed to describe

the Earth system (see Earth System Science). How-

ever, it is already clear that we have begun an unpre-

cedented experiment, the course of which we cannot

control over the short-term, but which will shortly

become clear.

Further Reading

Berger WH (1982) Increase of carbon dioxide in the at-

mosphere during deglaciation: the coral reef hypothesis.

Naturwissenschaften 69: 87–88.

Berner RA (1992) Weathering, plants and the long-term

carbon cycle. Geochimica et Cosmochimica Acta 56:

3225–3231.

Gaillardet J, Dupre

B, Louvat P, and Alle

gre CJ (1999)

Global silicate weathering and CO

consumption rates

deduced from the chemistry of the large rivers. Chemical

Geology 159: 3–30.

Katz ME, Pak DK, Dickens GR, and Miller KG (1999) The

source and fate of massive carbon input during the Latest

Paleocene Thermal Maximum. Science 286: 1531–1533.

Kump LR, Kasting JF, and Crane RG (1999) The Earth

System. Upper Saddle River, NJ: Prentice Hall.

Pavlov AA, Kasting JF, Brown LL, Rages KA, and

Freedman R (2000) Greenhouse warming by CH

the atmosphere of early Earth. Journal of Geophysical

Research 105: 11981–11990.

Royer DL, Berner RA, and Beerling DJ (2001) Phanerozoic

atmospheric CO

change: evaluating geochemical and

paleobiological approaches. Earth Science Reviews 54:

349–392.

Sunquist ET and Broecker WS (1985) The Carbon Cycle and

Atmospheric CO

. American Geophysical Monograph

32. Washington, DC: American Geophysical Union.

Wigley TML and Schimel DS (eds.) (2000) The Carbon

Cycle. Cambridge: Cambridge University Press.

CHINA AND MONGOLIA

H Wang and Shihong Zhang, China University of

Geosciences, Beijing, China

Guoqi He, Peking University, Beijing, China

Introduction

China and Mongolia are among the most composite

in geological structures in the Asian countries. The

tectonic units of different ranks comprise tectonic

domains, platforms, and massifs with Precambrian

basement, and Phanerozoic orogenic belts and

zones. A tectonic domain usually encloses a

platform (craton) and its surrounding orogenic belts,

which are composed of orogenic zones of various

ages and interstitial Precambrian median massifs.

In the outline tectonic map of Asia (Figure 1), are

shown the main cratons, the major massifs, the

orogenic belts, and the major sutures of various

ages. The history of crustal evolution may be subdiv-

ided into tectonic megastages based on fundamental

Figure 12 Accumulated anthropogenic CO

emissions over a

period beginning in 1990 and projected out to 2200 (in gigatons of

carbon), plotted against the final stabilized concentration level.

Reprinted from Wigley TML and Schimel DS (eds.) (2000)

The

Carbon Cycle

. Cambridge: Cambridge University Press.

CHINA AND MONGOLIA 345

changes of tectonic frame of continental and even

global scale, and tectonic stages marked by pro-

nounced changes of widespread tectonic regimes,

during which revolutionary orogenic epochs of short

duration and rapid changes may be recognised

(Figure 2). The global stratigraphic chart used

follows the International Stratigraphic Chart (2000)

with some changes in the Precambrian part. The

tectonic development of China and Mongolia are

discussed in terms of the megastages and the main

geologic events that occurred in the various

orogenic epochs. Emphasis are put on the Neoproter-

ozoic Jinningian and the Upper Triassic Indosinian

orogenies in China and on the Palaeozoic Salairi-

an and Hercynian in Mongolia. The terms ‘Caledo-

nian’ and ‘Hercynian’ for orogenies in China have

different usages from their original locations in

Europe. A world palaeocontinental reconstruction

map for the Pangaea in mid-Permian time (Figure 4)

is presented to show the possible position of the

component parts of China and Mongolia and the

world floral provinces at that time.

The Geology of China

The Main Tectonic Units and Crustal

Evolution of China

The main tectonic units of China comprise three prin-

cipal continental platforms (cratons), Sino-Korea,

Yangtze, and Tarim, a deformed palaeocontinent

(Cathaysia), and orogenic belts of various ages. The

orogenic belts are situated between the platforms and

Figure 1 Simplified tectonic map of Asia.

Color

Image

346 CHINA AND MONGOLIA

major massifs, and contain small massifs that were

probably split from neighbouring palaeocontinents.

The plate boundary does not lie at the platform border

but in a demarcation zone between the once distantly

opposite marginal tracts of the palaeocontinents.

We have called the major crustal sutures, or the de-

marcation zones that represent the consumed open

seas, convergent crustal consumption zones (CZ),

and the sutures that represent accreted island

arcs onto the palaeocontinents, accretional crustal

consumption zones (AZ).

Geologically, three main regions may be recognised

in China. The northern region comprises the narrow

Altai-Arguna Belt representing the southernmost part

of the wide southern continent marginal tract of

Siberia Platform, and the Tianshan-Xingan Belt rep-

resenting the northern continent marginal tract

of Tarim (TAP) and Sino-Korea (SKP) platforms.

Figure 2 Tectonic megastages and geoevents in China and Mongolia.

CHINA AND MONGOLIA 347

The middle region consists of TAP and SKP, the Qilian

Caledonides between them, and the Kunlun-Qinling

Belt, the central orogenic belt of China, which is

mainly composed of the Indosinides. The southern

boundary of this region is the Indosinian Muztagh-

Maqen convergent zone (MMCZ) in the west and

the superimposed Indosinian Fengxian-Shucheng

convergent zone (FSCZ) in the east. The southern

region includes two parts: the eastern part, South

China, consists of the Yangtze Platform (YZP), the

Cathaysia palaeocontinent (CTA), and the Caledo-

nides and Indosinides between them, while the west-

ern part covers the Qinhai-Tibet Plateau and the

broad Indosinides to the south of MMCZ.

The history of crustal evolution of China may be

subdivided into five megastages: (i) continental nu-

cleus formation (ca. 2.7–2.8 Ga); (ii) protoplatform

formation (ca. 1.9–1.8 Ga); (iii) platform formation

(ca. 0.85–0.8 Ga); (iv) Laurasia Supercontinent or

Pangaea formation (ca. 230–210 Ma); and (v) intra-

continental development (210 Ma-Present) (Figure 2).

Two orogenic epochs of revolutionary changes oc-

curred in the Jinningian (ca. 1000–830 Ma) and the

Indosinian (ca. 230–210 Ma). The close of the Jinnin-

gian Orogeny probably witnessed a convergence of

the Chinese platforms and massifs to form the super-

continent of Cathaysiana, which was a part of the

Neoproterozoic Rodinia (850 Ma). After the close of

the Indosinian Orogeny, the tectonic frame of China

underwent a basic change from a contrast between the

north and the south to that between the east and the

west. Thus, the crustal evolution of China underwent

three stages; (i) the Jinningian and pre-Jinningian

(Archaean to Early Neoproterozoic >800 Ma); (ii)

the post-Jinningian to the Indosinian (Nanhuan to

Triassic); and (iii) the post-Indosinian (Jurassic to

Quaternary) (Figure 2).

China in the Pre-Jinningian and Jinningian

(Archaean to Qingbaikouan)

The time span from Archaean to Early Neoprotero-

zoic (ca. 800 Ma) may be subdivided into three mega-

stages which resulted respectively in the formation

of continental nuclei at the end of the Mesoarchaean

(ca. 2.8 Ga), the formation of protoplatforms at

the end of the Palaeoproterozoic (ca. 1.8 Ga) through

the Luliangian Orogeny, and the formation of plat-

forms at the end of the Early Neoproterozoic

(ca. 800 Ma) through the Jinningian Orogeny.

The continental nuclei Several continental nuclei

may be recognized in SKP, by the presence of

Mesoarchaean and older metamorphic supracrustal

and TTG rocks. The Jiliao Nucleus (Jl) encloses north-

ern Shanxi, northern and eastern Hebei, northern

Liaoning and Jilin provinces (Figure 3). U-Pb and Pb-

Pb ages of 3850–3550 Ma, representing the Eoarch-

aean primordial sialic crust and supercrustals, were

identified from Caozhuang, eastern Hebei, and

Anshan, Liaoning. Mesoarchaean rocks older than

2.8 Ga are known from the Jiaodong Nucleus (Jd) in

eastern Shandong, the Sanggan gneiss, the Jining

Nucleus (Jn) in the southern Inner Mongolia, and

northern Shanxi. The Ordos Nucleus (Or) is inferred

to exist under the northern part of the Ordos basin

based on geophysical as well as geological data.

Further in the west is the small Alxa Nucleus (Ax)

near the western border of SKP.

In the Yangtze Platform (YZP), Mesoarchaean

TTG rocks older than 2.8 Ga are known from the

Kongling Group in the Yangtze Gorges region, prob-

ably representing the uplifted eastern margin of

the Chuanzhong Nucleus (Cz) beneath the Sichuan

basin. In the eastern part of the Tarim Platform

(TAP), Mesoarchaean rocks are reported from the

Quruktagh Nucleus (Qr) and from the Dunhuang

Nucleus (Dh), where a single grain zircon U-Pb age

of 3.6 Ga of Eoarchaean age was recently obtained.

Generally, these ancient continental nuclei are distrib-

uted in the northern part of SKP and the north-eastern

part of TAP. It is noteworthy that isotopic model age

studies for various Archaean rocks in the SKP show a

cluster around 2.8–2.7 Ga, which denotes an epoch of

rapid continental growth, as in many other cratons

in the world.

The Protoplatforms and the Luliangian Orogeny

The Neoarchaean is widely distributed in the

platform regions of China, especially in SKP. The

juvenile crust generated in the Neoarchaean may be

mostly assigned to the granite-greenstone terrains

with a high proportion of granitoid intrusives, as in

the Taishan Complex in Shandong. The Neoarchaean

usually occurs as granite and TTG belts around and

within the reworked nuclear regions in SKP. On the

other hand, Neoarchaean greenstone belts, repre-

sented by the Wutai, Dengfeng and Taihua groups in

Shanxi and Henan, contain more khondalites and

mafic volcanics, and are probably of extensional

origin. In general, the Neoarchaean witnessed a pro-

fuse intrusive and extrusive magmatism of 2.6–2.4 Ga

age throughout SKP, which is responsible for the

formation of united Archaean basement.

The Palaeoproterozoic (Pp) in SKP, generally called

the Hutuoan ‘System’ (2500–1800 Ma), often occurs

in long narrow belts and represents ancient aula-

cogens formed on the Archaean basement. The aula-

cogen sequence is mainly composed of a lower fluvial,

a middle immature volcanisedimentary, and an upper

molasse deposits. This sequence occurs in the Hutuo

348 CHINA AND MONGOLIA

and Gantaohe aulacogens in the Wutai-Taihang

region, in the Qinglong Aulacogen in north-eastern

Hebei, in the Liaohe and Fenzishan aulacogens in

eastern Shandong and southern Liaoning (Figure 3).

Through the Luliangian Orogeny of 1.9–1.7 Ga

age, these aulacogen rocks were intensely folded and

regionally metamorphosed, sometimes to a high

chlorite schist facies.

The Luliangian Orogeny brought about the forma-

tion of a protoplatform in North China, upon which

was deposited the Meso- and Neoproterozoic para-

cover. This orogenic event is also seen in the TAP and

Qaidam Massif (QD), where the Mesoproterozoic

and Neoproterozoic sequences are always separated

from the basement by a fragmented unconformity.

In YZP, the Palaeoproterozoic basement is probably

Figure 3 Outline map showing the tectonic units and crustal evolution of China. Hercynian and Yanshanian granites are wide spread

and planar in distribution, and are not shown on the map.

Tectonic units: AG, Arguna Massif; Ax, Alxa Nucleus; BT, Baoshan-Tengchong Massif; Ch, Chuanzhong Nucleus; CTA, Cathaysia

palaeocontinent; Dh, Dunhuang Nucleus; GD, Gangdise Massif; HM, Himalaya Massif; Jd, Jiaodong Nucleus; JG, Junggar Massif; JK,

Jamus-Xingkai Massif; JI, Jiliao Nucleus; Jn, Jining Nucleus; Kr, Kuruktagh Nucleus; LS, Lanping-Simao Massif; NQ, North Qiangtang

Massif; Or, Ordos Nucleus; QL, Qilian Massif; QM, Qamdo Massif; SB, Songpan-Bikou Massif; SCS, South China Sea Massif; SKP,

Sino-Korea Platform; SN, Songnen Massif; SQ, South Qiangtang Massif; TAP, Tarim Platform; XL, Xilinhot Massif; YN, Yining Massif;

YZP, Yangtze Platform; ZY, Zhongza-Yidun Massif.

Crustal consumption convergent zones (CZ):

JSCZ, Jiangshan-Shaoxing (Jinningian); QQCZ, Qilian-Qinling (Caledonian);

SQCZ, South Qilian (Caledonian); STCZ, South Tianshan (Hercynian); EACZ, Ertix-Almantai (Hercynian); HGCZ, Hegen-

shan (Hercynian);

MMCZ, Muztagh-Maqen (Indosinian); FSCZ, Fengxian-Shuchang (Indosinian); YZCZ, Yarlung-Zangbo

(Himalayan).

Accretional zones (AZ): WKAZ, West Kunlun (Jinningian); EKAZ, East Kunlun (Jinningian); KDAZ, Kudi (Indosinian); OSAZ,

Ondur Sum (Caledonian); NTAZ, North Tianshan (Hercynian); JSAZ, Jinshajiang (Indosinian); CMAZ, Changning-Menglian

(Indosinian);

BNAZ, Bangong-Nujiang (Yanshanian); LJCZ, Liji (Himalayan).

Strike-slip faults: Altun, Tanlu, Red River.

Color

Image

CHINA AND MONGOLIA 349

present to the south of the Chuanzhong Nucleus (Ch),

and the Kangdian belt in western YZP is mainly com-

posed of Palaeoproterozoic metamorphic rocks. In

CTA, Neoarchaean and Palaeoproterozoic rocks,

with Luliangian metamorphism of amphibolite facies,

occur in western Zhejiang and in the Wuyi Mountains

in north-western Fujian.

The platforms and the Jinningian Orogeny In SKP,

the Mesoproterozoic and Early Neoproterozoic

strata are widespread and are divisible into the

Changchengian (Ch), the Jixianian (Jx), and the Qin-

baikouan (Qb) ‘systems’. They are generally correla-

table through acritarch and stromatolite assemblages

between the main platforms of China. In the Yan-

shan-Taihang region, aulacogen (Figure 3) deposits

consisting of the Lower Changchengian fluvial

clastics, carbonates, and high potassium volcanics,

are followed by the widely transgressive Gaoyuz-

huang carbonates bearing the macro-alga Grepania

in the upper part (1.5–1.4 Ga). The Jixianian is also

widespread and contains stromatolite carbonates of

great thickness. The Qingbaikouan represents a plat-

form cover and is limited in distribution. The macro-

algal assemblages of the Jixianian Grepania and the

Qingbaikouan Tawuia-Longfengshania Assemblages

(900–800 Ma) are almost identical to those found in

the Greyson Shales in Montana and in the Little Dal

Formation in the McKenzie Mountains in the Belt

Supergroup of western North America. The Tawuia

beds are also found in Hainan Island, which was prob-

ably a part of the Cathaysia palaeocontinent. These

indicate that Laurentia and the Chinese palaeoconti-

nents may have been near each other during Meso- and

Neoproterozoic times.

Most platforms and massifs in China were do-

minated by an extensional tectonic regime in the

Meso- and Neoproterozoic, as shown by the Xionger

Aulacogen, with bimodal eruptives in Henan and

southeastern Shanxi, and the Bayan Obo Aulacogen

near the northern margin of SKP. Aulacogens of simi-

lar age are also developed in the Quruktagh region of

northern TAP and in the Kunming region of south-

western YZP. All these aulacogens ended without

any diastrophism. On the southern margin of SKP,

there may have developed an island-arc system

with the Qinling Group as the arc and the Kuanping

Group as the back-arc basin. Both groups yield

Mesoprotrozoic isotopic ages.

The Jinningian Orogeny of ca. 1000–830 Ma age

has left clear records in many parts of China. The

Qinling region, mainly South Qinling, was character-

ized by a complicated rift system probably formed in

Late Mesoproterozoic to Early Neoproterozoic,

which consisted of discrete massifs (Douling, Fuping)

and trough deposits with bimodal volcanicism (e.g.,

the Xixiang group). The Jinningian Orogeny is repre-

sented by island arcs and marginal seas in the south-

ern margin of North Qinling by the Songshugou

ophiolite (983 Ma) and by an Early Neoproterozoic

granite zone (e.g., the Dehe granite of ca. 950 Ma),

denoting a northward subduction and accretion

through an arc-continent collision. A similar south-

ward accretion, with subduction-type granites is also

found in the Hanzhong area of YZP. The common

cover of the Sinian over the rifted elements implies the

presence of a united South Qinling Belt. Therefore,

the Jinningian Orogeny brought about the consoli-

dation of the rifted region and the mutual approach

of SKP and YZP.

Along the south-western margin of YZP in central

Yunnan, to the east of the Early Mesoproterozoic

Dahongshan metamorphic volcanisedimentary Belt,

was developed a broad aulacogen trending north–

south for hundreds of kilometres, composed mainly

of the Mesoproterozoic Kunyang Group and equiva-

lent strata of huge thickness. These rocks were in-

tensely folded and intruded by the Jinningian granites

(850–750 Ma), and may be interpreted as a wide back-

arc basin lying to the east of the Dahongshan arc belt

in central Yunnan.

In the Jiangnan uplift along the south-eastern

margin of YZP, deformed arc-type turbidites with

ophiolite me

lange and Adakite zones dated at ca.

970 Ma represent an arc-continent collision of Early

Jinningian age. In fact, the Jinningian orogenic zone

was charaterized by volcanisedimentaries and gran-

ites extending from northern Zhejiang right to the

border area between Hunan and Guangxi. At

the close of the Jinningian Orogeny, a partial collision

between YZP and CTA occurred along the Jiangshan-

Shaoxing convergent zone (JSCZ), which closed at

around 830 Ma. The ocean basin between YZP and

CTA was probably separated by an archipelagic belt

composed of small massifs near the Hunan-

Jiangxi border. The north-western margin of CTA in

the Neoproterozoic was also active and extends from

Wuyi in North-western Fujian to Hainan Island.

Jinningian granites are distributed along the south-

ern margin of TAP and the Qaidam Massif in the

northern Kunlun Mountains and are also found in

the northern margin of Qaidam. These granite zones

represent active continental margins or continent-arc

collision zones (Figure 3). The Jinningian granites are

seldom found to the east of East Qinling, except in

eastern Shandong along the Sulu Belt, although a

Jinningian metamorphic event is suspected to be

represented by the Dabie UHP belt. In summary, the

main platforms and massifs in China seemed to have

converged to form a loosely united Cathaysiana

350 CHINA AND MONGOLIA

Supercontinent at around 850 Ma, concurrently with

the formation of the Neoproterozoic Rodinia.

China in the Post-Jinningian to the Indosinian

(Nanhuan to Triassic)

ThetimespanfromtheNanhuantotheTriassic

(800–208 Ma) is traditionally subdivided into

Caledonian, Hercynian, and Indosinian stages. The

traditional Sinian (800–543 Ma) is subdivided into

the Nanhuan (800–620 Ma) and the revised Sinian

(620–543 Ma) according to the new Regional Chron-

ostratigraphical Chart of China published by the Third

All-China Stratigraphical Commission in 1999. The

Hercynian and Indosinian are here integrated and

called the Hercynian-Indosinian Stage (Figure 2).

The Caledonian stage The Caledonian in China is

usually subdivided into a lower division of Xingkaian

(Salairian) covering the Nanhuan and the Sinian, and

an upper division covering the Middle Cambrian to

the Silurian. The Caledonides are mainly distributed

in the Qilian Mountains region between SKP and the

Qaidam Massif and in South China between YZP and

CTA. They are also found to the north of SKP and

TAP (Figure 3).

The Nanhuan in YZP is characterized by clastic,

glaciogenic, and cold-water deposits roughly corres-

ponding to the Cryogenian in the International Str-

atigraphic Chart. Continental ice-sheets of ca.

740–620 Ma age seem to have been confined to west-

ern YZP and the Quruktagh region of TAP, but

mountain and maritime glaciations are more wide-

spread. In the type region of the Yangtze Gorges in

the YZP, the Sinian includes the Doushantuo cap car-

bonates, phosphate and black shales bearing the

Miaohe or Wengan biota (Pb-Pb isotopic age ca.

600 Ma), and the Dengying Formation bearing the

Ediacara biota (ca. 590 Ma). In SKP, only the Sinian is

developed in the peripheral parts and bears a rich

metazoan fauna comparable with the Ediacara in

northern Anhui. A higher Luoquan glacial horizon

was reported all along the south-western border of

SKP, the northern border of Qaidam Massif, the north-

ern TAP and the Tianshan regions: it is probably

younger than 600 Ma in age.

In most parts of eastern China, the Lower Palaeo-

zoic began with an Early Cambrian transgression

from southern YZP to SKP, with well-established

trilobite zones for correlation. This indicates that

the two platforms were not far from each other, al-

though rifting seems to have begun in the Sinian, as is

shown by entirely different Nanhua-Sinian sequences

between the two platforms. The Early Cambrian

Chengjiang Lagerstatte (ca. 525 Ma), of great signifi-

cance in life evolution, contains arthropods and

chordates, especially Haikouichthys, which might be

the ‘first fish’ on Earth. No obvious break is known

between the Sinian and the Cambrian, especially

in South China, where bathyal carbonaceous silico-

lites are continuous in central Hunan and western

Zhejiang. The continuous Lower Palaeozoic passive

margin bathyal deposits have provided seldom seen

complete sequences of Cambrian agnostid trilobite

zones and Ordovician to Silurian graptolite zones,

which are ideal for the designation of chronostrati-

graphical boundaries. In the residual sea between

YZP and CTA, rifted uplifts and troughs were de-

veloped in which varied kinds of sediments were

laid down. The marine realm began to shrink in the

Late Ordovician, and the Caledonian Front, which

started in the Wuyi Mountains, seems to have shifted

westward, until the thick foreland basin deposits of

Early Silurian age were formed within the YZP in

westernmost Hunan. Caledonian granites and meta-

morphism are scattered, and no clear collision zone is

found in the broad Caledonides in South China,

which were ‘filled up’, rather than folded orogenic

zones. In southern Hainan Island, Cambrian trilo-

bites of Australian affinity are found, which may

represent the northern margin of SCS (Figure 2),

probably still far away to the south at that time.

The Caledonides between SKP and Qaidam on

both sides of the Central Qilian Massif (QL) are

represented by distinct collision belts and associated

granite zones. In North Qilian a complete Caledonian

orogenic sequence developed composed of Cambrian

and Ordovician island arc volcanics, Middle and

Upper Ordovician and Lower Silurian ophiolite

suites, and Devonian molasse deposits. The QQCZ

(Figure 4) is prominent and continues south-

eastwards into North Qinling. Late Cambrian ophio-

lite me

langes are also found in Lajishan in South

Qilian, which may connected to the SQCZ. The SKP

generally lacks the Upper Ordovician and Silurian

except in the western margins, and is bordered to

the north by a narrow Caledonide strip (south of

OSAZ), composed of Cambro-Ordovician metavol-

canics unconformably overlain by fossiliferous Silur-

ian sediments. Caledonides are also known around

the Junggar and Yining massifs in northern Xinjiang.

In TAP, the Cambrian and Ordovician are of platform

cover type, but display a slope and deep-sea facies in

the Manjiar depression in the eastern part. The Silur-

ian is incomplete and limited in distribution. Stable

Lower Palaeozoic deposits reported from Himalaya,

northern Gangdise, and north-western Qiangtang in-

dicate the existence of Precambrian basement in these

massifs. However, the age of the basement may be

as young as ca. 600 Ma, comparable with the

Pan-African of Gondwanaland.

CHINA AND MONGOLIA 351

Laurasia Supercontinent and the Hercynian-

Indosinian stage In the Late Palaeozoic, the major

part of SKP remained exposed after its upheaval in

mid-Ordovician, until the Middle Carboniferous epi-

continental seas began to inundate the platform.

Marine facies prevailed up to the mid-Permian and

are followed by Permo-Triassic paralic and terrestrial

deposits. A Devonian oceanic basin existed along the

China-Mongolia border, which was consumed and

formed the main Hercynian HGCZ. The orogenic

collision is manifested by Devonian to Early Carbon-

iferous ophiolites and Permian A-type granites which

mark the boundary between the Siberian continent

marginal tract in the north and the Sino-Korean mar-

ginal tract in the south. In northern Xinjiang, the

Hercynian EACZ is composed of en echelon su-

tures and represents the main boundary between the

Altai-Hingan and the Tianshan-Inner Mongolia belts,

and is continuous across southern Mongolia with

the HGCZ. Two Hercynian collision zones docu-

mented by ophiolites occur to the south of the

Junggar-Turpan and Yining massifs.

The Late Hercynian-Early Indosinian belts south of

Beishan in the west, and extending via Linxi to

Changchun in the east, are composed mostly of shal-

low marine and paralic sediments with occasional

volcanics. The eastern segment is a clear boundary

between the Angaran and the Cathaysian floras,

but no ophiolite me

langes have been found. These

marine troughs were probably filled at the end of

the Palaeozoic, and are not genuine orogenic zones.

Late Permian to Early Triassic terrestrial basins,

formed after the Hercynian Orogeny, are widespread

in northern Xinjiang, Gansu, and Inner Mongolia,

and bear the tetrapod remains of Dicynodon,

Lystrosaurus, and Sinokanemeyeria.

In the Late Palaeozoic, YZP was characterized in

its northern marginal tract, the South Qinling, by

thick Devonian continental slope flysch and marine

to paralic Carboniferous to Triassic clastics and car-

bonates. To the south, both YZP and CTA witnessed

Devonian transgressions from the residual Youjiang

marine basin, and Late Carboniferous and Permian

carbonate platforms were well developed in both

regions. Extensional conditions prevailed in YZP,

as is shown by the Late Permian Emei continental

flood basalt. Devonian to Triassic aulacogens with

different trends are known in south-western YZP,

and isolated carbonate platforms were formed in the

Youjiang oceanic basin, where Upper Palaeozoic

deep-sea deposits with pelagic radiolarians are

formed. The Youjiang marine basin was not closed

until the Late Triassic, when the Indosinian Orogeny

was predominant in most parts of southern China.

The eastern part of YZP, now partly submerged

under the sea, collided with SKP along the Dabie-

Sulu HP and UHP zone through the Indosinian

Orogeny, and was probably wedged in eastern SKP,

with its northeastern promontary along the Im-

qingang Belt in Korea. Orogenic and post-orogenic

Indosinian granite zones are widely distributed in

southern China and in the Kunlun-Qinling Belt.

Post-orogenic muscovite/two mica granites are

known to the north of SKP as a result of intraconti-

nental northward compression of SKP toward Inner

Mongolia (Figure 3).

Figure 4 A mid-Permian world palaeocontinental reconstruction.

Color

Image

352 CHINA AND MONGOLIA

Elsevier Encyclopedia of Geology - vol I A-E

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