Table Of Content1
Introduction
1.1 Geological Questions
The Korean Peninsula consists of scenic mountains and valleys that run one after
another(Figures 1.1(cid:1)1.3).These features havedescendedfromcrustaldeformation
and the associated plutonic and volcanic activities. Rivers run through the valleys,
carrying sediments mostly toward the west and the south, forming floodplains.
Where the rivers meet the coastal plain, estuaries form. Along the western and
southern coasts of the peninsula, tidal flats are extensive, rivaling those of the
North Sea and the Bay of Fundy. The Yellow Sea is a shallow (55m on average)
epicontinental sea, surrounded by the landmass of China and Korea. Off the west-
ern and southern coasts of the peninsula, there are more than 3000 islands.
However, the eastern continental shelf is narrow and transitional to a bowl-shaped
deep basin, the Ulleung Basin, and the Korea Plateau, which are dotted by numer-
ous volcanic seamounts and islands, including the Ulleung and Dok islands
(Figure 1.4). The volcanic island of Jeju comprises a central crater, about 360 sco-
riacones,andtuffringsandcones.
The Korean Peninsula comprises denudation remnant of deformed basement
rocks and sedimentary successions, concealing a long history of crustal defor-
mation (Figure 1.5). Sedimentary rocks especially contain records of environ-
mental change through Earth’s history, including climate change, the rise and
fall of sea level, and the movement of tectonic plates over millions of years.
The peninsula presents a number of fundamental questions as to its origin and
dynamic processes. What constitutes the scenic mountains and ridges? When
and how did these mountain chains form? Was it due to the collision of the
tectonic plates? How often was the continent submerged under the sea through-
out Earth’s history? How are the rocks in the peninsula linked to those of
China and Japan? What are the origins of the deep basins and submarine pla-
teaus in the East Sea? How did the continent under the Yellow Sea form and
evolve? How would the coastal areas be affected by sea-level change over
timescales of a few decades to centuries? These are commonly asked questions
regarding dynamic processes and environmental changes of the Korean
Peninsula on land and under the sea.
GeologyandSedimentologyoftheKoreanPeninsula.DOI:http://dx.doi.org/10.1016/B978-0-12-405518-6.00001-2
©2013ElsevierInc.Allrightsreserved.
2 GeologyandSedimentologyoftheKoreanPeninsula
Figure1.1 Satelliteimageofthe
KoreanPeninsula.Thepeninsula
consistslargelyofmountains(about
65%).Thereareabout3000islandsoff
thesouthandwestcoasts.
Source:GOCI/COMSRGBColor
CompositeImageprocessedbyKorea
OceanSatelliteCenter/KoreaOcean
ResearchandDevelopmentInstitute.
1.2 Sedimentary Facies Analysis
Sedimentary rocks are important constituents (more than 50%) of the crust of
the Korean Peninsula. Sedimentary rocks (and sediments) are characterized by
grain size and sedimentary structures, i.e., sedimentary facies, defined as a
depositional unit characterized by a particular combination of grain size (lithol-
ogy) and sedimentary (physical and biological) structures (Figure 1.6). Each
unit of sedimentary facies represents distinct depositional processes that act on
the sediments in particular environments (Figure 1.7). Genetically related facies
can form a group, defined as a facies association or a sequence that has
some environmental significance. An analysis of sedimentary facies thus leads
the way to diagnosing depositional processes and environments (Dalrymple,
2010).
Sedimentary facies analysis is essential to the study of stratigraphy, which is
primarily concernedwith the recognitionofdistinct bodiesofrocks inachronolog-
ical framework. A lithostratigraphic unit is defined by its lithologic characteristics
instratigraphicpositionrelativetootherbodiesofsedimentaryrock.Asedimentary
rock unit can also be characterized by its fossil contents, biostratigraphy. Various
other methods have also been used to define stratigraphic units, including magne-
tostratigraphyandchemostratigraphy.
Introduction 3
Figure1.2 GeographicmapofSouthKorea.
Source:NationalGeographic(2003)bypermissionoftheNationalGeographicSociety.
4 GeologyandSedimentologyoftheKoreanPeninsula
(A)
(B)
(C)
Figure1.3 (A)View of a mountain chain in the southeast of Taebaek city, Gangwon
Province. The ridges comprise sedimentary rocks (limestone and sandstone) that
formed in shallow water environments during the Paleozoic (about 520(cid:1)250Ma)
and deformed in the Mesozoic (ca. 250(cid:1)150Ma). The mountains represent remnant
of continuous denudation for the last 150 million years. (B) Snow covered Wolak
mountain in the background. It consists of granite intruded into metasedimentary
rocks. (C) The meandering East River showing mid-channel and sidebars of
gravelly sands.
Sedimentary facies analysis leads to an understanding of controls on basin evo-
lution, including tectonics, climate changes, and sea-level changes (Miall, 2000,
2010). Plate movement causes subsidence of the crust, which provides the space
for the accumulation of sediments. Sedimentary basins are commonly formed
according to the plate tectonic regime: divergent, convergent, transcurrent, intra-
plate, and hybrid settings. Subsidence is induced by a thinning of the crust due to
stretching, erosion, and magmatic withdrawal as well as tectonic and sedimentary
loading and others (Busby and Azor, 2011). Uplift/subsidence also affects climate
changes and the amounts of sediment supply. Along with these factors, sea-level
changes control depositional processes and environments, especially in the shore-
lineandshallow waters.
Introduction 5
Figure1.4 TopographicreliefoftheKoreanPeninsulaandthenortheastAsianmargin.
Source:CourtesyofK.Tamaki.
Sedimentaryfaciesanalysiseventuallyleadstosequencestratigraphy,whichisthe
study of rock relationships within a chronostratigraphic framework of repetitive,
geneticallyrelatedstrataboundedbysurfacesoferosionornondeposition,ortheircor-
relativeconformities(Posamentieretal.,1988;Van Wagoneretal.,1990). Sequence
stratigraphicanalysisfocusesonthegeometriccharactersofstratalpatternsandidenti-
fications of key surfaces to determine the chronological order of basin fills
(Catuneanu,2006;EmeryandMyers,1996).Theunderlyingtenetofsequencestratig-
raphywasthatachangeinsealevelwouldresultinachangeinstratalpatterns,which
couldbecomparedamongbasinsworldwide.Thisdeductivegenericviewofsequence
stratigraphy has hampered, however, to further process-based sedimentological
approach to an integrated basin analysis. The high variability of bounding surfaces
and stratigraphic units requires inductive analysis for individual rock records
(Catuneanuetal.,2009,2010).Modernsequencestratigraphyfocusesonthechanges
instratalstackingpatternsinresponsetovaryingaccommodationandsedimentsupply
through time (Catuneanu et al., 2010; Miall, 2010). Attention is now given to the
specificsofhowstratalarchitecturecanthrowlightondepositionalprocessesandallo-
geniccontrols.
Over the past 30 years, extensive sedimentary facies analyses have been made
in major sedimentary basins of the Korean Peninsula, including the siliciclastics,
carbonates, and mixed siliciclastic(cid:1)carbonate successions as well as the nonmarine
6 GeologyandSedimentologyoftheKoreanPeninsula
N
41°
0 100
km
L E G E N D
ULLEUNG IS. SEDIMENTARY ROCKS
39° 38° DOK IS. TERTIARY YJAENOGNKILI G&RS.
131° YUCHEON GR.
NEUNGJU GR.
CRETACEOUS JINAN GR.
SINLA SER.
HAYANG GR.
E A S T
NAKTONG SER.
SINDONG GR.
S E A BANSONG &
JURASSIC DAEDONG GRS.
NAMPO GR.
S E O U L
NOGAM GR.
PERMIAN GOBANGSAN &
SADONG FMS.
DEV.-PERM. MANMO GR.
GEUMCHEON-
37° CARBONIFEROUS JANGSEONG FM.
MANHANG FM.
ORDOVICIAN- JOSEONG
CAMBRIAN SUPER GR.
Y E L L O W METAMORPHIC ROCKS
OKCHEON GR.
AGE UNKNOWN
S E A YULLI GR.
WONNAM GR.
SANGWON GR.
PRECAMBRIAN
YONCHON GR.
YONGNAM MASSIF
MACHONRYEONG
GR.
35° GMYAESOSINFGGI
IGNEOUS ROCKS
QUATERNARY B(TARSAACLHTYTE)
TERTIARY HYPABYSSAL &
VOLCANIC ROCK
MASANITE
CRETACEOUS BULGUGSA
S O U T H S E A GRANITE
JURASSIC DAEBO GRANITE
TRIASSIC GRANITE
INTERMEDIATE &
AGE UNKNOWN BASIC PLUTON
ANORTHOSITE
125° 127° 129° 131°
Figure1.5 GeologicmapoftheKoreanPeninsula.
Source:KoreaInstituteofEnergyandResources(1981)bypermissionoftheKoreaInstitute
ofGeoscienceandMineralResources.
Introduction 7
(A)
(B)
0 1m
Figure1.6 Sedimentaryfacies.(A)Bidirectionalcross-beddedsandstone,MantouFormation,
ShandongProvince,China.(B)Linedrawingoflarge-scalescouratthebaseofforeset.Thelower
leftpartischaracterizedbycrossstratified,disorganized,andopenworkamalgamatedbedsof
conglomeratessimilartoGilbert-typetopsetfacies.Theforesetischaracterizedbysteeplyinclined
bedsofstratifiedandinverselygradedconglomerates,DoumsanFanDelta,PohangBasin.
Alluvial fan Tidal flat
Submarine fan
Meandering river
Delta Shelf
Slope
Lake Beach
Braided river Basin
Offshore
Lagoon Biasrlrainedr carbonates
Reef
Figure1.7 Alarge-scaleviewofdepositionalenvironmentsonEarth’ssurface.
8 GeologyandSedimentologyoftheKoreanPeninsula
deposits. The results have led to significant advancement in the understanding of
depositional processes and environments as well as of dynamic crustal evolution
of the peninsula on land and under the sea. In this book, I summarize the results of
these works, focusingon the tectonic and sedimentary evolution and environmental
changesinviewoftheglobalevents.
2
Tectonic Setting
2.1 Basement Rocks
2.1.1 Introduction
The basement rocks of the Korean Peninsula consist of high-grade gneiss and
schist, Precambrian massifs, which formed in the early stage of Earth’s his-
tory (Figure 2.1). These rocks are unconformably overlain by metasedimentary
rocks (schist, quartzite, marble, calcsilicate, and amphibolite) of the Middle to
Late Proterozoic (Cho and Kim, 2005; Lee, 1987a). Subsidence of a large
sedimentary basin, subduction of a cooling plate, and obduction of colliding
plates can bury unconsolidated sediments and crystalline rocks to depths of
several tens of kilometers where metamorphic minerals form, including garnet,
kyanite, sillimanite, staurolite, and andalusite. Andalusite recrystallizes to
form sillimanite at low pressure or kyanite at high pressure. The presence of
one of these index minerals is indicative of a specific range of temperature
and pressure of mineral formation in the Earth’s interior. There are three
massif bodies in the Korean Peninsula, namely the Nangrim Massif in the
northern part and the Gyeonggi and Yeongnam massifs in the southern part
(Figures 2.1 and 2.2).
2.1.2 Nangrim Massif
The Nangrim Massif underlies the Pyeongnam Basin and bounds the microblocks
of Macheonryeong and Kwanmobong massifs (Figure 2.2). These blocks were
fused together in the Paleoproterozoic (Li et al., 2011; Lyang et al., 2009). The
entire massif consists of orthogneiss and granite gneiss and the overlying metasedi-
mentary units of the lower Nangrim and Musan groups and the upper Jeungsan
Group (Lower Paleoproterozoic) as well as the Hwanghae, Euiju, and
Macheonryeong groups (Neoproterozoic) (Lee and Cho, 2012). The Nangrim
Group consists of quartzite, marble, amphibolite, and biotite gneiss, and the inter-
layered hypersthene(cid:1)biotite gneiss, which formed at 2.7(cid:1)2.5Ga (Lee and Cho,
2012). The Jeungsan Group consists largely of crystalline schists of low-grade
metamorphism and weak granitization. The Euiju Group along the Aprok River
also consistsofcrystalline schist,intruded by rapakivi granite.In the Myohyangsan
area, it yields an age of 1861Ma (Zhai et al., 2007). The Hwanghae Group in the
southwestern part comprises metasedimentary rocks and volcanics, intruded by
GeologyandSedimentologyoftheKoreanPeninsula.DOI:http://dx.doi.org/10.1016/B978-0-12-405518-6.00002-4
©2013ElsevierInc.Allrightsreserved.
10 GeologyandSedimentologyoftheKoreanPeninsula
Figure2.1 MajortectonicfeaturesandstratigraphyoftheKoreanPeninsula.
granite (Lee and Cho, 2012). The Macheonryeong Group, formed along the bound-
ary between the Nangrim Massif and the Kwanmobong micromassif, consists
of thick dolostone, metavolcanics, and schist, which were intruded by
Paleoproterozoic granite (1847Ma) (Paek et al., 1996). The uppermost part of the
massif comprises the Sangwon Group in the Pyeongnam Basin and the Guhyun
Group (upper Mesoproterozoic(cid:1)Neoproterozoic). Age dates of granitic rocks and
gneisses of the massif using a sensitive high-resolution ion microprobe (SHRIMP)
and other methods at various localities (Myohyangsan, Gaesong, and others) yield
two age groups, namely 2.1Ga and 1.9(cid:1)1.8Ga (Lee and Cho, 2012; Song et al.,
2009;Wuetal.,2007;Zhaoetal.,2006)(Figures2.3and2.4).
