STRUCTURE AND STRATIGRAPHY OF CHINA BASIN

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP08C01297R000200130010-7
• Release Decision: RIFPUB
• Original Classification: K
• Document Page Count: 17
• Document Creation Date: December 22, 2016
• Document Release Date: September 12, 2012
• Sequence Number: 10
• Publication Date: May 1, 1972
• Content Type: MISC

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Declassified and Approved For Release 2012/09/12 : CIA-RDP08001297R000200130010-7 r
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The American Association ol Petrdeum Geologists &Min
Y. 56, No. 5 (May 19721 P.839-859, II Figs.
a
Structure and Stratigraphy of China Basin'
Abstract Continuous seismic reflection profiles ac-
companied by total-field magnetic measurements
were made in the China basin by civilian survey ships
on contract to the U.S. Navy Oceanographic Office
between 1967 and 1969. The results show the pres-
ence of stratigraphic units similar to those previously
found in the adjacent East China Sea and South China
Sea: (1) acoustic basement in the southern part of the
basin that may be a continuation of the igneous and
metamorphic rocks beneath the adjacent shelf which
were peneplaned during Late Cretaceous-early Ceno-
zoic time, and much more irregular basement in the
northern part of the basin that may be oceanic base-
ment (Layer 2); (2) predeformational sediment, con-
formably with the surface of much of the acoustic
,* basement (probably Paleogene); and (3) postdeforma- ?
tional sediment, largely turbidites deposited in deeper
areas (probably Neogene to present) after the main
episode of deformation. During the deformation a se-
ries of northeast-trending ridges was folded along the
floor of the China basin. Similar ridges underlie the
. basin side slopes, and these served as dams to trap
sediments brought to the ocean by streams from the
adjacent land areas. Another ridge separates the Ma-
nila Trench and the West Luzon Trough, and extends .
northeastward as the Central Range of Taiwan. Oil -,
potential appears to be greatest beneath the shelf
between Taiwan and Hainan off mainland China, but
the basin ridges that are surmounted by banks and -
islands also warrant further investigation.
INTRODUCTION
? Since 1960 there has been a general increase of
geologic interest in the continental margin along
eastern Asia. Studies of sediments, stratigraphy,
and structure have bordered or included parts of
the China basin (Fig. 1), a large depression bor-
dered clockwise by Taiwan, Philippine Islands,
Borneo, Vietnam, Hainan, and mainland China
? (Fig. 2). Sediments of the shelf north of the China
' basin were described by Niino and Emery (1961),
and of the shelf southwest of it by Emery and
' Niino (1963). In both areas the sediments were .
considered as chiefly relict from glacially lowered
sea level and typical of the outer parts of most
continental shelves of the world. An advance in
the knowledge of the structure of the region came
from broad reconnaissance seismic and magnetic
surveys, first in the East China Sea (Emery et a/.,
1969; Wageman et al., 1970) and then in the
South China Sea (Parke et al., 1971) and in the
Java Sea (Emery et al., in press). Each of these
geophysical studies showed the presence of tec-
tonic ridges that served as submerged dams to
trap sediments derived from adjacent lands. Only
. 839
?
?
'r K. 0. EMERY2 and ZVI BEN-AVRAHAM2
Woods Hole, Massachusetts 02543
a
EAST ?
CHINA ?
SEA
?
o??
CHINA
BASIN
JAVA SEA
O.
90.
t00.
110.
no. 130.
1;06
FIG. I ?Outlines of areas investigated in this and previous
studies of China basin. Letters on land areas from north to
south: K, Korea; T, Taiwan; P.1., Philippine Islands; M, Malay
Peninsula; S, Sumatra; B, Borneo; N.G., New Guinea; J, Java.
after several million cubic kilometers of Cenozoic
sediments had accumulated in basins behind the
dams were sediments able to escape in quantity
over the dams and build thick sequences on the
floor of the deep ocean or the China basin.
'Manuscript received, September 9, 1971; accepted, Novem-
ber 10, 1971. Woods Hole Oceanographic Institution Contribu-
tion No. 2218.
1Woock Hole Oceanographic Institution.
Appreciation is due the U.S. Naval Oceanographic Office
through the interest of M. L. Parke, Jr., and L. M. Reynolds by
providing the microfilms and other field records needed for this
study. Copies of the seismic data are now available at the
National Geophysical Data Center, and copies of the magnetic
data are in the Magnetics Library, Naval Oceanographic Office.
Financial support was provided by the National Science Foun-
dation (Grant GA-27449) and the Office of Naval Research
(Contract N00014-66-0O241). This is one of a series of geophys-
ical studies conducted off eastern Asia in support of the United
Nations Economic Commission for Asia and the Far East, and
particularly of its Committee for Co-ordination of Offshore
Prospecting.
0 1972. The American Association of Petroleum Geologists All rights
reserved.
Declassified and Approved For Release 2012/09/12 : CIA-RDP08001297R000200130010-7
840 K. 0. Emery and Zvi ben-Avranam
110?
? ????
tructure ana 3iratigrapny OF l,11111d Da5Tri
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it tne CIISICLII MUG Vi VIC %Amid uasin, usc Maria are poor in quality, but they yield some-
what more information than would simple bathy-
metric recordings. Geomagnetic records from all
three ships plus four traverses from Project
MAGNET total about 26,500 line-km.
Flo. 2?Diagrammatic map of China basin and vicinity. Wide lines frame area portrayed in subsequent charts.
From Heezen and Tharp (l971).
bottom topography of the Manila Trench and the
West Luzon Trough drawn by Irving (1951) and
Dietz (1954) was updated by Ludwig et al. (1967)
and by Chase and Menard (1969). Seismic pro-
files, made chiefly by geophysical ships of the
Lamont-Doherty Geological Observatory arriv-
ing and departing Manila, used mainly half.
pound charges of TNT as the sound source. The
profiles of Ludwig et al. showed sediments about
1.5 km thick in the West Luzon Trough, of vari-
able thickness in the Manila Trench, and 0-1.5
km thick on the floor of the eastern China basin
where the nearly horizontal layers tended to
smooth an irregular bottom that was identified as
oceanic basement (or Layer 2). Hayes and Lud-
wig (1967) found that the trench and trough have
negative free-air gravity anomalies, and magnetic
anomalies that could not be traced over apprecia-
ble distances. Seismic velocity, measured at 13
refraction stations in the eastern China basin by
Ludwig (1970), yielded 2.1-2.6 km/sec for sedi-
ments, and 4.4 km/sec for basement. Earth-
quakes are rare in the China basin except near
the Philippine Islands (Gutenberg and Richter,
1949, p. 58-61; Hayes, and Ludwig, 1967) and
east of Taiwan (Katsumata and Sykes, 1969).
Most are shallow (less than 100 km) and exhibit
little relation to known faults (Allen, 1962), but
they do occur along a westward-dipping focal
plane.
Between June 3 and August 26, 1969, a general
geophysical study of the South China Sea (north-
ern Sunda Shelf and southern China basin) was
made aboard R/V F. V. Hunt on contract to the
U. S. Navy Oceanographic Office from the Ma-
rine Acoustical Services of Miami, Florida.
Transit to and from Chilung, Taiwan, plus tra-
verses previously reported by Parke et al. (1971)
in the southern end of the China basin, total
about 8,900 line-km. All these traverses included
seismic profiles using a 30,000-joule sparker with
analog recording, and magnetic measurements
using a proton-precession detector. Unknown to
us at that time, additional seismic profiles with a
20,000-joule sparker, plus magnetometer mea-
surements, had been made between September
15, 1967, and February 27, 1968, aboard Ruth
Ann and Santa Maria, two ships of Alpine Geo-
physical Corporation of Norwood, New Jersey,
on contract to the U.S. Navy Oceanographic
Office (May et al., 1969). About 9,400 km of fair
to good seismic profile's are from -traverses_of-
Ruth Ann which, combined with the seismic pro-
files of Hunt, total 18,300 line-km. An additional
10,100 km of seismic profiles mainly from Santa
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TOPOGRAPHY
Bathymetric contours of the China basin and
vicinity (Fig. 3) were taken from the compilation
by Chase and Menard (1969) through interpola-
tion at 1-km depth intervals from their 200-fm
contours. The chart also includes the 150-m con-
tour to show the approximate position of the
shelf-break. The widely spaced contours of Fig-
ure 3 fail to reveal many of the topographic de-
tails of Figure 2, but the two figures supplement
each other. In contrast to the flat shelves, most
side slopes of the China basin are very irregular
owing to the presence of fault blocks, volcanoes,
and calcareous reef structures. Fault blocks or
slumps also are present low on the slope border-
ing the northwestern (mainland China) side of
the basin, where they interrupt the surface of A ? '-
basin rise. Smooth side slopes are present only at
the southwestern end of the China basin, where
Parke et al. (1971) showed the presence of sedi-
ment prograding northeastward from the adja-
cent northern Sunda Shelf.
On the floor of the basin are broad hilly,
areas?fault blocks, volcanoes, and calcareous
reefs. The hilly area on the southwest includes
Reed Bank and many smaller banks .and reefs,
many of which have been named for ships
wrecked upon them?giving rise to the general
name for this region as the Dangerous Ground.
Another large area of hilly basin floor borders the
western and northwestern side of the basin; it
includes Macclesfield Bank, the Paracel Islands,
and many smaller reefs. The Paracel Islands have
a small village with a tower and meteorological
station. This group and the other islets containing
only temporary habitations and inadequate navi-
gational aids are poorly mapped (U. S. Naval
Oceanog. Office, 1967, p. 71-88) and have uncer-
tain sovereignty.
The smooth prograded side slopes on the
southwestern and to a lesser extent on the north-
eastern end of the China basin continue basin-
ward as gently sloping aprons or basin rises that
gradually flatten into abyssal plains. The largest
abyssal plain occupies the central area of the
basin, where the bottom is exceedingly flat at
about 4,350 m. A much smaller abyssal plain ?
floors the Palawan Trough near Borneo at about
2,850 m. Additional bottom contours that show
the prograded sediments, their lower slopes, and
their abyssal plains have been included ,on the
842 K. 0. Emery and Zvi Ben-Avraham
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Structure and Stratigraphy of China Basin 843
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geologic map of the China basin (Fig. 15) as oceanic basement, or Layer 2. Locally, volcanic
interpreted from available seismic profiles, peaks, massive coral reefs, and older folded sedi-
? Sediments at the eastern side of the China ments have similar reflective properties and must
basin slope downward from the nearly flat basin be included with acoustic basement. In the south-
floor into the steep-sided Manila Trench; the ern part of the China basin basement was pene-
southeastern end of the trench also has a smooth planed before being buried under sediments and
slope toward the 5,000-m deepest point just west then folded (Parke et al., 1971, Figs. 21-23); this
of Luzon. East of the trench, the West Luzon may be a northward continuation of pre-C,eno-
Trough has a flat floor at about 2,600 m that may zoic igneous and metamorphic rocks beneath the
be blocked off from the deeper (about 3,200-m) Sunda Shelf. Acoustic basement generally is bur-
floor of the northern extension of the steep-sided ied beneath sediments, but locally it protrudes
trough which has been termed the "North Luzon upward as isolated peaks or areas having very.
, ? -
Trough" (Ludwig, 1970). irregular topography.
The entire area of Figure 3 is 2.7 million sq km, Above the acoustic basement is a sedimentary
blanket that follows many of the undulations of
and the area of the China basin beyond the shelf-
the basement. Elsewhere, it is folded and faulted,
break is 1.8 million sq km?nearly one quarter
the area of the conterminous United States.
and abuts the steeper slopes of basement topog-
raphy. The most intense folding? is associated --"
GEOMAGNETICS ' with basement projections and it forms a series of
Magnetometer data from R/V F. V. Hunt, ridges that trend northeast-southwest. These ?
Ruth Ann, Santa Maria, and airplane line Project ridges are crossed by the profiles of Figures 6-8;
and are paralleled by those of Figures 9-11.
MAGNET were digitized, and the regional gra-
Where the unit crops out, the topography is:--,-4?
dient Was' removed by a computer program at
Woods Hole Oceanographic Institution. The re-
. gently rolling and smoother than that for out-
crops of acoustic basement (Fig. 12). Following
suiting lines of magnetic anomalies were plotted
the usage of Parke et al. (1971), the sequence is
along the various traverses (Fig. 4). Anomalies in
termed "predeformational sediment." This is
the southern, western, and northeastern parts of somewhat simplified terminology, because at
the basin are subdued, presumably because of the least two periods of deformation can be clis-
great depth that magnetic basement has been cerned locally through the presence of uncon-..
buried beneath sediments. Anomalies west of Lu- formities, but they cannot be traced for more
zon are larger, probably reflecting the presence of than a few kilometers or correlated from place to
volcanic mountains that rise high above their
surroundings. The degree of correspondence of The third and shallowest consistent sequence
magnetic anomalies with topography and struc- occupies the troughs beneath the continental'
ture is best shown on the geophysical profiles of shelves (Fig. 13) and the areas of lowest topogra--:
Figures 6-11. phy within the China basin. Quite clearly, it is a
sedimentary fill dating from the cessation of most
diastrophic activity. This fill is termed the "post-
deformational sediment," again in accordance
with the terminology used in Parke et al. (1971),
and in spite of the fact that in several profiles
across this unit, some slight deformation is evi-
dent, caused by slumping or underthrusting along
the Manila Trench (Fig. 14). The postdeforma- -
tional sediments contain many good internal re-..
flectors that are interpreted as sandy turbidites.
In contrast, continuous discrete reflectors are less
numerous in the pre-deformational sediment,
which locally may even be acoustically transpar-
ent. The interpretation of the post-deformational
sediment as being largely turbidite in origin ac- ?
The records revealed three main kinds of cords with its distribution as a progradation from
acoustic units,as already discussed-by Parke-"irr,:^4Y,the---contipental.. shelves down the basin side
al. (1971) for the southern part of the basin. slopes. Where sediment sources appear to be
Deepest is acoustic basement, the deepest reflec- great, the post-deformational unit continues
tor for the available energy, and the one that is smoothly down the slopes in the form of narrow.
believed to consist largely of igneous rock?the aprons whose slopes gradually merge into flat -
2012/09/12 : CIA-RDPO8C01297R000200130010-7 .
C NINA
0 Paracel
Islands
Macclesfield
Bank
1
i3 0 R N E a.
Flo. 3?Topography of China basin and adjacent shelves. CI = 1 km, with 150-rn contour added as dashed line.
Interpolated and redrawn from Chase and Menard (1969).
.11
Declassified and Approved For Release
SEISMIC PROFILES - .
The paper recordings of the continuous seismic
profiles had been microfilmed and only flow-
camera prints of the films were available to
On these prints we marked in colored pencil the
various kinds of reflecting surfaces. Only previous
experience with the high-quality records from
Hunt permitted identifications on many of the
seismic records from Ruth Ann because of the
generally lower power, poor microfilms, and
short discontinuous traverses of the latter (Fig.
5). However, the final product from all three
ships provides good coverage of the entire China
basin in the form of structural sections.
115'
I
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120'
For Release
. , Structure and Stratigraphy of China Basin
2012/09/12 : CIA-RDPO8001297R000200130010-7
abyssal plains in the deepest parts of the basins
(Fig. 15). Detailed examination of bathymetric
profiles by J. Mammerickx of Scripps Institution
of Oceanography (personal commun.) revealed
the longest apron to be cut by deep-sea channel
with natural levees, particularly near lat. 12?N.,
long. 113?E. ?
The geologic map of Figure 15 also denotes the
parts of seismic profiles that indicate outcrops of
acoustic basement. Because these outcrops are
small and discontinuous no attempt was made to
group them. However, most of them are within
the areas of predeformational sediment.
A generalized impression of the distribution
pattern of the three stratigraphic units and their
relation to the topography. is given by the three-
dimensional model of Figure 16. This model is
viewed from the south, and it contains parts of
profiles 9-9', 10-10',.11-11', 12-12', H-H', J-J',
and L-L'. Careful inspection reveals several
ridges composed of pre-deformational sediment
. and acoustic basement trending northeast, and
separated by low, flat-bottomed areas' underlain
-
by post-deformational sediment
-
Discussiort
Geologic ,Dates.
The major events recorded in the stratigraphy
and structure of the China basin appear to be the
peneplanation of acoustic basement and the fold-
ing that separates the predeformational and the
postdeformational 'sediments.
The basement rocks of the Indochina Penin-
sula, the Malay Peninsula, Sumatra, and Borneo
continue beneath the shallow Sunda Sea, and
they consist mainly of Paleoioie and Mesozoic
metamorphic and igneous rocks.,A review of evi-
dence for the Late Cretaceous age of the pene-
plain on acoustic basement south of the China
basin is provided by Parke et al. (1971) and Todd
and Pulunggono (1971). Magnetic (Bosum et at,
1970) and gravity (Pan, 1967; Hsieh and Hu,
1971) surveys and drillhole samples from the
Penghu Islands west of Taiwan (Huang, 1967;
_Chou, 1969) indicate that Mesozoic strata are far
denser than Cenozoic ones, in agreement with the
concept that the top of acoustic basement there
could be the Late Cretaceous peneplain. In the
Philippines a major unconformity also separates
the Cretaceous and Tertiary Systems (Gervasio,
1966, 1968). No more specific evidence for the
age of?the acoustic basement k9ck-ot4zit.s.:.arie-
plain is known from the China basin.
The large Northwest Borneo geosyncline con-
tains thick, highly folded and faulted Paleogene
4?Lines of magnetic anomalies from ship and airplane measurements across China basi ?
Four airplane lines (Project MAGNET) " " ' . ? sediments. Only sediments younger than middle
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845
Miocene have gentle dips. In this region the Pa-
leogene sediments appear to have been deposited
in deep water, and the late Neogene ones in
shallow water, presumably the reverse of the.
depth sequence in the China basin (Parke et a/.,.
1971). In Taiwan, the Cenozoic sediments older
than Pliocene are folded and faulted, and they . ?
form much of the Central Range (Juan and
Wang, 1971). Lapping against them are thick
"muddy sediments" of late Pleistocene age. The
Miocene sediments are largely bedded sand-
stones with ripple marks; and the Pleistocene
"muddy sediments". are massive mudstones, pos-
sibly of deep-water origin. In the Philippine Is-
lands, as on Taivfan, there was a major tectonic
episode during -late Miocene time, followed by
postorogenic sedimentation interrupted by vol-
canism and other tectonic activity (Gervasio,
1968). Uplifts and subsidence during the entire'
Cenozoic are well documented on the islands of
Palawan, Mindoro; and Luzon; these movements.
resulted in cycles of arkosic marine sediments'.
alternating with limestones. Folding and upliff1-
have continued to the present 'along the' eastern' -
edge of the China basin, as indicated by raised'
Holocene calcareous reefs near the south end of
Taiwan (Hashimoto et al., 1970), by a 25-km left-
lateral movement of the East Taiwan rift since
late Pleistocene time (Biq, 1967), by the 1,200-km
long left-lateral movement of the Philippine fault
(Allen, 1962), and by the folding of "post-defor-
mational" sediment in the Manila Trench (Fig.
Until drill data are available from the floor of
the China basin, we believe that the best age -?
estimate for the unconformity at the top ,of the ?
acoustic basement is Late Cretaceous. The main ,
time of subsequent folding is.probably early Neo-
gene, with activity continuing to the present:.
along the eastern side of the China basin. ? -
Structural Implicatiohs . ,
.
The distribution of the ridges beneath the outer'
edges of the continental shelves and across the
floor of the China basin (Figs. 6-11, 16) is pre-
sented in simplified form in Figure 17. Ridges 7: ,
surround the basin, where they served as sub-' -
merged dams to trap large quantities of detrital ,
sediments brought to the ocean by rivers. One Of
the ridges bordering the shelf off Borneo contin-
ues northeastward as the elongate Palawan Is- ?
land. These barriers appear to be close parallels
with the ones previously observed in the East ?
China Sea and the South China Sea. The ridge at
the edge of the continental shelf off mainland.
China is known from only a few traverses, best of
which is one by United Geophysical Corporation
across the outer part of the shelf directly south-
east of Hong Kong (Figs. 5, 13). In this area the-
?
20'
110?
C H I
K. U. Emery and Zvi Ben-Avraham
Structure and Stratiaraphy of China Basin
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ic120'
TAiWAN
15'
10'
?
/I ,- ?
----- '
%-
OR N E
Flo. 5?Positions of best seismic profiles?from R/V F. V. Hunt (wide lines) and Ruth Ann (narrow lines). Dotted line across
outer shelf at lat. 21?N, long. 115?E, is from United Geophysical Corporation (Fig. 13). Interpretive drawings are shown on Figures
6-11.
? . o
22? 30' N.
116? 55',E.
+500-
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0 -poo-
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20* 05' N.
124- oe E.
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19? 47'N.
115* 50'E. ?
19? 02' N.
117? 22' E.
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20? 40'N.
117? 53's.
847
19? 53' N.
121? 00' E.
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120* 10'E. 116' 25'E.
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118* 35' E.
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419? 53' E.
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6?Interpretative seismic and magnetic.profiles along traverses 2-2', 3-3', 4-4', 5-5', and 6-6' (Fig. 5), assuming
acoustic velocity of 1.5 km/sec in water and-/.0-tiri/sec in sediments. Top: Total intensity magnetic anomalies. Bottom: Line-
drawing interpretation of continuous seismic reflection profiles, vertical exaggeration 26.7x. Black indicates acoustic basement;
coarse dots, predeformation sediments; and fine dots, postdeformation sediments. Small horizontal bar and p designate part of
recording illustrated by photograph.
? . -
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848
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Structure and Stratigraphy of China Basin
110 00 N. ?
109? 23' E.
(I) +5007
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Cl) +500
2 0
2
0 -500
3.0
2 ,5
c
4--
7? 26' N.
109? 00' E.
5? 00' N.
111? 10' E.
Ii
+500
Flo.. 8?Traverses for 10-10', 11-11',12-12', and 13-13'. Symbols.are same as for Figure 6.
0
-500
O 12'
2
4
+500
0
-500
O 13'
2
4
Declassified and Approved For Release 2012/09/12 : CIA-RDP08001297R000200130010-7
Declassified and Approved For Release 2012/09/12 : CIA-RDP08001297R000200130010-7
850 K. 0. Emery and Zvi Ben-Avraham
1 2'
10'N.
13? 35'N.
109'
41' E.
111? 06E.
+500
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Ao
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2 2
4
18?
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2040'N.
117?
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117? 101E.
4
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109? 50' E.
+500 +500
0 0
7500 -500
Bo 131 Co
4
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Fo
4
17? 35' N. 18? 08'N.
111?49' E.
:
., 2.-.,1>,A
21? 50'N.
117* 42'E.
31'E.114
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21?01'N.
119* 21'E.
+500 +500
0
21? 05'N.
118? 19'E.
-500
Go
0?
0 100 200 KM
2
4
Flo. 9?Traverses A-A', B-B',.C-C', D-D', E-E', 12-F', and 0-0'. Symbols are same as for Figure 6.
1
0
-500
0 GI
2
4
0
0
in 0&
00
SVAINV
Declassified and Approved For Release 2012/09/12 : CIA-RDP08001297R000200130010-7
500
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0
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N.
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-500
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0
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Declassified and Approved For Release 2012/09/12 : CIA-RDP08001297R000200130010-7
00
0
/
Structure and Stratigraphy of China Basin 851
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Flo. 10?Traverses 1-I', K-K', and M-M'. Symbols are same as for Figure 6.
Declassified and Approved For Release 2012/09/12 : CIA-RDP08001297R000200130010-7
Declassified and Approved For Release 2012/09/12 : CIA-RDP08001297R000200130010-7
852 K. 0. Emery and Zvi Ben-Avraham
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o o
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? Luzon Trough (pr
13?Sc?
ridge beneath ou
Corporation and
Declassified and Approved For Release 2012/09/12 : CIA-RDP08001297R000200130010-7
Declassified and Approved For Release 2012/09/12 : CIA-RDP08001297R000200130010-7
Structure and Stratigraphy of China Bain
853
DISTANCE IN KM
Fin. I2?Section of seismic recording and of its interpretation showing repeated wes
Luzon Trough (profile 6-6' of Figure 6 at lat. 14?25', long. 119?35') caused by repeated uplift
ward thinning of sediments in West
f bordering ridge.
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