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The Permian of Vietnam, Laos and Cambodia and its interregional correlation
Persian-Triassic Evolutionof Tethys and WesternCircum-Pacific H. Yin, J.M. Dickins, G.R. Shi and J. Tong(Editors) o 2000 ElsevierScienceB.V. All rightsreserved.
The Permian correlation
of Vietnam, Laos and Cambodia
99
and its interregional
Cu Tien PHAN Research Institute of Geology and Mineral Resources, Thanhxuan, Hanoi, Vietnam
The newly obtained research results allow correlation of the Permian of Indochina with those of China and other regions although with varying confidence. The clearest boundary in the local Permian stratigraphic scheme has been assigned to the base of the Dzhulfian formations. Some new data allow determination of a boundary at the base of the Permian and possibly the Upper Carboniferous - Permian. In Indochina, the fusulinids are of special significance because of their common occurrence and rapid evolution; however the contribution of data from other groups of organisms is and will remain of great significance. Lower and Upper Permian could be retained as series of the Permian according to their general usage and subseries can be recognized in the Upper Permian of Indochina Peninsula and adjacent territories of Southeast Asia and Eastern Asia.
1. I N T R O D U C T I O N This paper will not deal with the whole Indochina Peninsula. It is concerned mainly with Cambodia, Laos and Vietnam, the Indochina countries; however the Permian formation of the three countries will be correlated with those of Thailand, Malaysia of Indochina Peninsula and South China, Japan as well. The first description of the Permian formation of Indochina were presented in the beginning of this century. These are Productus Quartz Sandstone, Fusulinid-bearing Limestone and others [1, 2, 3]. Relating to the tectonostratigraphic interpretation, Fromaget considered the Permian formations of Indochina as parts of Anthracolite Limestone or Indosinias Terrigene [4]. In the view of stratigraphic correlations. Saurin classified the Permian formations into Artinskian, Kungurian, Kazanian, or some fusulinid horizons [5, 6]. Since 1954, in the geological publications, the Permian formations of Vietnam and its relationship with the Carboniferous were described as a monotonous sequence belonging to the "tectonic leveling" of the territories [7]. However on the basis of newly collected data, Permian formations of Vietnam in particular and Indochina Peninsula in general were recognized to be complicated with various composition and abundant mineral resources[8-10]. In the geological development of Vietnam and adjacent territories, the Permian geological events accompanying the change of structural framework, palaeogeography and volcanic
100 activities have been identified.
2. P E R M I A N
VOLCANO
- SEDIMENTARY
FORMATIONS
In Indochina, the following stratigraphic regions have been classified in the geological map of Cambodia, Laos and Vietnam: Vietbac, West Bacbo, Truongson, Kontum Savannakhet, Dalat Stungtreng and Northwest Laos [9]. These regions are separated from the West Thailand region by the Nan Suture (Fig. 1). In the Vietbac, the lower part of Permian is characterized by monotonous, black, grey limestone corresponding to the upper part of the Bacson Formation of Carboniferous Permian. The definition of Permian is mainly based on Schwagerina or Robustoschwagerina, Misellina, Cancellina, Neoschwagerina, Lepidolina - Yabeina horizons of Asselian - Midian [11-15]. Here, the Dongdang Formation of D z h u l f i a n - Darashamian age overlies unconformably on the eroded surface of the above mentioned limestones and comprised basal bauxite beds, shale, chert and limestone. The limestones contain Codonofusiella aff. paradoxa Dunbar et Skinner, Dunbarella sp. in the lower part and Palaeofusulina prisca Deprat, Colaniella parva (Col.), Reichelina pulchra M. Maclay, Neoendothyra eostaffelloidea Liem and Leptodus sp., in the upper part. The Lower Triassic sandstone, silstone containing Claraia, Glyptophiceras overlies the above - mentioned formation with an either conformity or a disconformity [16]. In some places such as Baichay, the Upper Permian comprise quartzite, shale, chert and coal seams. The collected fossils are Meekella cf. ufensis Tchernyshev, Lyttonia sp., Productus gratiosus Waagen, Martiniopsis aff. orientalis Tchernyshev, Spiriferina cambodgiensis Mansuy, Pseudomonotis cf. garforthensis King, Pseudophillipsia cf. acumulata Mansuy,... [1 ]. In the West Bacbo region, the Permian sedimentary sequence is presented mainly by the Lower Permian and may be Upper Carboniferous as well (Table 1). In the southwestern periphery of the region, at Thanhhoa area, the Lower Permian limestone continuous from the Upper Carboniferous limestone; however the Upper Permian mafic volcanics of the Camthuy Formation overlies unconformably the older formations. The formation is composed of volcanics belonging to the picrite - basalt association, 700 - 800m thick. Overlying the mafic volcanics, there are shale, chert, coal shale, coal seams, limonite, hematite beds in places and limestone of the Yenduyet Formation. The thickness of the coal seam varies, from 20 - 30 cm to 6 m. Limonite, hematite beds have the thickness of 3 m, Fe203 varies from 23 - 37% to 62% in places, A1203 22 - 23%, SiO 2 12-17%. The collected fossils in shales comprises Leptodus sp. (cf. L. nobilis Waagen), Squamularia sp., Schellwienella sp., Chonetes sp., Actinodesma sp., Spiriferella sp., Neophricodothyris cf. asiatica Chao and Aviculopecten sp., Oldhamina sp., Marginifera cf. lopingensis (Kayser), Andersonoceras sp., Pseudotirolites sp., Gigantopteris sp., Pterophyllum sp. [18] and Chonitipustula sp., Dielasma sp., Productus (Alexenia ?) sp., Chonetes sp., Spirifer sp., [7]. Similar sections also crop out in Sonla, Laichau along the eastern periphery of the Songma anticlinorium, the collected fossils comprise Peltichia kwangtungensis (Zhan), Acosarina minuta (Abich), Rhipidomella hessensis King, Schuchertella cf. cooperi Grant, Derbyia sp., Waagenites soochowensis (Chao), Spinomarginifera chenyaoyanensis Huang, Marginifera gen. et sp. indet. [17]. The relationship between the Upper Permian and Lower Triassic is conformity or disconformity.
101
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225 I
300 Ikm
Figure 1. Stratigraphic Regions of Cambodia, Laos, Vietnam (main land) and adjacent regions. VIETBAC
Stratigraphic region name
/
i
Deep - seated fault
102 In the Da river valley, mafic volcanics have great thickness, various composition and are closely related to ultramafic and mafic intrusions. It seams possible to define 3 magmatic associations from the lower part to the upper part of the section. These are picrite basalt andesite association closely related to the picrite diabase association; basalt komatiite and trachydacite, trachyandesite basalt association. The above association underlie siltstone, shale, marl, sandstone of the Lower Triassic (Olenekian). In the picrite basalt of the picrite basalt andesite association, the percentage of basalt reaches 70 - 80%. According to the petrochemical characteristics, these rocks are rather highly alkaline and high in TiO2. Total alkaline reaches 3% in subultramafic and 3.6% in mafic intrusion; TiO2:1.8 and 2.2 respectively; K20/Na20: 0.38; A1203:8.4 - 24 and FeO: 8.4 -
14%.
Pertaining to the picrite diabase association, there exist dike, veins and subvolcanic bodies of peridotite, picrite diabase and gabbro ophyte belonging to the ultramafic, ultramafic - mafic and mafic groups. The ultramafic group is characterized by low alkalinity. Na20 + K20 < 1%; TiO2 < 1; A1203:5.17 - 5.56; relatively high MgO: 3.0 - 4.5%; Na is predominant. Basalt komatiite association is recently defined in the center of Da river valley and composed of komatiitic peridotite (20 - 40% MgO), komatiitic basalt (12 - 20% MgO), olivine bearing basalt rich MgO and leucocratic basalt (< 8% MgO). Petrochemically, the association is characterized by TiO2:0.12 - 0.19; CaO/A1203:0.8 - 1.1; CaO/TiO2:14.4 - 21.5 and A1202/TiO2:18.3 - 23.4%. The trachydacite-trachyandesite-basaltoid association crops out mainly in the eastern periphery of the region and seems to be of Permian and Permian-Triassic age. This association is characterized by high alkaline, alkaline and subalkaline rocks, SiO2:49.4 - 67.5; TiO2:0.7 - 3.7; A1203: 14; MgO: 0.4 - 6.3; CaO: 1.1 - 8.3%; total alkaline > 4%, among them K > Na in trachyandesite. The contacts between the volcanic formations and other ones are mainly tectonic. The intercalation of sedimentary and volcanic rocks can be seen in some places such as the Hoabinh hydroelectric dam site. In ascending order this section comprises of: 1) basaltic porphyrit, 20 m thick; 2) limestone, marl, 20 m thick; 3) carbonate siltstone containing badly preserved brachiopods, 10 m thick; 4) limestone containing Triticites (?) sp., Pseudofusulina sp., Misellina ovalis Deprat, 20 m thick; 5) basalt, tuffs, 17m thick; 6) sandstone, siltstone, marl containing Ditomopyge sp., Aulacorhyncus protechwensis Grabau et Tien,
Propinacoceras aff. aktubense Rhyzhensev .... 15m thick; 7) limestone containing Misellina ovalis (Deprat), Neofusulina sp., Pseudofusulina sp., 30 m thick [8]. In the Truongson region, Permian and Carboniferous limestones crop out in continuous sections at Quydat, Muongxen of Vietnam and Nonghet, Khammoun, Vangvieng of Laos. Permian limestone contain abundant fusulinids corresponding to the Schwagerina, Robustoschwagerina, Misellina, Cancellina and Neoschwagerina horizons. Uppermost part of the Permian have been observed in places. At Khegiua area, limestones contain Codonofusulina nana Erk, Neoendothyra eostaffelloidea Liem, Palaeofusulina (?) sp., Reicheline (?) sp. [13], and at Camlo area, shales contain Leptodus nobilis (Waagen), Chonetes subtrophomenoides Huang and Meekella kweichowensis Huang [18]. The relationship between the above limestones and older formations is not defined yet. The Permian volcano sedimentary formation of this region is restricted to the narrow band along the fault in Alin area of Vietnam and enlarged in Khangkhay area of Laos. Along the
103 road N017 from Phonsavan to Khangkhay, the formation is composed of grey shale, marl containing Plicatifera sp., Schuchertella sp., Anarsalites sp. of the lower part; red coloured carbonate, siltstones, sandstones of upper part [9]. In the Dalat Stungtreng region, the Daklin Formation of the Upper Carboniferous-Permian crops out in the same name in Vietnam and comprises shale, chert, andesite, basaltic andesite in the lower part; andesite, tufts, sandstone in the middle part; and andesite, basaltic andesite, dacite, rhyolite, marl, limestone in the upper part. The collected fossils are badly preserved bryozoans, crinoids, brachiopods in shale and Sschwagerina sp., Pseudofusulina sp., Verbeekina sp. in the limestone. The volcano-terrigenous formations distributed in the Stungtreng, Preah Vihear, Siemreap of Cambodia can be correlated with those in the Daklin area. The intercalations of volcanic rocks and limestone were observed in the right band of Mekong River, North of Stungtreng, in Chhep and Stungtreng [19, 20]. Permian limestones crop out in Hatien of Vietnam, Campot, Phnomxa and Battambang of Cambodia. The Hatien Formation in Vietnam is characterized by limestones containing Verbeekina verbeeki Genitz, Neoschwagerina margaritae Deprat, Codonofusiella sp., Parafusulina sp., Nankinella sp. and gastropods, rugose corals and crinoids [9, 16]. In Phnomxa of Cambonia, the Permian formation is composed of: 1) basal conglomerate containing fragments of quartzite, sandstone, rhyolite; 2) oolitic limestone; 3) fossiliferous marl, limestone; 4) siliceous limestone containing sponge and radiolarians; 5) massive limestone [ 19]. According to Dottin and Langle [20], the Permian stratigraphic scheme of Cambodia is composed of: 1) limestone containing Yangchienia and Cancellina of Artinskian age; 2) limestone containing Praesumatrina dunbari in Phnom Svai and Verbeekina verbeeki, Neoschwagerina douvillei in Battambang of Kungurian age; 3) limestone containing Yabeina and Lepidolina of Kazanian age; 4) limestone containing Brachiopoda in Battambang of Upper Kazanian and 5) limestones schists in Svaycheck of Tartarian age. The uppermost part of Permian crops out in Tathiet, at the Cambodia-Vietnam border and comprises siltstone, sandstone, shale containing Streptorhyncus cf. perlargonatus (Schlotheim), Uncinunellina sp. (aff. U. timorensis Beyrich), Giriypecten sp., Palaeolima sp. in the lower part and limestone containing Palaeofusulina prisca (Deprat), Colaniella parva (Col.), Reichelina pulchra M. Maclay, Neoendothyra dondangensis Liem in the upper part. The above-mentioned sediments conformably underlie sandstone, siltstone containing Claraia, Otoceras (Motococeras) of the Triassic [ 16, 21 ]. Except the carbonate terrigenous formations, andesite, rhyolite, tufts, aglomerate in Honchong of Vietnam and in Campot of Cambodia were classified into Permian-Triassic in the correlation with those in West Thailand and Malaysia [22, 23]. In the Northwest Laos region, the Songda Formation at the Muongte area of Vietnam is made of coglomerate, sandstone, shale, chert, andesite, rhyolite and limestone containing Pseudofusulina sp., Parafusulina ex gr. japonica (Gumb.), Misellina ex gr. ovalis (Deprat) and Chonetes sp. [7, 9]. In the territory of Laos, the Permian formations comprise also sandstone, shale, tufts and limestone containing Orthoceras sp., Griffitides sp., Productus aagardi at Sayabuli and Pseudofusulina japonica, P. gigantea at Nambac valley [5]. In this region, Fromaget [4] described a coal-bearing formation of Permian age at Soppong. Here, sandstone, shale and coal-shale contain Gigantopteris nicotinaefolia, Cordaites cf. Principalis and Schizoneura gondwanensis. The relationship between the Permian volcanosedimentary, carbonate and coal-bearing formations has not been defined yet.
Table 1 9 Permian Stratigraphic Correlation of C a m b o d i a , Laos and V i e t n a m Dalat
- Stungtreng
Truongson
West Bacbo |
Hatien, Battambang
Tathiet
West Hue, Xiengkhoang
Daklin, Stungtreng
Quydat, Nonghet
Lower Triassic:
Lower Triassic i
Sonla, Thanhhoa
Vietbac Vanyen, Hoabinh Lower Triassic 9
Otoceras
Claraia and
Costatoria and
Clarata, Lingula
(Metotoceras) and
Lytophiceras ....
Eumorphotis ....
and Glyptophiceras ....
....................... Yenduvet Formation
Lobatannularia,
Dongdang Formation
Palaeofusulina and
Pecopteris,
Palaeofusulina and
CodonofusieUa Horizons
Gigantopteris ....
Codonofusiella
Leptodus Chonetes and Gigantopteris, ...
Volcanics
Claraia .... i 9- - - . - - ~ - P e r m i a n - Triassic i Volcanics
...................
Permian - Triassic
Camlo s h a l e s
Volcanics
Leptodus, Chonetes
9
and Dyctyoclostus .... .....................
Tathiet Formation
..................
Palaeofusulina Horizon
Viennam Formation
Horizons Leptodus
Volcanics
Upper pa~ of
!
Hatien (Battambang)
A l i n (Khangldaay)
Formation:
Lepidolina and
Daklin Formation
Neoschwagerina
Verbeekina
Horizons
Pseudofusulina and Schwagerina (?) .... Volcanics
Muonglong
Upper part of
(Nonghet) Damai Formation :
Bandiet Formation
Bacson Formation :
Formation 9
Formation:
Neoschwagerina,
MiseIlina, and
Neoschwagerina,
Plicatifera, Anatsalites
Neoschwagerina,
Misellina,
Robustoschwagerina
Misellina,
and Schuchertella ....
Cancellina, Misellina, Robustoschwagerina and
Horizons
Robustoschwagerina
Volcanics
Robustoschwagerina and
Propinacoceras
and Schwagerina Horizons
Schwagerina Horizons
Schwagerina Horizons
Schwagerina ,,--"""
?
Upper part of
Neoschwagerina,
"rtticttes Horizon
...'"""" Horizons
Titicites Horizon
Triticites Horizon
105 3. S T R A T I G R A P H I C C O R R E L A T I O N OF PERMIAN FORMATIONS. The newly obtained data in Cambodia, Laos and Vietnam allow a correlation of Permian formations of the three countries with those of South China and adjacent regions although with different confidence. In the Vietbac region, the boundary between the Neoschwagerina-bearing limestones of the Bacson Formation can be correlated with the base of the Wuchiaping Formation of the Lopingian Series or the top of the Maokou Formation of the Yangsingian Series [24]. The latter have been correlated with the Guadalupian Series [25]. In the West Bacbo, the mafic volcanics of the Camthuy Formation is easily correlated with the Omeishan Basalt Formation in Yunnan and Guizhou of China although their origins may be complicated. The Yenduyet Formation may correspond to two formations of Lopingian Series and the volcanics of Bandiet Formation are also correlatable with those of the Maokou Formation in the above-mentioned provinces of China (Table 2). For long, in China the lower boundary of the Permian has been placed at the base of Chihsia Formation containing Misellina claudiae which was originally defined in the Nanjing area where the formation lies with a hiatus on older beds [24]. This practice has also been followed in Vietnam [ 14, 15]. More recently practice has tended to look for a Lower Permian basal boundary equivalent to the base of the Asselian as used in the Ural area and many other parts of the world. The traditional subdivision is thus rather in a state of flux. As discussed below a return to the orginal definition of the Chihsia has a potential for a clearer correlation with Japan and the two subdivisions of the Upper Permian (for a twofold Permian System), the Yanghsingian and Lopingian [ 10]. The geological events at the top of the Bacson Formation in the Northeast and West Bacbo of Vietnam or the Maokou Formation in the Yunnan and Guizhou of China seem to be unclear in the Truongson and Dalat Stungtreng regions. Fromaget [4] recognized the Moscovian geological event in Indochina. However it is unconfirmed by recent investigations. Some newly obtained data in Vietnam and in Laos allow determination of boundary at the base of the Khangkhay, Daklin and possibly Hatien Formation. May be, this boundary coincided with the boundary in Upper Carboniferous-Permian in the regional column of Khorat Plateau [26, 27]. The Tathiet Formation at the uppermost part of the Saigon river can also be correlated with the limestones in the Doi Pha Pleung, Amphoe Ngao and Changwat Lampang areas and in some other places [28]. The Permian - Triassic Honchong Formation may also be equated with the volcanic sequences of the same age in Thailand and Malaysia [20, 22]. Considerable progress has recently been made in Central and Western Thailand. In Central Thailand, strong folding and orogenic activity with flysh formation has been described in the Kubergandian- Midian [29]. In Western Thailand, an unconformity seems to present at the base of the Permian or Upper Carboniferous sequences. However the detailed descriptions and age remain unclear [30, 31]. In most recent publications [32, 33], a local subdivision of the Permian has been used, in which the Lower Permian remains poorly known, the rest being composed of Kubergandian and Murgabian belonging to Middle Permian and the Midian together with the Dzhulfian and presumably the Dorashamian and equivalents belonging to Upper Permian. Whether the Midian-Dzhulfian event is present in Thailand as found in Vietnam, China and Japan is thus unclear. The Middle Permian, however, is apparently represented in the beginning of the orogenic event in the Kubergandian, and Dawson [32, 33]
Table 2 9 Stratigraphie Correlation of Permian in Vietnam and Adjacent Regions Traditional standard Southern
Proposed classifi cation of SPS
Urals
Changhsinglan
Armenia Iran, Pamir
South China Changhsingian Palaeofusuhna smensls P. minima Gallowaynella meitwnsis Wuchiapin~oian Nankinella simplex Codonofuswlla kwangstensts
Darashamian
-~o Wuchiapingmn
Dzhulfian
South Kitakami, Japan
Nabekoshian Palaeofusulina sp.
~o G
Maehaman
Lepidolina kumaensis Lepidohna kumaensts
i
Palae@r Gallowaynella Colaniella Codonofuslella E
Capitanian
Wordian
Kazanian
Ufimian
Roadian
Kungurian
Kungurian
.~
Artinskian
Murgabian
Kubergandianian
Blorian
Yakhtanshian
Sakmarian
Sakmarian
Sakmarian
Asselian
Asselian
Asselian
[251
Jin et al (1997)
[251
Kotlyar, 1987 Leven et al, 1993 in Jin et al., (1994)
[241
=
~:~ >-
y.
Lengwuan Metadoliolina multtvoluta Yabema gubleri Kuhfengian Neoschwagerma margaritae N. craticulifera
Midian
._~
Chuvashov, 1993 in Jin et al., 1997
Palaeofusulina Condonofuswlla
slnensIs
i Tartarian
Artinskian
Vietnam
Thailand
=
Iwaizakian Lepidolina multiseptate Kattizawan Colantella douvillei Monodwxolina matsubaishi Misellina claudine
Xiangboan N. simplex Cancelhna ne oschwagerinoides Luodianian Mtsellina claudiae Brevaxina dyhrenfurthi Longlinian Panurina darvastca Darvasites ordinatus Zisonglan Robustoschwagerina schwellwiem R.ziyunensis Sphaeroschwagerina moellert Svulgaris Pseudoschwagerina muongthensts
9
Ne oschwagerma Verbeekina Parafusulina
Kabayama
N 9 9
E
Pseudofusulina fusiformis p. vulgaris (s. l) Kuwaguchi Rugosofusilina alpina Zelha nunosel
Minato et al., 1965 in Dickins (1990) [35] Sheng & Jin (1994) [24]
Lepidolina Neoschwagerina Cancellina
Pseudofusulina slameilsls
Pse udoschwagerma talensis Robustoschwagerina Triticites suzukit
R.Invagat - Helmck (1994) [281
Misellina Robustoschwagerina Pseeudofusulina Pseudoschwagerina Schwagerina
This paper
107
for example, suggest an unconformity might be present at this level. In the Malayan Peninsula, the Chuping Limestone is generally regarded as equivalent to the Rat Buri Limestone. It is structural relationships, however, are not at all clear. Metcalfe [34] has argued that the collision occurs at the Permian- Triassic boundary inferring a major period of tectonism at this time because of a lower order of folding associated with the Bentong - Raub Suture in the Triassic compared with the Permian. Whether this is a local or general future from the existing evidence is an open question and why the folding in Central Thailand should not also represent a collision requires an answer. A threefold subdivision of the Permian is used in Japan: Lower, Middle and Upper Permian [35]. The lower Permian corresponds to the Lower Permian of the Russian twofold subdivision and the Lower Middle and Upper Permian correspond to the Upper one of the Russian sequence. Further the Upper Permian of Japan corresponds to the traditional Upper Permian of China. The Kanokura Series making up the Middle Permian has Misellina claudiae at its base according to Ozawa [36] and has marked discordance and magmaticvolcanic and tectonic activity. Reliable correlation is available with China with the boundary of the Konokura and Toyoma Series (the Upper Permian) corresponding to the Maokou Wuchiaping boundary. As in China (and Vietnam) in Japan this boundary is associated with complex volcanic and tectonic activities.
CONCLUSION The newly collected data from Cambodia, Laos and Vietnam allow a varying degree of correlation of the Permian of Indochina with those of adjacent areas. The review suggests that the most suitable scale for the Permian of this region is a threefold one that can be fitted in to the framework of the traditional twofold Permian System. This scale reflects data from many groups of organisms especially the fusulinids. In this scheme, the possibility of retaining the Chihsia according to its original definition would allow using the names Yangsingian and Lopingian as Subseries names of the Upper Permian. Retention of Bolorian in the Lower Permian and Midian in the lower of the two Upper Permian Subseries is also recommended. For this, a study and comparison of critical fusulinids such as Misellina claudiae could prove to be of considerable significance.
ACKNOWLEDGEMENTS The author is very thankful to the Departements of Geology and Mines of Cambodia, Laos and Vietnam for kind support for geological surveys. Warms thanks are extended to Dr. J.Dickins, Prof. Yin Hongfu and Dr. Guang R.Shi for very valuable discussions.
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11. 12. 13. 14.
H. Mansuy, Faunes des calcaires ~. Productus de i'Indochine, 1e serie. Mere. Serv. Geol. Indoch, Vol II, fasc. 4, Hanoi (1913), 137 pp. J. Fromaget, L'Indochine frangaise, sa structure geologique, ses roches, ses mines et leur relation possible avec la tectonique. Bull. Serv. Geol. Indoch, Vol XXVI, fasc. 2, Hanoi (1941), 140 pp. E. Saurin, Les Fusulinides des calcaires de Kylua, Langson. Bull. Serv. Geol. Indoch, Vol XXIV, fasc. 5, Hanoi (1950), 36 pp. E. Saurin, Indochine. In Lexique stratigraphique Internationale. Centre Nationale de la Rech. Scient., Paris (1956), 140 pp. A.E. Dovjikov (ed) et al, Geology of Vietnam. Explanatory note to the geological map of North Vietnam, Hanoi (1965) in Vietnamese, 584 pp. Phan Cu Tien, Upper Permian- Lower Triassic sediments in Northwest Vietnam. Nhung van de dia chat TBVN, Hanoi (1977), in Vietnamese, 109 - 151. Phan Cu Tien (ed) et al, Geology of Cambodia, Laos and Vietnam. Explanatory note to the geological map of Cambodia, Laos and Vietnam, 2 nd edition, Hanoi (1991), 156 pp. Phan Cu Tien and J. Dickins, Subdivision and correlation of Permian Stratigraphy of Vietnam and adjacent regions of Southeast Asia anf Eastern Asia. Journ. Geol. Series B, Vol. 5-6, Hanoi (1994), 3747. Nguyen Van Liem, On the stratigraphic subdivision of the Upper Paleozoic in the 1:500.000 geological map of North Vietnam. Dia chat, Vol. 74, Hanoi (1967), in Vietnamese, 6 - 8. Nguyen Van Liem, The Bacson Series of Vietnam. Stratigraphic correlation between sedimentary basins of the ESCAP region. Min. Res. Dev. Series 45, United Nation, New York (1979), 62 pp. Le Hung, New data on the biostratigraphy of Upper Paleozoic in North Vietnam. Tuyen tap Khoa hoc ky thuat, Hanoi (1975), in Vietnamese, 142- 183. Le Hung, Permian stratigraphy in Vietnam and its correlation with equivalent formation in Indochina.
Proc. 1st Conf. Geol. Indoch., Hanoi (1986), 89-100. 15. Tran Duc Luong and Nguyen Xuan Bao (eds) et al, Geological map of Vietnam, 1:500 000 scale, Hanoi (1988). 16. Vu Khuc and Bui Phu My (eds) et al, Geology of Vietnam. Vol. 1. Stratigraphy, Hanoi (1988), in Vietnamese, 174 - 214. 17. G. Shi and S. Shen. A Changhsingian (Late Permian) brachiopod fauna from Sonla, Northwest Vietnam. Journal of Asian Earth Sciences, Vol. 16, n o 5-6, (1998) 501 - 511. 18. Tran Thi Chi Thuan, Les brachiopodes permiens de Camlo. Ann. Fac. Scient., Univ. Saigon (1962), 485498. 19. J. Gubber, Etudes geologiques darts le Cambodge Occidental. Bull. Serv. Geol. lndoch., Vol XXII, fasc. 2, Hanoi (1935), 176 pp. 20. BRGM, Cartes geologiques de reconnaissance du Cambodge ~, l'echelle 1:200.000 et les notices explicatives. Paris (1968-1972). 21. H. Fontaine et al, The Permian of Southeast Asia. CCOP. Tech. Bull., Vol 18 (1986), 171 pp. 22. B.K. Tan and T.T. Khoo, Review of the development in the Geology and Mineral resources of Malaysia and Singapore. Proc. 3 rd Reg. Conf. Geo SEA, Bangkok (1978), 655-671. 23. S. Bunopas, The regional stratigraphy, paleogeographic and tectonic events of Thailand and continental Southeast Asia. Stratigraphic correlation of Southeast Asia, Bangkok, (1994), 2-14. 24. Y, Jin, J. Utting and B. Wardlaw (eds) et al, Permian Stratigraphy, Environment and Resources. Vol.l: Paleontology & Stratigraphy, Nanjing (1994), 262pp. 25. Y. Jin et al, Permian chronostratigraphic subdivision. Episodes, Vol. 20, n~ (1997), 10-15. 26. C. Mouret, Geological history of Northeastern Thailand since the Carboniferous relation with Indochina and Carboniferous- Early Cenozoic evolution model. Stratigraphic correlation of Southeast Asia, Bangkok (1994), 132-158. 27. O. Chinoroje and M. Cole, Permian carbonates in the Dao Ruang #1 Exploration Well- Implications for Petroleum Potential, Northeast Thailand. Intern. Conf. Geology, Geotechnology and Mineral Resources of Indochina, Khon Kaen (1995), 563 - 576.
109
28. 29. 30. 31. 32. 33. 34. 35. 36.
R. Invagat-Helmck, Paleozoic paleontological evidence of Thailand. Stratigraphic correlation of Southeast Asia, Bangkok (1994), 43 - 54. D. Helmck and H. Lindenberg, New data on the Indosinian orogeny from Central Thailand. Geol. Rdsch. Vol. 72, n ~ 1 (317 - 328). S. Chantaramee, Tectonic synthesis of the Lansang area and discussion of regional tectonic evolution. Proc. Reg. Conf. Geo SEA, Bangkok (1978), 177 - 186. T. Thanasuthipitak, Geology of Uttaradit area and its implication on tectonic history of Thailand. Proc. Reg. Conf. Geo SEA, Bangkok (1978), 187 - 197. O. Dawson, Fusuline foraminiferal biostratigaphy and carbonate facies of the Permian Ratburi limestone, Saraburi, Central Thailand. Jour. Micropalaeontology, Vol.2 (1993), 9-3. O. Dawson et al., Permian foraminifera from Northeast and Penisular Thailand. Stratigraphic correlation of Southeast Asia, Bangkok (1994), 323 - 332. I. Metcalfe, Gondwana dispersion and Asia accretion. Journ. Geol. Series B, Vol. 5 - 6, Hanoi (223 267). J. Dickins, Permian of Japan and its significance for world understanding. Proc. Shallow Tethys 3, Sendal (1990), 343 - 353. T. Ozawa et al., Biostratigraphic zonation of Late Carboniferous to Early Permian sequence of the Akiyoshi Limestone Group, Japan and its correlation with reference section in the Tethys region. Proc. Shallow Tethys 3, Sendal (1990), 327 - 341.
The Permian correlation
of Vietnam, Laos and Cambodia
99
and its interregional
Cu Tien PHAN Research Institute of Geology and Mineral Resources, Thanhxuan, Hanoi, Vietnam
The newly obtained research results allow correlation of the Permian of Indochina with those of China and other regions although with varying confidence. The clearest boundary in the local Permian stratigraphic scheme has been assigned to the base of the Dzhulfian formations. Some new data allow determination of a boundary at the base of the Permian and possibly the Upper Carboniferous - Permian. In Indochina, the fusulinids are of special significance because of their common occurrence and rapid evolution; however the contribution of data from other groups of organisms is and will remain of great significance. Lower and Upper Permian could be retained as series of the Permian according to their general usage and subseries can be recognized in the Upper Permian of Indochina Peninsula and adjacent territories of Southeast Asia and Eastern Asia.
1. I N T R O D U C T I O N This paper will not deal with the whole Indochina Peninsula. It is concerned mainly with Cambodia, Laos and Vietnam, the Indochina countries; however the Permian formation of the three countries will be correlated with those of Thailand, Malaysia of Indochina Peninsula and South China, Japan as well. The first description of the Permian formation of Indochina were presented in the beginning of this century. These are Productus Quartz Sandstone, Fusulinid-bearing Limestone and others [1, 2, 3]. Relating to the tectonostratigraphic interpretation, Fromaget considered the Permian formations of Indochina as parts of Anthracolite Limestone or Indosinias Terrigene [4]. In the view of stratigraphic correlations. Saurin classified the Permian formations into Artinskian, Kungurian, Kazanian, or some fusulinid horizons [5, 6]. Since 1954, in the geological publications, the Permian formations of Vietnam and its relationship with the Carboniferous were described as a monotonous sequence belonging to the "tectonic leveling" of the territories [7]. However on the basis of newly collected data, Permian formations of Vietnam in particular and Indochina Peninsula in general were recognized to be complicated with various composition and abundant mineral resources[8-10]. In the geological development of Vietnam and adjacent territories, the Permian geological events accompanying the change of structural framework, palaeogeography and volcanic
100 activities have been identified.
2. P E R M I A N
VOLCANO
- SEDIMENTARY
FORMATIONS
In Indochina, the following stratigraphic regions have been classified in the geological map of Cambodia, Laos and Vietnam: Vietbac, West Bacbo, Truongson, Kontum Savannakhet, Dalat Stungtreng and Northwest Laos [9]. These regions are separated from the West Thailand region by the Nan Suture (Fig. 1). In the Vietbac, the lower part of Permian is characterized by monotonous, black, grey limestone corresponding to the upper part of the Bacson Formation of Carboniferous Permian. The definition of Permian is mainly based on Schwagerina or Robustoschwagerina, Misellina, Cancellina, Neoschwagerina, Lepidolina - Yabeina horizons of Asselian - Midian [11-15]. Here, the Dongdang Formation of D z h u l f i a n - Darashamian age overlies unconformably on the eroded surface of the above mentioned limestones and comprised basal bauxite beds, shale, chert and limestone. The limestones contain Codonofusiella aff. paradoxa Dunbar et Skinner, Dunbarella sp. in the lower part and Palaeofusulina prisca Deprat, Colaniella parva (Col.), Reichelina pulchra M. Maclay, Neoendothyra eostaffelloidea Liem and Leptodus sp., in the upper part. The Lower Triassic sandstone, silstone containing Claraia, Glyptophiceras overlies the above - mentioned formation with an either conformity or a disconformity [16]. In some places such as Baichay, the Upper Permian comprise quartzite, shale, chert and coal seams. The collected fossils are Meekella cf. ufensis Tchernyshev, Lyttonia sp., Productus gratiosus Waagen, Martiniopsis aff. orientalis Tchernyshev, Spiriferina cambodgiensis Mansuy, Pseudomonotis cf. garforthensis King, Pseudophillipsia cf. acumulata Mansuy,... [1 ]. In the West Bacbo region, the Permian sedimentary sequence is presented mainly by the Lower Permian and may be Upper Carboniferous as well (Table 1). In the southwestern periphery of the region, at Thanhhoa area, the Lower Permian limestone continuous from the Upper Carboniferous limestone; however the Upper Permian mafic volcanics of the Camthuy Formation overlies unconformably the older formations. The formation is composed of volcanics belonging to the picrite - basalt association, 700 - 800m thick. Overlying the mafic volcanics, there are shale, chert, coal shale, coal seams, limonite, hematite beds in places and limestone of the Yenduyet Formation. The thickness of the coal seam varies, from 20 - 30 cm to 6 m. Limonite, hematite beds have the thickness of 3 m, Fe203 varies from 23 - 37% to 62% in places, A1203 22 - 23%, SiO 2 12-17%. The collected fossils in shales comprises Leptodus sp. (cf. L. nobilis Waagen), Squamularia sp., Schellwienella sp., Chonetes sp., Actinodesma sp., Spiriferella sp., Neophricodothyris cf. asiatica Chao and Aviculopecten sp., Oldhamina sp., Marginifera cf. lopingensis (Kayser), Andersonoceras sp., Pseudotirolites sp., Gigantopteris sp., Pterophyllum sp. [18] and Chonitipustula sp., Dielasma sp., Productus (Alexenia ?) sp., Chonetes sp., Spirifer sp., [7]. Similar sections also crop out in Sonla, Laichau along the eastern periphery of the Songma anticlinorium, the collected fossils comprise Peltichia kwangtungensis (Zhan), Acosarina minuta (Abich), Rhipidomella hessensis King, Schuchertella cf. cooperi Grant, Derbyia sp., Waagenites soochowensis (Chao), Spinomarginifera chenyaoyanensis Huang, Marginifera gen. et sp. indet. [17]. The relationship between the Upper Permian and Lower Triassic is conformity or disconformity.
101
4-,'"
%%
!
!
VIETBAC
"~
! Ph~
SONLA BACBO
Sl
NORTHWEST
,
LAOS
CHINA
tx x
Bacson
HOABINH
Ikhay
/
/
Luongphabang
Muongxen ~ ~'%,.,,~,% % % TRU~N~G
[ / ,I,..-, .,-",_VIENTIANE '~%%,.,,#$
'
SON..,.
%~%%
Loei
X% \
i !
x
x\ SAVA x NAKHET
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! I ! I
X
/ ,O.TUM \
.1 Ratburi BANG K
/
/
/
"~
~
\
\
Sis
I
Pursat
4.~ i~.../" ..,, /
DALATf
X.,j Tathiet
L/F------150 I
75 I
0 I
75 I
150 I
225 I
300 Ikm
Figure 1. Stratigraphic Regions of Cambodia, Laos, Vietnam (main land) and adjacent regions. VIETBAC
Stratigraphic region name
/
i
Deep - seated fault
102 In the Da river valley, mafic volcanics have great thickness, various composition and are closely related to ultramafic and mafic intrusions. It seams possible to define 3 magmatic associations from the lower part to the upper part of the section. These are picrite basalt andesite association closely related to the picrite diabase association; basalt komatiite and trachydacite, trachyandesite basalt association. The above association underlie siltstone, shale, marl, sandstone of the Lower Triassic (Olenekian). In the picrite basalt of the picrite basalt andesite association, the percentage of basalt reaches 70 - 80%. According to the petrochemical characteristics, these rocks are rather highly alkaline and high in TiO2. Total alkaline reaches 3% in subultramafic and 3.6% in mafic intrusion; TiO2:1.8 and 2.2 respectively; K20/Na20: 0.38; A1203:8.4 - 24 and FeO: 8.4 -
14%.
Pertaining to the picrite diabase association, there exist dike, veins and subvolcanic bodies of peridotite, picrite diabase and gabbro ophyte belonging to the ultramafic, ultramafic - mafic and mafic groups. The ultramafic group is characterized by low alkalinity. Na20 + K20 < 1%; TiO2 < 1; A1203:5.17 - 5.56; relatively high MgO: 3.0 - 4.5%; Na is predominant. Basalt komatiite association is recently defined in the center of Da river valley and composed of komatiitic peridotite (20 - 40% MgO), komatiitic basalt (12 - 20% MgO), olivine bearing basalt rich MgO and leucocratic basalt (< 8% MgO). Petrochemically, the association is characterized by TiO2:0.12 - 0.19; CaO/A1203:0.8 - 1.1; CaO/TiO2:14.4 - 21.5 and A1202/TiO2:18.3 - 23.4%. The trachydacite-trachyandesite-basaltoid association crops out mainly in the eastern periphery of the region and seems to be of Permian and Permian-Triassic age. This association is characterized by high alkaline, alkaline and subalkaline rocks, SiO2:49.4 - 67.5; TiO2:0.7 - 3.7; A1203: 14; MgO: 0.4 - 6.3; CaO: 1.1 - 8.3%; total alkaline > 4%, among them K > Na in trachyandesite. The contacts between the volcanic formations and other ones are mainly tectonic. The intercalation of sedimentary and volcanic rocks can be seen in some places such as the Hoabinh hydroelectric dam site. In ascending order this section comprises of: 1) basaltic porphyrit, 20 m thick; 2) limestone, marl, 20 m thick; 3) carbonate siltstone containing badly preserved brachiopods, 10 m thick; 4) limestone containing Triticites (?) sp., Pseudofusulina sp., Misellina ovalis Deprat, 20 m thick; 5) basalt, tuffs, 17m thick; 6) sandstone, siltstone, marl containing Ditomopyge sp., Aulacorhyncus protechwensis Grabau et Tien,
Propinacoceras aff. aktubense Rhyzhensev .... 15m thick; 7) limestone containing Misellina ovalis (Deprat), Neofusulina sp., Pseudofusulina sp., 30 m thick [8]. In the Truongson region, Permian and Carboniferous limestones crop out in continuous sections at Quydat, Muongxen of Vietnam and Nonghet, Khammoun, Vangvieng of Laos. Permian limestone contain abundant fusulinids corresponding to the Schwagerina, Robustoschwagerina, Misellina, Cancellina and Neoschwagerina horizons. Uppermost part of the Permian have been observed in places. At Khegiua area, limestones contain Codonofusulina nana Erk, Neoendothyra eostaffelloidea Liem, Palaeofusulina (?) sp., Reicheline (?) sp. [13], and at Camlo area, shales contain Leptodus nobilis (Waagen), Chonetes subtrophomenoides Huang and Meekella kweichowensis Huang [18]. The relationship between the above limestones and older formations is not defined yet. The Permian volcano sedimentary formation of this region is restricted to the narrow band along the fault in Alin area of Vietnam and enlarged in Khangkhay area of Laos. Along the
103 road N017 from Phonsavan to Khangkhay, the formation is composed of grey shale, marl containing Plicatifera sp., Schuchertella sp., Anarsalites sp. of the lower part; red coloured carbonate, siltstones, sandstones of upper part [9]. In the Dalat Stungtreng region, the Daklin Formation of the Upper Carboniferous-Permian crops out in the same name in Vietnam and comprises shale, chert, andesite, basaltic andesite in the lower part; andesite, tufts, sandstone in the middle part; and andesite, basaltic andesite, dacite, rhyolite, marl, limestone in the upper part. The collected fossils are badly preserved bryozoans, crinoids, brachiopods in shale and Sschwagerina sp., Pseudofusulina sp., Verbeekina sp. in the limestone. The volcano-terrigenous formations distributed in the Stungtreng, Preah Vihear, Siemreap of Cambodia can be correlated with those in the Daklin area. The intercalations of volcanic rocks and limestone were observed in the right band of Mekong River, North of Stungtreng, in Chhep and Stungtreng [19, 20]. Permian limestones crop out in Hatien of Vietnam, Campot, Phnomxa and Battambang of Cambodia. The Hatien Formation in Vietnam is characterized by limestones containing Verbeekina verbeeki Genitz, Neoschwagerina margaritae Deprat, Codonofusiella sp., Parafusulina sp., Nankinella sp. and gastropods, rugose corals and crinoids [9, 16]. In Phnomxa of Cambonia, the Permian formation is composed of: 1) basal conglomerate containing fragments of quartzite, sandstone, rhyolite; 2) oolitic limestone; 3) fossiliferous marl, limestone; 4) siliceous limestone containing sponge and radiolarians; 5) massive limestone [ 19]. According to Dottin and Langle [20], the Permian stratigraphic scheme of Cambodia is composed of: 1) limestone containing Yangchienia and Cancellina of Artinskian age; 2) limestone containing Praesumatrina dunbari in Phnom Svai and Verbeekina verbeeki, Neoschwagerina douvillei in Battambang of Kungurian age; 3) limestone containing Yabeina and Lepidolina of Kazanian age; 4) limestone containing Brachiopoda in Battambang of Upper Kazanian and 5) limestones schists in Svaycheck of Tartarian age. The uppermost part of Permian crops out in Tathiet, at the Cambodia-Vietnam border and comprises siltstone, sandstone, shale containing Streptorhyncus cf. perlargonatus (Schlotheim), Uncinunellina sp. (aff. U. timorensis Beyrich), Giriypecten sp., Palaeolima sp. in the lower part and limestone containing Palaeofusulina prisca (Deprat), Colaniella parva (Col.), Reichelina pulchra M. Maclay, Neoendothyra dondangensis Liem in the upper part. The above-mentioned sediments conformably underlie sandstone, siltstone containing Claraia, Otoceras (Motococeras) of the Triassic [ 16, 21 ]. Except the carbonate terrigenous formations, andesite, rhyolite, tufts, aglomerate in Honchong of Vietnam and in Campot of Cambodia were classified into Permian-Triassic in the correlation with those in West Thailand and Malaysia [22, 23]. In the Northwest Laos region, the Songda Formation at the Muongte area of Vietnam is made of coglomerate, sandstone, shale, chert, andesite, rhyolite and limestone containing Pseudofusulina sp., Parafusulina ex gr. japonica (Gumb.), Misellina ex gr. ovalis (Deprat) and Chonetes sp. [7, 9]. In the territory of Laos, the Permian formations comprise also sandstone, shale, tufts and limestone containing Orthoceras sp., Griffitides sp., Productus aagardi at Sayabuli and Pseudofusulina japonica, P. gigantea at Nambac valley [5]. In this region, Fromaget [4] described a coal-bearing formation of Permian age at Soppong. Here, sandstone, shale and coal-shale contain Gigantopteris nicotinaefolia, Cordaites cf. Principalis and Schizoneura gondwanensis. The relationship between the Permian volcanosedimentary, carbonate and coal-bearing formations has not been defined yet.
Table 1 9 Permian Stratigraphic Correlation of C a m b o d i a , Laos and V i e t n a m Dalat
- Stungtreng
Truongson
West Bacbo |
Hatien, Battambang
Tathiet
West Hue, Xiengkhoang
Daklin, Stungtreng
Quydat, Nonghet
Lower Triassic:
Lower Triassic i
Sonla, Thanhhoa
Vietbac Vanyen, Hoabinh Lower Triassic 9
Otoceras
Claraia and
Costatoria and
Clarata, Lingula
(Metotoceras) and
Lytophiceras ....
Eumorphotis ....
and Glyptophiceras ....
....................... Yenduvet Formation
Lobatannularia,
Dongdang Formation
Palaeofusulina and
Pecopteris,
Palaeofusulina and
CodonofusieUa Horizons
Gigantopteris ....
Codonofusiella
Leptodus Chonetes and Gigantopteris, ...
Volcanics
Claraia .... i 9- - - . - - ~ - P e r m i a n - Triassic i Volcanics
...................
Permian - Triassic
Camlo s h a l e s
Volcanics
Leptodus, Chonetes
9
and Dyctyoclostus .... .....................
Tathiet Formation
..................
Palaeofusulina Horizon
Viennam Formation
Horizons Leptodus
Volcanics
Upper pa~ of
!
Hatien (Battambang)
A l i n (Khangldaay)
Formation:
Lepidolina and
Daklin Formation
Neoschwagerina
Verbeekina
Horizons
Pseudofusulina and Schwagerina (?) .... Volcanics
Muonglong
Upper part of
(Nonghet) Damai Formation :
Bandiet Formation
Bacson Formation :
Formation 9
Formation:
Neoschwagerina,
MiseIlina, and
Neoschwagerina,
Plicatifera, Anatsalites
Neoschwagerina,
Misellina,
Robustoschwagerina
Misellina,
and Schuchertella ....
Cancellina, Misellina, Robustoschwagerina and
Horizons
Robustoschwagerina
Volcanics
Robustoschwagerina and
Propinacoceras
and Schwagerina Horizons
Schwagerina Horizons
Schwagerina Horizons
Schwagerina ,,--"""
?
Upper part of
Neoschwagerina,
"rtticttes Horizon
...'"""" Horizons
Titicites Horizon
Triticites Horizon
105 3. S T R A T I G R A P H I C C O R R E L A T I O N OF PERMIAN FORMATIONS. The newly obtained data in Cambodia, Laos and Vietnam allow a correlation of Permian formations of the three countries with those of South China and adjacent regions although with different confidence. In the Vietbac region, the boundary between the Neoschwagerina-bearing limestones of the Bacson Formation can be correlated with the base of the Wuchiaping Formation of the Lopingian Series or the top of the Maokou Formation of the Yangsingian Series [24]. The latter have been correlated with the Guadalupian Series [25]. In the West Bacbo, the mafic volcanics of the Camthuy Formation is easily correlated with the Omeishan Basalt Formation in Yunnan and Guizhou of China although their origins may be complicated. The Yenduyet Formation may correspond to two formations of Lopingian Series and the volcanics of Bandiet Formation are also correlatable with those of the Maokou Formation in the above-mentioned provinces of China (Table 2). For long, in China the lower boundary of the Permian has been placed at the base of Chihsia Formation containing Misellina claudiae which was originally defined in the Nanjing area where the formation lies with a hiatus on older beds [24]. This practice has also been followed in Vietnam [ 14, 15]. More recently practice has tended to look for a Lower Permian basal boundary equivalent to the base of the Asselian as used in the Ural area and many other parts of the world. The traditional subdivision is thus rather in a state of flux. As discussed below a return to the orginal definition of the Chihsia has a potential for a clearer correlation with Japan and the two subdivisions of the Upper Permian (for a twofold Permian System), the Yanghsingian and Lopingian [ 10]. The geological events at the top of the Bacson Formation in the Northeast and West Bacbo of Vietnam or the Maokou Formation in the Yunnan and Guizhou of China seem to be unclear in the Truongson and Dalat Stungtreng regions. Fromaget [4] recognized the Moscovian geological event in Indochina. However it is unconfirmed by recent investigations. Some newly obtained data in Vietnam and in Laos allow determination of boundary at the base of the Khangkhay, Daklin and possibly Hatien Formation. May be, this boundary coincided with the boundary in Upper Carboniferous-Permian in the regional column of Khorat Plateau [26, 27]. The Tathiet Formation at the uppermost part of the Saigon river can also be correlated with the limestones in the Doi Pha Pleung, Amphoe Ngao and Changwat Lampang areas and in some other places [28]. The Permian - Triassic Honchong Formation may also be equated with the volcanic sequences of the same age in Thailand and Malaysia [20, 22]. Considerable progress has recently been made in Central and Western Thailand. In Central Thailand, strong folding and orogenic activity with flysh formation has been described in the Kubergandian- Midian [29]. In Western Thailand, an unconformity seems to present at the base of the Permian or Upper Carboniferous sequences. However the detailed descriptions and age remain unclear [30, 31]. In most recent publications [32, 33], a local subdivision of the Permian has been used, in which the Lower Permian remains poorly known, the rest being composed of Kubergandian and Murgabian belonging to Middle Permian and the Midian together with the Dzhulfian and presumably the Dorashamian and equivalents belonging to Upper Permian. Whether the Midian-Dzhulfian event is present in Thailand as found in Vietnam, China and Japan is thus unclear. The Middle Permian, however, is apparently represented in the beginning of the orogenic event in the Kubergandian, and Dawson [32, 33]
Table 2 9 Stratigraphie Correlation of Permian in Vietnam and Adjacent Regions Traditional standard Southern
Proposed classifi cation of SPS
Urals
Changhsinglan
Armenia Iran, Pamir
South China Changhsingian Palaeofusuhna smensls P. minima Gallowaynella meitwnsis Wuchiapin~oian Nankinella simplex Codonofuswlla kwangstensts
Darashamian
-~o Wuchiapingmn
Dzhulfian
South Kitakami, Japan
Nabekoshian Palaeofusulina sp.
~o G
Maehaman
Lepidolina kumaensis Lepidohna kumaensts
i
Palae@r Gallowaynella Colaniella Codonofuslella E
Capitanian
Wordian
Kazanian
Ufimian
Roadian
Kungurian
Kungurian
.~
Artinskian
Murgabian
Kubergandianian
Blorian
Yakhtanshian
Sakmarian
Sakmarian
Sakmarian
Asselian
Asselian
Asselian
[251
Jin et al (1997)
[251
Kotlyar, 1987 Leven et al, 1993 in Jin et al., (1994)
[241
=
~:~ >-
y.
Lengwuan Metadoliolina multtvoluta Yabema gubleri Kuhfengian Neoschwagerma margaritae N. craticulifera
Midian
._~
Chuvashov, 1993 in Jin et al., 1997
Palaeofusulina Condonofuswlla
slnensIs
i Tartarian
Artinskian
Vietnam
Thailand
=
Iwaizakian Lepidolina multiseptate Kattizawan Colantella douvillei Monodwxolina matsubaishi Misellina claudine
Xiangboan N. simplex Cancelhna ne oschwagerinoides Luodianian Mtsellina claudiae Brevaxina dyhrenfurthi Longlinian Panurina darvastca Darvasites ordinatus Zisonglan Robustoschwagerina schwellwiem R.ziyunensis Sphaeroschwagerina moellert Svulgaris Pseudoschwagerina muongthensts
9
Ne oschwagerma Verbeekina Parafusulina
Kabayama
N 9 9
E
Pseudofusulina fusiformis p. vulgaris (s. l) Kuwaguchi Rugosofusilina alpina Zelha nunosel
Minato et al., 1965 in Dickins (1990) [35] Sheng & Jin (1994) [24]
Lepidolina Neoschwagerina Cancellina
Pseudofusulina slameilsls
Pse udoschwagerma talensis Robustoschwagerina Triticites suzukit
R.Invagat - Helmck (1994) [281
Misellina Robustoschwagerina Pseeudofusulina Pseudoschwagerina Schwagerina
This paper
107
for example, suggest an unconformity might be present at this level. In the Malayan Peninsula, the Chuping Limestone is generally regarded as equivalent to the Rat Buri Limestone. It is structural relationships, however, are not at all clear. Metcalfe [34] has argued that the collision occurs at the Permian- Triassic boundary inferring a major period of tectonism at this time because of a lower order of folding associated with the Bentong - Raub Suture in the Triassic compared with the Permian. Whether this is a local or general future from the existing evidence is an open question and why the folding in Central Thailand should not also represent a collision requires an answer. A threefold subdivision of the Permian is used in Japan: Lower, Middle and Upper Permian [35]. The lower Permian corresponds to the Lower Permian of the Russian twofold subdivision and the Lower Middle and Upper Permian correspond to the Upper one of the Russian sequence. Further the Upper Permian of Japan corresponds to the traditional Upper Permian of China. The Kanokura Series making up the Middle Permian has Misellina claudiae at its base according to Ozawa [36] and has marked discordance and magmaticvolcanic and tectonic activity. Reliable correlation is available with China with the boundary of the Konokura and Toyoma Series (the Upper Permian) corresponding to the Maokou Wuchiaping boundary. As in China (and Vietnam) in Japan this boundary is associated with complex volcanic and tectonic activities.
CONCLUSION The newly collected data from Cambodia, Laos and Vietnam allow a varying degree of correlation of the Permian of Indochina with those of adjacent areas. The review suggests that the most suitable scale for the Permian of this region is a threefold one that can be fitted in to the framework of the traditional twofold Permian System. This scale reflects data from many groups of organisms especially the fusulinids. In this scheme, the possibility of retaining the Chihsia according to its original definition would allow using the names Yangsingian and Lopingian as Subseries names of the Upper Permian. Retention of Bolorian in the Lower Permian and Midian in the lower of the two Upper Permian Subseries is also recommended. For this, a study and comparison of critical fusulinids such as Misellina claudiae could prove to be of considerable significance.
ACKNOWLEDGEMENTS The author is very thankful to the Departements of Geology and Mines of Cambodia, Laos and Vietnam for kind support for geological surveys. Warms thanks are extended to Dr. J.Dickins, Prof. Yin Hongfu and Dr. Guang R.Shi for very valuable discussions.
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