V N U J O U R N A L O F S C I E N C E , N a t S c i & T e c h , t.X V III, n ° l - 0 O R D O V IC IA N - S IL U R IA N A N D L O W E R D E V O N IA N G R A P T O L IT E B E A R IN G BEDS FR O M V IE T N A M N g u y e n V an P h u c Faculty o f Geology, College o f Natural Sciences - VNU INTRODUCTION Ordovician and Silurian graptolite bearing beds from V ietnam were firstly described by Giraud J (1918) and P a tt E (1927) but the Lower Devonian graptolite bearing beds were discovered by Nguyen Van Phuc only in 1994 These s tra ta were then briefly described from 1965 to 1989 Detailed work on graptolite bearing beds was carried out by Nguyen Van Phuc when he measured the sections in Northern and C entral Vietnam , during 1978 to 1995 (Fig and Fig 2) The present paper gives an account of the im portant Ordovician - Silurian and Lower Devonian graptolite zones and horizons of the newly discovered graptolite fauna Based on these species and forms, a primitive Ordovician - Silurtian and Lower Devonian graptolite sequence in Vietnam is configured It allows the author to review the recently established stratigraphical units STRATIGRAPHY Lower Palaeozoic and Lower Devonian rocks from Central Vietnam are character ized by the deeper water elastics with typical black graptolite bitum inous shales, but in the weathering they are variably coloured However, shallow w ater deposits including car bonate and shallow water clastics are dom inant both in N orthern and C entral Vietnam Since the andesites and lydites which intruded in the Caradocian and Ashgilian graptolite bearing beds in Central Vietnam, it is possible th a t Ordovician ophiolites could exist and thus would indicate an Ordovician suture zone in Central V ietnam Thus, two blocks, the south margin of the C athaysian massif (Northern V ietnam ) and north m argin of the Indosinian massif (Southern Vietnam) were separated by the Central V ietnam suture zone during Ordovician, Silurian and Lower Devonian I C e n tra l V ie tn a m Q ue T an - D a i Q u a n g a re a The studied sections belong to the A Vuong Formation It was described by Nguyen Xuan Bao (1979) and named after the A Vuong River and may indicate as an age of Late Cambrian - Early Ordovician, but it is unfossiliferous Therefore the age of the formation is further discussed The unit is localated in the south of the Bach Ma M ountain The sections are composed of variegated coloured mudstones, carbonate mudstones, shales, sandstones, quartzites, and conglomerates, at the base intercalated with andesites and limestone lenses T y p e se t b y ẨyVtS-TgX O rd o v ic ia n - Silu rian a n d lo w e r D e v o n ia n h p to lite bearing with a total thickness of about 1500 m Early Ordovician graptolites were collected by Nguyen Van Phuc from the middle part of the formation 102 ° 104° 106 ° 108 ° 110° Fig Lacality map of the Ordovician - Silurian and Early Devonian graptolites in Northern and Central Vietnam ■ Solid rectangle: Localities of Ordovician graptolites • Solid circle: Localities of Silurian graptolites ^ Solid triangle: Localities of Early Devonian graptolites The Studied sections: Daiquang - Que Tan sections, Khesoc - Tatrach sections, Namdong pass section.4 Huongdien - Dong Ngo sections, 5-6-7-8-9.DongHa sections, 10-11-12-13-14-15 Longdai sections, 16 Leky section, 17-20 Northern Muong Xen sections, 21 Phugu section, 22-23 Chodon sections, 24 Namo section, 25 Nazam section, 26 Coto sections, 27 Tanmai section N g u y e n V an P h u c Graptolite Zones Northern Muongxen Namdong pass M yukonensis Upper part Middle part M hercynicus M unrformis Longdai R Longdai R 1252 P-L' M lochkovensis Pris uttimus M formosus Tanmai M.cf.uncmatus beds bohemicus-chimaera Pfis vulgaris Dongha, Tanlam M cf priodon beds centrifugus-murchisom Nazam Sp spiralis griestoniensis-crenulata Phungu turriculatus-exiguus sedgwickii convolutus argenteus S9215c ill 9215b Iriangulatus-greganui 9215a Cor cyphus vesiculosus-atavus Par acuminatus G persculptus Dip bohemicus Namo Khesoc Huongdien, Tatfach Dongngo Die gurleyi beds Que Tan LI austrodentatus or -Did, ldentuspsfls J1758 K6732 Did abnormis beds Daiquang D flabelliforme beds © _ Interbeds of shales K M Graptolite zone E==3 mudstones and ■, jzz.z: sandstones Suggested zone Quartzites Qj gg| §§§21 Graptoliie beds Sandstones m Limestone lenses f Graptolites Gravelites Silicious rocks Conglomerates Silicious shales £ other fossils Limestones Reticular and nodular limestones Sericite shaies + Plants Shales Fig Ordovician, Silurian,Lower Devonian graptolite zones and beds in Northern đnỏ Central Vietnam O rd o v ic ia n - Silu r ian a n d lo w e r D e v o n ia n h p to lite bearing 41 From the Dai Q uang section (section la , Dai Loc- District, Quang Nam - Da Nang Province): D jia b e llifo r m e q r a p to lith in u m b e d s (L ow er T re m a d o c ia n ) Loc HQ 507: D flabdliform c graptolithinum Kjrulf A sinensis Hsu, p plumosus Hall From the lower part of Que Tan section (section lb , Que Son D istrict), which is localated ill the south from Dai Quang section, were found questionable graptolites N a m D o n g a r e a (T hua T hien Hue Province) The measured sections belong to the same A Vuong Formation From Khe Soc - Ta Trach section (section 2), Nam Dong District: D id A b n o r m is b e d s (U p p e r p a r t o f A re n ig ia n , from Az Suecicus to Ex Clavus zones of China) Loc.J 2621: D id Abnormis (Hsu), Ph Anna Hall In the Jiangshan-Changshan-Y ushan area of C hina Ph Anna Hall occurs from the base of Az Suecicus zone to the top of Ex Clavus zone Did Abnorrnis (Hsu) is presented in the same level, but extended through the lower p art of the u austrodentatus zone Under these graptolite bearing beds are exposed the metamorphosed carbonate mudstones and shales with the intercalated pyrite bearing lenses of limestones u a u s tr o d e n ta tu s z o n e (U p p e r p a r t o f L la n v irn ia n ) Loc 9254: u sinodcntatus (Mu et Lee), u ex gr Forrnosus (Mu et Lee), Climacograptus sp Ill the Nani Dong area the rocks of all stratigraphycal units are exposed: andesites, rhyolit.es, carbonate m udstones and shales, deeper water and shallow water directed fault system Therefore we can not know which stratigraphycal unit is developed because no graptolites and any fossils were found as yet, and stratigraphycal relation of the andesites, rhyolites are too From the red beds of the section (section 3) near the Nam Dong Pass (at Km No to Quang Nam - Da Nang Province), there are exposed with Lower Devonian age: M o n o g p tu s b e d s (may be L ow er p a r t o f L o ch k o v ian ): Loc 9252: Monograptus sp., similar to M aequabilis group with pelecypods, gastropods, and brachiopods H u o n g D ie n a n d D o n g N g o a re a The Huong Dien section is localated in the west of Hue city, from which were collected: D id id e n tu s b e d s (U a u s tr o d e n ta tu s zone, u p p e r p a r t o f L la n v irn ia n ) Loc .1 1758: Did identus (Hall) From the Dong Ngo section (in the left bank of Ba Long River near the Ba Long Village, Ba Long D istrict, Q uang Tri Province) Loc K 7642: Did nanus Lapw D o n g H a area In 1982, 1990-1992 and during the present year, the author measured sections (sections 5-9) along the Road No from Km No to Km No 24 near the Dan Mail Bridge As a new unit the Dong Ha Formation is proposed here which is composed of sandstones, mudstones, black bitum inous variously and coloured shales in weathered state with a thickness of 900 m From these sections graptolites were collected by the author, in ascending order as follows: D ip B o h e m ic u s z o n e (A sh g ilia n , O rd o v ic ia n ) Loc DH 940, DH 984: Dip boherriicus (Marek) Am m adernii (Koren et Mikh.) 42 N g u y e n Van P h u c G p e rs c u lp tu s zo n e (u p p e rm o s t z o n e o f A s h g ilia n , O rd o v ic ia n ) Loc DH 9810: G persculptus (Salter), G gracilis Ge, Cl angustus (Perner) P a r a c u m in a tu s z o n e (R h u d d a n ia n , L la n d o v e ry ) Loc DH Í86: Par acuminatus (Nicholson) A t a ta v u s z o n e (R h u d d a n ia n , L la n d o v e ry ) Loc 8222, Loc DH 984: At atavus (Jones), Pr incommodus (Tornq.), Dip modestus Lapw C or g regarius zo n e or D e m tr ia n g u la tu s (A ero n ia n , L landovery) Loc 8217: Cor gregamus (Lapw.), N scalaris (Hising.), Loc 8223, Loc DH 982: N scalaris (Hising.), Ps hughesi (Nichol.), G tamariscus (Nichol.), L poschovae Chal., Dem triangulatus (Hark.), Cam curtus O but et Sob., Rastrites sp M sed g w ickii z o n e (A e ro n ia n , L la n d o v e ry ) Loc 8220: M sedgwichii (Port.), Cam communis (Lapw.), Ps hughesi (Nichol.), Pet palmeus (Bar.), Pet m m or Elies Pet praecursor Boucek et, Pribyl S tr ex ig u u s zo n e (T e ly c h ia n , L la n d o v e ry ) Loc 8210, Loc 829: Sir exiguus (Nichol.), M parapriodon Boucek M o n g r ie s to n ie n s is zo n e (T e ly c h ia n , L la n d o v e ry ) Loc 827, Loc 828: Mon griestoniensis (Nichol.), M priodon (Bronn), M acus Elies et Wood The upperm ost black beds of the Str spiralis zone (Telychian, Llandovery) in the Dong Ha area were not yet found until now L ong D a re a The author and his colleagues have carried out field work in the Long Dai River Valley in 1991-1992 In this area sections were m easured (sections 10-15) From these sections we discovered 39 localities of graptolites and localities of trilobites, brachiopods, crinoids and nautiloids From the middle part of the section located along the Long Dai River at Km No 28 : D ie g u rle y i b ed s (Low er C arad ocian ) Loc 9223: Die gurleyi Lapw., Die cf sextans exilis (Elies et Wood), G euglyphus (Lapw.), Climacograptus sp Die Gurleyi Lapw Die sextans exilis (E et w ) indicate the Nem gracilis and Cl peltifer zones From the Ban Ho, Ban Mit sections and section a t Km No 28: P a r a c u m in a tu s zo n e (R h u d d an ian , L la n d o v ery ) Loc 923: Dip angustidens Ge, G tam anscus linearis Perner, N norm,alls (Lapw.) Loc 92 (collected from the pebbles of the shales along the right bank of Long Dai River at Km No 28): N cf Normalis (Lapw.), N nanjingensis linearis (Park.) Loc 9241: N normalis (Lapw.), N angustus (Perrier), Par acuminatus (Nichol.), Par sinitzini (Chalet.) C ys v e sic u lo su s zon e (R h u d d an ian , L la n d o v ery ) Loc 923: Cys vesiculosus (Nichol.), Ps hughesi (Nichol.) Loc 92: Dim extenuatus E et w , Dip secundus Obut et Sob., Met jinyangensis (Ye) Loc 9231: Cys vesiculosus (Nichol.), N rectangularis (M’Coy), G sinuatus Nichol Loc 9234: N nanjingensis linearis (Park.), Dip tcherskyi Obut et Sob Met Jinyangensis (Ye) C or c y p h u s z o n e ( R h u d d a n ia n , L la n d o v e ry ) (Lapw.), Cor acinaces (Tornq.), Pr sandersoni (Lapw.) Loc 9215: Cor cyphus D em c o n v o lu tu s z o n e (A e ro n ia n , L la n d o v e ry ) Loc 929: Dem pulchern m us Manck O rd o v ic ia n - S ilu r ia n a n d lo w e r D e v o n ia n h p to lite bearing From the section along the way No 10 from Km No 21 to Km No 18: M sed q w iskii zo n e (A e ro n ia n , L la n d o v e ry ) Loc 9216: M sedqwickii (Port-1.) Pet tenuis (Bar.) Loc 9225: M sedgwickii (Port 1.), M circularis E et w Pet palmeus (Bar.) Pet praecursor Boucek et Prib Monograptus sp In tile section from Km No 21 to Km No 18: Sp tu r r ic u la tu s z o n e (T e ly c h ia n , L la n d o v e ry ) Loc 9222: Sp turriculatus (Bar.), sp m inor (Boucek) Sir filiform is Chen Pet tenuis (Bar.) Loc 9227: Sp turriculatus (Bar.) Pet tenuis (B ar.) Monograptus sp In tli M scam cus • c0 N eo mlssom _] c * N o sedim ents M lochkovensis Pns ultimus -— _ * x>uceki-transgrediens boh tenuis-kozlow skii * M y u k o n e n s is M fanicus M form osus V ie tn a m M falcarius I : _J M yukonensis M fanicus c IAN P R ID O - T h a ila n d M pacificus M falcanus Q A u s tr a lia M yuKonensis craigensis & thom asi 0) o C h in a D flabelliforme beds • C onjectural Zones Fig Comparison and correlation of Ordovician-Silurian-Lower Devonian graptolite zones and b of Vietnam and other countries in the vicinity.Cited papers of the authors: 1- Standard Silui graptolite zones, after: Koren T.N., Lenz A.C., Loydell D.K., Melchin M.J., Storch p., Teller L IS British Standard Ordovician graptolite zones, after: Skevington D., 1976, 2- Lin Bao yu et al., 1982 and Jiao, 1983; Mu and Lin Yao-Kun, 1984; Mu, 1984; Chen Xu and Quan Qiu-Qi, 1992; Chen 1995, 3- Shrrard, 1953; Thomas, 1960; Jaeger H, 1966, 1967; Jaeger and Stein, 1969; Skevington 1976,4- Kobayashi T„ Igo H„ 1965; Burton C.K., 1967, 5- Burton C.K., 1967; Jones c., 1973 O rd o v ic ia n - Silurian a n d lo w e r D e v o n ia n h p to lite bearing 4Í) R eferen ces C.K Burton G raptolite and Tentaculite correlation and palaeogeography of the Sil urian and Devonian in the Yunnan-M alaya geosyncline Trans, and Proc Palaeontol Soc Japan, N.S., No 65 (1967) pp 27-46 Chen Xu Regional S tratigraphy and Paleogeography In Chen X u and Bergstrom S.M Nanjing University Press, Nanjing China, 1995 pp.7-13 A E Dovjikov et al Geology of North Vietnam (Explanation of Geological limp, scale : 500.000) Publishing House of Sciences and Technology, Hanoi 1971 (ill Vietnamese) Elies et Wood British Graptolites Paleontoligical Society, London, 1901-1918 J Giraud Notes geologique sur la partie N orth - Est du Tonkin Bull Serv Geol Indo-chine Voi V, fase 1(1918) pp 65 Nguyen Van Hoanh Newly discovered graptolite fossils in Muong Xen area and the age of Song C a Form ation, Journal of Geology, No 142(1979), pp 21-23, (in Vietnamese) c Jones G raptolites of the M onograptus hercynicus Type recorded from Malaya Nature, London Vol 215(1967), pp 497 c Jones T he SiluroD evonian graptolite faunas of the Malay Peninsula Insti tute of Geological Sciences Overseas Geology and Mineral Resources, London No 44(1973), pp 1-28 T Kobayashi H Igo Oil the occurrence of graptolites shales in north Thailand, Geol and Palaeontol Southeast Asia., Tokyo, Univ Press, Vol 2(1966), pp 1-8 10 T Koren, D Kaljo Silurian G raptolite Zones In: Graptolites and Stratigraphy, Tallin, 1976, pp 64-84 (in Russian) 11 Pham Dinh Long Lower Paleozoic sediments in the Tuyen Q uang region, Journal of Geology Hanoi No 91-92(1970), pp 14-19 (in Vietnamese) 12 Nguyen Huy Mac, P ham T he Hien Some geological problems of the Geology Co To Island and their vicinity in the Bac Bo Gulf Journal of Biology and Earth Sciences, Hanoi Vol X, No 1-4(1972), pp 37-42 (in Vietnamese) 13 E Patte E tudes geologique dans l'E st (iu Tonkin Bull Serv Geol Indochina Vol.15 fase 1, pp 314 14 Nguyen Van Phuc G raptolites ill the N orth Vietnam In: Characteristic Fossils in the North Vietnam Publishing House Sciences and Technology, Hanoi 1980 pp 57-65 (in V ietnam ese) 15 Nguyen Van Phuc G raptolite fauna in Vietnam, Proc IV- th Reg Conf Geol SE Asia, Manila, Phillipines, 1981 pp 347-354 16 Nguyen Van Phuc G raptolites in the South Vietnam In: Characteristic Fossils in the South Vietnam Publishing House Sciences and Technology, Hanoi, 1984, pp 33-38 (in Vietnam ese) 17 Nguyen Van Phuc R ecent discovery of graptolites in Binh Tri Thien Province, Proc 2-th Geol Conf o f V ietnam , Hanoi Vol 2(1985), pp 22-26 (in Vietnamese) 50 N g u y e n V an P h u c 18 Nguyen Van Phuc Silurian sediments along the Road No9 from Dong Ha to Tan Lam, Journal of Geology, Hanoi, serie A, No 208-209(1992), pp 5-9 (in Viet namese) 19 Nguyen Van Phuc Lower Devonian graptolites from the Muong Xen area (North west part of Central V ietnam ), Journal of Geology, Hanoi, series B, No 11-12(1998) pp 29-40 20 Nguyen Van Phuc The Biozonation of Silurian G raptolites in Vietnam, Journal of Geology, Hanoi, series A, Special issue, 2000, pp 10-18 (in Vietnamese) 21 D Skevington British Ordovician graptolite zones and interregional correlation In: Graptolites and Stratigraphy, Tallin, 1976, pp 171-178 22 Tran Van Tri et al Geology of North Vietnam (Explanation of Geological map scale 1:1.000.000) Publishing House Sciences and Technology, Hanoi, 1977, pp 347 23 Zhang Yuan-dong G raptolite Composite Standard Sequence (GCSS) In: Chen Xu and Bergstrom S.M Nanjing University Press, No 5, pp 67-74 T A P CHÍ k h o a học D H Q G H N , K H T N &Í C N , t.X V III, n ° l - 0 CÁC LÓP ĐÁ TRAM TÍCH CHỨA BÚT THẠCH TUOI ORDOVIC - SILUR VÀ DEVON SỚM Ở VIỆT NAM Nguyễn Vãn Phúc Khoa Địa chất, Trường Đại học KH T ự nhiên- ĐHQG Hà Nội Các lớp đá chứa bút thạch phát 26 mặt cắt phân bố từ Đại Lộc tỉnh Qung Nam - Đà Nẵng đến Tấn Mài tỉnh Qung Ninh Trong trầm tích Ordovic xác lập tầng đới chứa bút thạch (từ lèn trên): tầng chứa D flahelliform e (bậc Tremađoc), Did ahnorm is, đới u austrodentatus (bậc Arenic), tầng chứa Die gurleyi (bậc Carađoc), đới Dip bohemicus, G persculptus (bậc Ashgili) Trong trầm tích Silur có mặt 14 đới tầng chứa bút thạch (từ lên trên): đới Par acuminatus, Cys vesiculosus (=At atavus), Cor cyphus (bậc Rhuđani, Llanđovery), Dem trianguỉatus- Cor gregarius), Dem convolutus, M sedgwickii (bậc Aeroni, Llandovery), Sp turriculatus-Str exiguus, Mon griestoniensis- Mon crenulata Sp spiralis (bậc Tẻlychi, Llandovery), Cyr centrifugus- Cyr m urchisoni, tầng chứa M ct priodon (bậc Sheivuđi, Venlock), đới Pris vulgaris (bậc Homeri, Venlock) B bohemicus-S chimaera, tầng chứa M cf uncinatus ( bậc Gorsti, Luđlov), đới M form osus ( bậc Luđforđi, Luđlov), M lochkovensìs (Priđoli) Các trầm tích Đevon gồm có (từ lên trên): đới bút thạch: M uniformis, M hercynicus (bậc Lochkov), M yukonensis (bậc Praga) ... mentioned Ordovician - Silurian and Lower Devonian graptolité se quence is more complete* in all studied areas of Central and N orthern Vietnam, it is espected th at the Ordovician - Silurian and Lower. .. areas, and will be a correlation itandard ill Vietnam , where the Ordovician - Silurian and Lower Devonian are mainly ỉeveloped graptolite bearing facies We hope th a t in the near future the Vietnamese... asi 0) o C h in a D flabelliforme beds • C onjectural Zones Fig Comparison and correlation of Ordovician- Silurian- Lower Devonian graptolite zones and b of Vietnam and other countries in the vicinity.Cited