27(1),65-71 Tap chf CAC KHOA HOC VE TRAI DAT 3-2005

TAI LI$U M6I vE MAT CAT CHUAN CUACAC HE "'' / ? •

TANG SI KA, BAC BUN, MIALE TUOI DEVON S6M VONG ·DONG VAN, HA GIANG

I. DAT VAN D:E M~t cat chuan (stratotyp) cua cac h~ tang Si

Ka, Bac Bun, Mia Le Ia m~it cat LUng C6 - Ma Le, nim a phan Mt ct,rc bac cua Vi~t Nam. Can luu y, Ma Le Ia ten m¢t ban nguoi H'Mong, trong cong trinh bAng tie'ng Phap cua J. Deprat [1] ten .ban nay duqc vie't Ia "Mie-le", sau duqc chuyen ngfr tra l~i tie'ng Vi~t trong nhieu cong trinh ve dja chat khu VIJC va dja tang thanh "Mia Le", nay da thanh ten quen dung. M~t cat tren duqc J. Deprat [ 1] mo tii chi tie~ tan dau tien. Ong chia ra trong d6 cac "serie""' Lung C6, Si Ka, Bac Bun, Mia Le va Ma Pi Len (serie de Loung-co, serie de Si-ka, serie de Bac-boun, serie de Mie-le, serie de Ma-Pi-leun), trong s6 d6 4 "serie" dau duqc coi c6 tu6i Ordovic, con "serie" cu6i cung - Gothland (tuang frng v6'i Silur theo quan ni~m hi~n nay). Gan 90 nam da troi qua ke tu khi J. Deprat lam cong vi~c "khai san pha th~ch" ay, thiet nghi cling can nghien cfru l~i m~t cat d!a chat quan tn:mg nay nhim b6 sung nhfrng ke't qua nghien cfru mai nha't va c6 nh~n thfrc day du han ve m~t dt chuan cua cac h~ tang tu6i Devon sam rat ph6 bien a Dong Bac Bac Bo k€ tren. ·

Nhfrng nghien cfru gan day cua chung toi kh£ng djnh SIJ chfnh XaC Ve tr~t tiJ dja tang trong rna ta cua J. Deprat [1] . Trong khoang vai th~p nien qua, cac "serie" Lung C6, Si Ka, Bac Bun, Mia Le cling da duqc cac nha nghien cfru dja tang khu vt,rc chuyen thanh cac "di~p", va sau khi "Quy ph<;tm dja Uing Vi~t Nam" [l7] duqc ban hanh-

* Khai ni~m "serie" cua J. Deprat khong tuang frng cap "lo<;tt" hi~n dung trong th~ch dja tang, rna gan vai "h~ tang" han. Trong bai nay chung t6i t~m M nguyen d~ng Ia "serie"

T A HOA PHlfdNG

thanh cac h¢ tdng cung ten. Rieng phan "serie" Ma Pi Len theo quan ni~m cua J. Deprat trong mat cat k€ tren nay chung toi xe'p vao h~ tang Si Phai.· M<;>t suu t~p hoa th~ch phong phu g6m Tay cu¢n, Chan riu, Tht,rc v~t, Ca c6 va V6 n6n da duqc chung toi thu th~p. Danh sach hoa th~ch Slr dl,lng trong bai bao nay do cac nha c6 sinh sau day nghien cfru va xac djnh : Tay cu(m - c6 Gs Duong Xuan Hao, Ca c6 - Ph. Janvier, Chan riu - D~ng Tran Huyen, San hO b6n tia- Nguyen Due Khoa, Thuc vat c6 : Cai Chong-yang, V6 n6n - T~ Hoa Phua~g. Tac gia xin Chan thanh cam O'n CaC nha khoa hQC da hqp tac nghien cfru. Tran trQng cam an Gs T6ng Duy Thanh (DHQG Ha N¢i) va Ks Le Van Giang (Lien doan Ban d6 Dja chat Mien Bac) da t~o dieu ki~n cho tac gia di th1Jc dja thu th~p mau nghien cfru.

II. MOTA MAT CAT

M~t dt Lung C6 - Ma Le ch~y dQc theo duang 5to ttr Lung C6 ve Ma Le, thu<;>c huy~n Dong Van, tlnh Ha Giang (hinh 1 ). Chung toi khiio sat do~n tu Ta Kao (dja danh tren ban d6, frng vai ban Si Min Ka hi~n nay) tai ban Ma Le. Chung t5i chia toan b¢ m~t cat thanh 10 t~p . Trinh tt,r dja tang tl.r duai ten nhu sau (s6 thfr tt,r cac t~p danh rieng cho tung h~ tang):

H~ tang Si Ka :

l. Duai cung Ia m¢t lap s~n ke't voi day khoang . 5- 15 em phil bat chlnh hqp tren be ml;it bao mon 16i 15m cua da voi tai ke't tinh mau xam h6ng duqc J. Deprat [1] xe'p vao "serie" LUng C6 tu6i Ordovic s(:lm (hinh 2A). Thanh phan s~n Ia da v6i cua Uing da nim duai, xi mang gan ket Ia set v6i. Tren lap S<:J.O kit Ia da phie'n set v6i mau tim g~,J, xam II,IC, xen m¢t s6 10p cat- b¢t ke't cung mau. T~p day 175 m. ·

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Hinh 1. Sa do vj tri m~t cat Lung Co - Ma Le

2. Da b<:>t ket xen voi phi en set, phi en set v6i mau

xanh, xanh l~;~c, chua h6a th1,1ch Chan riu , Chan b~;~ng ,

V6 cfrng,Giap xac (Crustacea), tht,rc v~t: Taeniocrada (?) sp. va ca c6 : Yunnanolepis sp., Yunnanolepidoiei gen. et sp. indet. , Placodermi gen. et sp. indet., Sarcopterygii gen. et sp. indet. Day 250m.

3. M<:>t so lop da v6i xam den, xam hong, h1,1t mjn, pMn lop m6ng, d6i khi phan dai, xen lop voi b<:>t ket va da phien set mau xam, xam l~;~c , tim g~;~.

Day 175 m.

4. B¢t ket xen m<:>t s6 lop da phien set v6i mau xam l~;~c , tim g~;~. Day 225 m.

H~ tang Bac Bun :

1. Da phien set, phien set v6i mau xam, khi phongh6ac6 mau nau xam hong. Day 130m. Trong da phien set voi chua phong phu h6a th1,1ch tht,rc v~t. m<:>t s6 manh Giap xac, Tay cu<:>n : Howittia wangi (Hou) , Ca c6 : Yunnanolepis sp., Chan riu : Gonio­phora sp.

2. Da bQt ket mau xam, khi phong h6a c6 mau nau vang , day 100m. Trong da chua h6a th1,1ch Ca c6 Tongdzuylepis vietnamensis Janvier et Ta­Phuong (hlnh 2B), Petalichthyida gen . et sp. indet. , Minicrania sp., Ptyctodontida ? gen. et sp. indet.,

Brachythoraci ? n.g. et n. sp.

3. Da phie'n set xam l~;~c, khi phong h6a c6 mau s~c so (do, ving, hong, I~;~c , tdng). Day 70 m.

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H~ tang Mia Le :

1. B<:>t ket mau xam l~;~c xen da phie'n set va set v6i, chua h6a th1,1ch Tay cu<;>n : Euryspirifer tonkinensis (Mans.) va E .. aff. parasensis (Mans.). Day 50m.

2. Da phien set xen lap voi da phien set v6i, phan tren cling c6 m<:>t vai lap da v6i set m6ng. Day 450 m. T~p nay chua mQt t~p hqp h6a th~ch phong phu gom Tay cu<;>n :Euryspirifer tonkinensis (Mans.), Dicoelostrophia annamitica (Mans.), Atrypa aff. reticularis Lin., Elymospirifer kwangsiensis (Hou), Howellella crispa His., Schellwienella cf. douvillei (Mans.), S.lantenoisi Mans.,? Athyris tiaomachiensis Tien, Parachonetes zeili (Mans.), Undispirifer aff. pseudoaculiatus Rzons., Hysterolites sp. San hO bon tia : Hardophyllum ? brancai (Frech) ; D<;>ng v~t

hinh reu : F enestella sp. ; ca c6 : Galeaspida gen. et sp. indet. , Placodermi gen. et sp. indet. ; Giap xac : ? Phyllocarida ; BQ ba thuy : Proetus sp. va Chan riu : Pterinea mieleensis Mans.

H~ tang Si Phai :

1. Da v6i mau den h1,1t mjn xen da v6i set mau den, silic va da phien silic mau den va nau xam. Be day 110 m. Trong da voi va voi set g~p cac hoa th~ch V6 n6n Nowakia aff. zlichovensis Boucek, N. praecursor Boucek, N. barrandei Boucek et Praritl va Homoctenus sp ..

nr. cAcHE TANG TUOI DEVON TRONG MAT CAT LONG co-MALE

De phan bi¢t cac h¢ ting Si Ka, Bic Bun, Mia Le trong m~t cat chuan k€ tren, chung t6i chu yeu dl_l'a vao st,r phan chia rna J. Deprat [1] da tien hanh doi voi cac "serie" cling ten (hinh 3) .

1. H? tii'ng Si Ka (D 1sk)

H~ tang Si Ka c6 n<:>i dung va kh6i lm;mg frng voi "serie" Si Ka do J. Deprat [1] xac l~p 6 vung Dong Van, Ha Giang. Ong da m6 ta kha chi tiet m~t cat Lung Co - Ma Le, trong d6 10 t~p thuQc ve "serie" Si Ka gom chu yeu da phien set voi mau s~c s6" (do, tim g~;~, xanh l~;~c, vang), mQt so lOp da vOi mau xam hong tuong tl_l' nhu da vOi cua "serie" Lung C6 n~m duoi va mt)t s6 lap cat ket mica. Trong t~p thu 8 (da phien chua v6i mau s~c so, day 10m) 6ng da phat hi~n nhfrng phie'n cfrng cua ca Ostracodermi (Asterolepis sp., Homosteus sp.), nhfrng manh Vl;lrl tht,rc v~t (Bytrotrephis antiquata

Hinh 2. A- Ranh gi6'i bit chlnh hqp gifra cac h~ Uing Lung Co (01lc) va Si Ka (D1sk) t:;ti Ta Kao (anh T:;t Hoa Phuong); B- M¢t phan khien dau hoa th~ch ca, Ioai Tongdzuylepis vietnamensis duoc phat hi¢n

trong h¢ tang Bac Bun (D1bb) (miu LS-6, anh Philippe Janvier)

Hall) va da xe'p "serie" Si Ka vao Ordovic trung va day Ordovic thtrQllg (02-3).

D6i sanh v6'i m6 ta cua Deprat [ 1], trong phan m6 ta l:;ti m~t ciit Lung C6 - Ma Le a m11c II, h¢ tling Si Ka ung v6'i 4 tAp dliu, nim tren be m~t bat ch'inh hqp v6'i h~ tling Lung Co t:;ti vi tri ban Ta Kao. Da a tren va du6'i be m~t kh6ng phiing cua bat ch!nh hqp c6 the' nim kh6ng d6i. Be day cua h¢ tang trong m~t dt chuan khoang 800 m.

Nha c6 ngu h9c nguai Phap Ph. Janvier [13] da ra xet l:;ti cac h6a th:;tch ca rna J. Deprat [1] tim thay trong "serie" Si Ka : Homosteus sp. va Asterolepis sp .. Theo 6ng d:;tng dau tht!C ra Ia m¢t manh khien dliu cua ca Khien hinh giay (Galeaspida), d:;tng sau -m¢t so manh cua Yunnanolepiforme thu¢c nh6m ca H~u m6n d6i (Antiarchi). Ngoai ra con c6 Chuchi­nolepis (?) sp. Nhfrng miu hoa th:;tch ca .c6 rna chong t6i thu thl).p l:;ti duqc g6m : Yunnanolepis sp., Yunnanolepidoiei gen. et sp. indet. , Placodermi gen. et sp. indet., Sarcopterygii gen. et sp. indet.

Trong m~t dt chuan, m(>t hqp phan da cua h¢ tang c6 mau tim g11 d~c trung (J. Deprat [1] g9i Ia mau ba ruqu vang ho~c mau socola), xen ke v6'i cac hqp phlin khac c6 mau xam, xam Juc, hong, s~c sa. L6t day h¢ tang a m~t cat chuan Ia m(>t lop S(;ll1 ke't v6i m6ng.

T6ng Duy Thanh [ 11] ll).p tang Si Ka d€ hqp nhat cac tram tich thu¢c phan thap nhat cua Devon ha a Bac B¢. Ong coi tang Si Ka c6 tu6i Lochkov sam (0 111) . ve sau ke't lu~n nay cung duqc khiing djnh trong cac c6ng trinh c6 tinh chat t6ng hqp v€ h~ Devon a Vi¢t Nam [12, 14, 15].

2. H~ ta'ng Rife Bun (D1bb)

H¢ tang c6 n(>i dung va kh6i ltrQ'ng frng v6'i "serie" Bac Bun do J. Deprat [1] xac lAp. H¢ tang c;hie'm m(>t phan m~t dt Lung C6 - Ma Le, do~n qua deo Si Ka va ban cling ten, nim ch'inh hqp gifra cac h¢ tling Si Ka va Mia Le. Thea m6 ta cua J. Deprat, "serie" Bac Bun c6 3 t~p , chu ye'u g6m da cat ke't, da phie'n set, da phie'n v6i mau s~c so 19 a deo Si Ka, ben tren Ia m(>t tl).p day da phie'n set, cat ke't mica, cat b¢t ke't mau do, vang ho~c ph6't 1\lC, chfra h6a th:;tch Goniophora sp. va nhfrng phie'n cfrng cua ca Ostracodermi bj gi~p vo. "Serie" Bac Bun day khoang 500 m, duqc J. Deprat xe'p vao Ordovic thuqng.

Khi do ve l:;ti m~t cat Lung C6 - Ma Le, chong t6i coi 3 tAp tie'p thea, chuyen tie'p tren h¢ tang Si Ka, Ia thu¢c v€ h¢ tang Bac Bun. B€ day cua h¢ tang t:;ti m~t cat Ia 300 m. Un dau tien trong chinh m~t dt chuan cua h¢ tang Bac Bun chong t6i da phat hi¢n loai hoa th:;tch Tay cu(>n Howittia wangi (Hou) (= Hysterolites wangi (Hou), =H. wangiformis Zuong) - Ioai tieu bieu cua phfrc h¢ h6a th:;tch cling ten , d~c trung cho tang Bac Bun ph6 bie'n a Bac B¢. Ngoai ra, trong SU'U tl).p cua chong t6i con c6 cac h6a th:;tch tht!C v~t, m(>t s6 manh Giap xac, ChAn riu : Goniophora sp., Ca c6 : Tongdzuylepis vietnamensis Janvier et Ta-Phuong, Petalichthyida gen. et sp. indet., Minicrania sp., Ptyctodontida ? gen. et sp. indet. , Brachythoraci ? n.g. et n.sp.

T6ng Duy Thanh [11] I~p tang Bac Bun de lien h~ hqp nhat cac tram tich ttr6'ng bien ( c6 the xen

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68

tu<mg Vl;Jng - vjnh o doi noi) chua phfrc h~ h6a th~ch Howittia wangi. M~t d.t chuan cua tilng cling 1a mi,it cat chuan cua h~ tAng Bac Bun da mo ta o tren. Phfrc h~ h6a th~ch Howittia wangi duqc T6ng Duy Thanh [11, 12] chfrng minh c6 tu6i Lochkov­Praga (D11-p) ho~c Lochkov mu<;>n (D11z), tuong frng voi tftng Nahkaoling 6 Nam Trung Qu6c.

Khi tie'n hanh do ve ban do dja chAt ta Bao 4c (1: 200.000), Hoang Xuan Tinh va nnk [18] da g<)p cac "serie" Bac Bun va ''serie" Si Ka cua J. Deprat [1] thanh "di~p Bac Bun". Vi~c lam nay kh6ng phu hqp nhfrng nguyen tac thong thuong trong cong tac dja tAng. CAn Juu y, cling trong cong trinh ke' tren, Hoang Xuan Tinh neu khong chinh xac vj tri m~t cat chuan cua "di~p Bac Bun" theo quan ni~m cua ong : "M(it c&t duqc quan sat thea duang man tu bdn Si Ka di bdn Mia U" . Dieu nay kh6ng dung voi m6 ta g6c cua J. Deprat (1915), cling khong dung voi tht,rc te' quan sat duqc hi~n nay. Trong do~n m~t cat d6 chi!¢ m<)t phftn "serie" Bac Bun va hoan toan khong 1¢ "serie" Si Ka. M¢t dieu nfra can 1uu y : trong to ban do dja chAt Yen Minh (1:100.000), cua J. Deprat (1914) c6 Sl! nhAm IAn (dao l<)n) ve di~n phan b6 gifra hai "serie" Si Kava Bac Bun (so voi phAn mo ta) . Dieu nay da duqc ghi nh~n trong .cong trinh cua E. Saurin [9] va m¢t s6 cong trinh khac.

3. H? tiing Mia Le (D1 ml)

H~ tAng c6 n¢i dung va kh6i luqng Crng voi "serie" Mia U do J. Deprat [1] xac J~p. TrAm tich thu¢c h~ tAng chie'm phan cao trong mi,it cat Lung C6 - Ma Le, tren do<;tn du<'>'ng tu ban Si Ka tai ban Ma Le. Theo mo ta cua J. Deprat, "serie" Mia U gom hai tap : t~p duoi gom da phie'n va cat ke't mica, day 250 m, kh6ng chua h6a th~ch ; t~p tren Ia da phie'n set mftu do, vang, rat mem, dfty 250 m, chua phong phu h6a th~ch Tay cu¢n : Spirifer tonkinensis Mans. (= Euryspirifer tonkinensis), Dinorthis m;namitica Mans. (= Dicoelostrophia annamitica), Spirifer dongvanensis Mans., Strophomena sp., B9 ba thuy : Proetus sp., Chan riu : Pterinaea mieleensis Mans. va D¢ng v~t hinh reu : Fenestella sp .. Trong phan giai thich hinh ve 61 cua cong trinh ke' tren, J. Deprat da coi phan tha'p "serie" Mia U gom m<;>t t~p da phie'n mica mau vang, chuye'n tie'p len t~p da set voi mau hong chua Spirifer tonkinensis Mans. va Dinorthis annamitica Mans. ; phAn cao cua "serie" .Mia U gom t~p da phie'n set voi va set voi . Trong t~p nay

c6 xen d. cat ke't va m<)t lap da voi set. "serie" Mia Le nam chinh hqp tren "serie" Bac Bun (Deprat viet nhim Ia tren "serie de Si-ka") va chuyen tiep len "serie" Ma Pi Len, duqc xep vao Ordovic thuqng - Gothland h~ (hinh 4).

Khi do ve l<;ti chi tie't m~i.t cat Lung C6 - Mia Le, chung toi coi 2 t~p tiep theo, chuyen tiep tren h~ tAng Bac bun, Ia thu¢c ve h~ tAng Mia U. Trong h~ tAng gomchu yeu Ia cat b¢t ket, da phien set va

Hinh 4 . Do<;tn m~t d.t qua h~ tang Mia Le t~i m~tcat chuan (theo

hinh 61 trong Deprat, 1915)

"Serie "Bile Bun : 1 - da phie'n set, cat ke't h<;tt th6. "Serie" Mia U phdn thcip :

250 2 - da phie'n mica, set voi, 3 - set voi mau hong chfra Euryspirifer tonkinensis,

Dieoelostrophia annamitiea. "Serie" Mia U phdn eao : 4- phie'n set voi, va set vOi, cat kit, voi set (!lap). "Serie" Ma Pi Len(= H¢ td'ng Si Phai) : da voi chua silic

set vOi nay chung tOi da thu th~p them duqc cac hoa th~ch sau : Euryspirifer tonkinensis (Mans.), E. aff. parasensis (Mans.). Dieoelostrophia annamitiea (Mans.), Atrypa aff. retieularis Lin., Elymospirifer kwangsiensis (Hou), Howellella erispa His., Sehell­wienella cf. douvillei (Mans.), S. lantenoisi Mans., ? Athyris tiaomaehiensis Tien, Paraehonetes zeili (Mans.), Undispirifer aff. pseudoaeuliatus Rzons., Hysterolites sp. San ho b6n tia : Hardophyllum ? braneai (Frech), D<)ng v~t hinh reu : Fenestella sp., Giap xac : ? Phyllocarida, BQ ba thuy : Proetus sp., Chan riu : Pterinea rnieleensis Mans. ca c6 : Galea­spida gen. et sp. indet. , Placodermi gen. et sp. indet. Day cung Ia nhiing di tich ca c6 dau tien dugc phat hi~n trong h~ tang Mia Lea B<k 8¢.

T~p hgp h6a th<;tch phong phu tren thu<)c phfrc h~ Euryspirifer tonkinensis d~c trung cho tang Mia Le, dugc T6ng Duy Thanh [10-12, 14, 16] chfrng minh c6 tu6i Praga (DJp).

4. Hf tang Si Phai (D1•2 sp)

T<:ti phan tren cling cua m~t cat Lung C6 - Ma Le !<) ra ph an thap nhat cua h~ tAng Si Phai *, nam

* Ve ten g9i cua phan vj th<:tch dja tang nay t~i cac m~t dt Devon vling Dong Van - Yen Minh hi~n chua c6 S\I th6ng nhat trong cac van li~u dja chat. H~ tang da voi xem silic chu yeu c6 tuang nuac sau nay tung dugc mo tii duai cac ten Na Quiin, Si Phai va Ban Pap. Trong bii bao nay, chung toi t<;tm M ten h~ tang Si Phai cho th6ng nhat vai cong b6 gan day cua chung toi [7, 8].

chuyen tiep lien t1,1c len h~ tAng Mia u, gom chu yeu Ia da voi, da voi set, voi silic va da phien silic mftu xam den (frng vai phftn thap cua "serie" Ma Pi Len, theo J. Deprat 1915). Be day cua h~ tang trong mi;i.t cat nay khoang 50 m. Trong da voi cua h~ tang Si Phai, chung t6i da gia cong va xac djnh dugc cac hoa th<:tch Yo non thu<)c cac dai ttr zliehovensis de'n barandei : Nowakia aff. zliehovensis Boucek, N. paeeursor Boucek, N. barrandei Boucek et Prantl va Hornoetenus sp .. Cac doi hoa th~ch Yo n6n k€ tren thu¢c ve b~c Emsi (D 1em) cung da dugc phat hi~n trong phan thap h~ tang Si Phai t<;ti m~l.t cat Dong Van - song Nho Que' va cac vling Ian c~n cua Ha Giang [2, 4-8].

M(>T v AI NH~N XET v A KET LU~N

Vi~c nghien cfru l~i cho phep nhin nh~n day du han ve m~t dt chuan cua cac h~ tang Si Ka, B<ic Bun, Mia U , d~c bi~t Ia thu th~p them dugc nhieu tai li~u c6 sinh va nh~n bie't dugc m6i quan h~ giii'a cac h~ tang.

Un dau tien hoa th<;tch Tay cu<)n Howittia wangi duqc phat hi~n trong m~t cat chu'an cua h~ tang Bik Bun. Day chinh Ia loai tieu bieu cho phfrc h¢ hoa th~ch cling ten, d~c trung cho td'ng Bile Bun a Dong B<ic B<ic B<) . Cung Ian dau tien trong h~ tang Mia Le da phat hi~n duqc cac di tich Ca c6 thu<)c cac lap Khien hinh gifty (Galeaspida) va Da phie'n (Placodermi).

Ye h~ tang Si Ka, c6 th€ n6i nha m<)t hqp phan da c6 mau tim g1,1 (c6 the Ia mau thfr sinh?) rna c6

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the phan bi~t duqc n6 tuong d6i de dang d6i voi cac h~ tang Lung Co ncim duoi va Bac Bun nim tren. M(>t s6 lop da v6i mau xam den, xam hong, h~t mjn (gan giong voi da voi cua h~ tang Lung

Co) g~p t~i phan gifra cua h~ tang cling Ia d~c diem dang luu y, vi kh6ng phai a m9i noi phan bo cua

h? tang cteu g~p cac lap da voi nay.

H~ tang Mia I.i: nci~ chlnh hqp tren h~ tang Bile Bun va chuyen dan len h~ tang Si Phai. C6 dieu dn luu y, 6 m~t cat chuin Lung C6- Ma I.i:, cilng nhu 6 m~t cat Dong Van - Song Nho Que' gan d6 [7], dt. kh6 phan bi~t r:;tch roi hai h~ tang Bac Bun va Mia I.i: ne'u chi can cfr vao thanh phan tram tich. Chung toi t~m -chap nh~n mQt each tuong doi : tang da chua nhfrng di tich Euryspirifer tonkinensis dau tien, ho~c nhfrng dang thuang di voi n6 trong phfrc h~ h6a thach cung ten (nhu Dicoelostrophia annamitica ... ) Ia day cua h~ tang Mia I.i:. Chung toi hieu, khi v~n d1,1ng each · ph an chi a theo thang th~ch dja tang vao tht,rc te' khong phai bao gia cilng thuan lqi, nhat Ia khi chuyen cac phan vj dja tang da duqc xac J:l.p tu truoc sang h~ng hinh lo:;ti th:;tch dja tang .. Do vay, vi~c xac l~p cac phlin vj cap lot;zt bao g6m m<}t so h¢ tdng tu6i Devon sam c6 le cling Ia dieu dn xem xet.

Bai b~o duqc hoan thanh voi st,r h6 trq kinh phi cua Chuong trinh Nghien cfru Khoa h9c Co ban (tf9i d6ng Khoa h9c Tt,r nhien, B<} Khoa h9c va Cong ngh~).

TAl LIIJ;U THAM KHAO

(1,l J. DEPRAT, 1915 : Etudes geologiques sur Ia region septentrional du HautTonkin (feuilles geolo­giques de Pakha, Hagiang, Mapilo et Yenminh au IOO.OOOe). Mem. Serv. Geol. lndoch., Vol. IV, fasc. 4 . Hanoi .

[2] D,A.NG TRAN HlJYEN, 1976: Phat hi~n Tenta­culites Devon vung D6ng Van va y nghia dja tang cua chung. Ts Sinh va~- £?ja h9c, XIV, 2, 61-63.

[3] PH. JANVIER & TA HOA PHUONG 1999 : Les Vertebres (Placodermi, Galeaspida) du Devonien inferieur de Ia coupe de Lung Co - Mia I.i:, province de Ha Giang, Viet Nam, avec des donnees complementaires sur les gisements a vertebres du · Devonien du Bac Bo Oriental. Geodiversitas , 21 , 1, 33-67.

[4] F. PARIS,TA HOA PHUONG, V. BAUDU, 1993 :

Decouverte d: chitinozoaires et de scolecodontes

70

dans l'Emsien du Vietnam (coupe de Dong Van -Nho Que, Province de Ha Giang). N. Jb. Geol. Palae­ont. Mh., H10, Stuttgart (CHLB Due): 596-606.

[5] TA HOA PHUONG, 1994: New discovery of Devonian and Lower Carboniferous pelagic fossils in Dong Van area (Ha Giang province, VietNam). Proc. of the Intern. Symp. on Strat. Correl. of Southest Asia, Bangkok: 62-68.

[6] T,A. HOA PHUONG, LE VAN GIANG, 1996: Tai li~u moi ve dja tang Devon h:;t vung Yen Minh - Ml).u Du~, Ha giang. Tc Dja chat, 237, 6-13.

[7] T,A. HOA PHUONG, 2000: Dja tang Devon, Carbon trong m~t cat D6ng Van (Ha Giang). T1;tp

chi Dja chat, lo1;tt A , Ph1,1 truong/2000, 2-9.

[8] TA HOA PHUONG, 2002 : Devonian and Carboniferous conodont biostratigraphy of the Dong Van Section, Ha Giang Province. Journal of Geology, series B, 19-20, 14-2.

[9] E. SAURIN, 1956 : Lexique stratigraphique international. Asie. 6a. lndochine. 140 pgs. Paris.

[10] TONG DUY THANH, 1976 : Tu6i cua "tang

Mia I.i:" a Dong Bac Vi~t Nam. Sinh v~t- Dja h9c. XIV, 4, 97-104.

[ 11] TONG DUY THANH, 1979 : Dja tang Devon h~ 6 khu vt,rc Bac B9. Tc CKHvTD. T. 1, 1, 2-8.

[12] TONG DUY THANH va nnk, 1986 : H~ Devon 6 Vi~t Nam. Nxb Khoa hQc va Ky Thu~t : 141 tr. Ha N(li.

[13] TONG-DZUY THANH, P. JANVIER, 1987 Les Vertebres devoniens du Vietnam. Annales Paleont. V. 73,165-194. Paris.

[14] TONG DUYTHANH va nnk, 1988: Dja tang va hoa th:;tch Ru¢t Khoang Devon cua Vi~t Nam. I. Dja tang: 184pgs. Nauka. Novosibirsk (Nga van).

[15] TONG-DZUYTHANH, 1993: Mll.jor features

of Devonian stratigraphy in Viet Nam with remarks on Palaeobiogeography. Geology (Geoi.Surv. Viet Nam). B. 1-2,3-18.

[16) TONG-DZuY THANH, TA HOA PHUONG, 1994 : New Data for Correlation of Early Devonian Bearing the Euryspirifer tinkinensis fauna in Vietnam ·and South China. Subcom. on

Devonian Stratigraphy - Newsletter, 11, 69-69.

[17] TONG DUY THANH, vo KHOc. PHAN cv TIEN, 1994 : Quy ph <;~.m dja uing Vi~t Nam. O.;~c Dja chit Vi~t Nam. Ha N¢i. 76 trang.

[18] HOANG xuAN TiNH,l976 : Ve cac tram tich Devon dt.roi 6 to Bao ~c. Tin BDDC, 30, H.3. N¢i.

SUMMARY

New data on the stratotypes of Early Devonian Si Ka, Bac Bun and Mia Le formations, Dong Van district,

Ha Giang province

The Lung Co - Ma Le setion containing the stra­totypes of 3 formations (Si Ka, Bac Bun and Mia Le Formations) was described firsly about 90 years ago.

In this article the author gives supplementarily -pale­ontological data Which were collected and studied recently. These fossils are the representatives of fol­lowing groups : Brachiopods, Bivalves, Plants, Fishes, Tetracorals and Tentaculites. The existence of these fossils allows to confirm the position of ab'ove-men­tioned formations in the chronostratigraphical scale.

Due to the new materials and observation, we have a complete knowledge about the stratotypes of three Early Devonian formations which are largely distributed in the North-East of Sac Bo (such Si Ka, Sac Bun and Mia Le formations) and the regional stratigraphical correlation becomes more favourable.

Ngay nh¢n bai · 6-10-2003 Tru&ng Dgi hr;c Khoa hr;c Tif nhien Ha N(Ji

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