2007b on some new significant unconformities pleozoic and mesozoic stratigraphy of north viet nam

ĐẠ I HỌ CQUỐ CGIAHÀNỘ I VIETNAM NATIONAL UNIVERSITY, HANOI I SSN Ũ 6 ■ KHO JO U RN AL DF SCI EN CE CÁC KHOA HỌ CTRÁI ĐẤ T EARTH SCIENCES V o lu m e 23, N o 3, 2007 VIETNAM NATIONAL UNIVERSITY, HANOI i -O C O JÔ C GIA HÀ NỘ I TẠ P CHÍ KHOA HỌ C JOURNAL OF SCIENCE E d ito r-in -C h ief: Prof Dr.Sc Nguyen Hoang Luong D ep u ty E d ito r-in -C h ief: Assoc Prof Dr.Sc Luu Van Boi E d ito rial C o u n cil Prof Dr.Sc Nguyen Hoang Luong (Chairman) Assoc Prof Dr.Sc Luu Van Boi Assoc Prof Dr.Sc Le Van Cam Prof Dr Dinh Van Due Dr.Sc Nguyen Dinh Due MA Nguyen Van Loi Prof Dr Tran Nghi Assoc Prof Dr Nguyen Nhuy E d ito rial B o ard o f E arth Scien ces Prof Dr Tran Nghi (Head of Board) Assoc Prof Dr Truong Quang Hai Assoc Prof Dr Nguyen Dinh Hoe Prof Dr Nguyen Cao Huan Assoc Prof Dr Pham Van Huan Assoc Prof Dr Phan Van Tan Dr Nguyen Van Vuong Editorial Secretary: Assoc Prof Dr Nguyen Nhuy E ditorial O ffice: 144 X uan Thuy, Cau Giay, Hanoi T e l: 84-4-7547902; Fax: 84-4-7547583 P ublication P erm it 03/G P -B V H T T Issued 03/01/2002 VNU Journal of Science, Earth Sciences 23 (2007) 137-146 On some significant unconformities in the Paleozoic and Mesozoic stratigraphy of North Viet Nam Tong D zuy Thanh’*' College o f Science, VN U Received 10 July 2007 Abstract A lot of unconformities and stratigraphic gaps have been discovered in the Paleozoic and Mesozoic stratigraphy of Bac Bo region (North Viet Nam), but their role in the regional geology was not accessed yet in detail This paper is the first attempt to describe the most significant unconformities and stratigraphic gaps and discussing their role in regional geology The most important is the angular unconformity of Norian-Rhaetian formations upon various formations of different formations; it marked the change tectonic regime of the region resulting from the indosian orogeny in Viet Nam and in Southeast Asia in common The gap of Lower Devonian red beds formations (Si Ka Formation, Song Cau Group) upon Lower Paleozoic formations (Upper Cambrian Than Sa Formation, Lower Ordovician - Lutxia and Na Mo formations) is a regional unconformity, which had been taken place in the epicaledonian terranne of South China and North East of Viet Nam The gap between the Da Mai Formation and the Dong Dang Formation was a result of a crust rising, but was not through the orogeny activity, although after this gap the structural plan was more differentiated Other unconformities and stratigraphic gaps seems to be local unconformities, for instance, the one of the Tan Lap Formation (D2g-D3 fr tl) upon the Ban Pap Formation (D)p-D3 fr bp) and the unconformity between the Sinh Vinh ( 3-S so) and the Ben Khe (E-O] bk) formations Keywords: Unconformity; Stratigraphy; Paleozoic; Mesozoic In tro d u ctio n data from d ifferent g eological dom ains, for instance facial analyses, m agm atic activities, tectonical A lot of u ncon form ities and gaps have been fram ew ork etc., the stratigraphic described in Paleozoic and M esozoic stratigraphy relations (unconform ities and gaps or hiatus) of N orth V iet N am F rom the u nconform ities play an im portan t role in dealing w ith this and gaps in com bin ation w ith the facies of question T his pap er is an attem p t to design an underlying and overlyin g form ations geologists approach can draw the first step for interp retation o f their stratigraph ic gaps, h iatuses, and unconform ities role in the geolog ical d evelopm ent o f the in the geolog ical d evelop m en t of the country region A lthough exp laination of to u nd erstan d the role o f som e the The N orian angular u nconform ity had taken geological d evelopm ent o f a region requires shape during the indosinian orogeny, and has the been w ell-know n in the g eology o f V iet N am and in Sou th east A sia H ow ever, there are a lot *Tel.: 84-4-8572246 E-mail: tongdzuy@vnn.vn of d escribed u ncon form ities and stratigraphic 137 Tong Dzuy Thanh /VNU Journal o f Science, Earth Sciences 23 (2007) 137-146 138 gaps in the geology o f the cou n try hav e not yet been assessed, althou g h they play an im portant from Lang P hoi to D a D inh villages The unconform ity o f the Song M a Form ation role in the in terp retation o f geolog ical h istory of (£2 sm ) upon the N am Co Fm (PR3-£i nc): The the territory For instance, the gap betw een unconform ity of the Song M a Form ation (£2 sm) Low er Paleozoic upon the N am C o Form ation (PR3-£i nc) can form ations in the stratigraph ie sequence of clearly b e observed in the Suoi Toi Section N orth B ac Bo (H a G iang, L ang Son, and Thai (Thanh H oa P rovince), Ban N am - Ban Thay, N guyen provinces) is a b ig stratigraphie event Ban M o sections, in the u pper course of the Ban in the region This gap togeth er w ith the large Pha Stream distribution of L ow er D evon ian red bed s is an C hau D istrict, Son La Province), in the Na obvious the H uong - Na V ien Section , and on Sam Co Pass Caledonian orogeny C ontrary to the conception (Km N o.18 - K m N o.21 on the road from M of m any geologists, in the area o f the D a River Son to Song M a) D evonian evidence and of L ow er the influence of basin (W est B ac Bo region) a gap betw een (C hieng P ac C om m une, Thuan The g ap betw een A n Phu (N P -£i hg) and Ha D evonian and its u nd erly ing form ation s is not G iang (£2 hg) form ation s: T h e first gap in Low er observed D evonian P aleozoic in the n ortheast of B ac Bo is observed form ations are ch aracterized b y the continuous in the sequence betw een the Song C hay Group H ere the Silu rian and sequence from Sinh V inh Form ation ( 3-S sv) to (An Phu Form ation) and the overlying Ha Bo H ieng (S2 bh) and Song M ua form ations (D] G iang F orm ation that o ccu rs in som e sections in sm) The stratigraphie seq u en ce proves that the Ha G iang Province Da R iver basin w as not influen ced b y the The u nconform able relation betw een the Sinh C aledonian orogeny, w hich occurred in pre- Vinh D evonian period form ation s: This paper is the first attem p t to d escribe the m ost significant u ncon form ities (O3-S sv) T his and the Ben u nco n fo rm ity Khe (£-O i bk) w ith basal conglom erate in the bottom o f the Sinh Vinh and Form ation is w ell exposed in m any localities stratigraphie gaps, and to d iscuss their role in such as Ban C ang, Sin h V inh M outh, Ban Ban, regional geology and Suoi N hap Stream (low er section of the Da River basin) The u nconform ity o f the Low er D evonian upon Paleozoic unconformities and gaps Low er P aleozoic form ation s is expressed in the stratigraphic relation o f the Si Ka Form ation (Di 2.1 N um erous u nconform ities an d gaps w ere described in the P aleozoic o f the B ac Bo region sk), Song Cau G roup (Di sc) w ith the underlying form ations such as L ow er O rdovician Lutxia of Form ation in D ong V an D istrict (Ha G iang stratigraphie Province), U p p er C am brian T h an Sa Form ation studies, a lot o f unconform ities and stratigraphie in T h an Sa area (Thai N guyen Province) and Ha gaps Thanks d ifferent to the scales geolog ical and th em atic m appin g been Lang D istrict (C ao B an g Province) T he Si Ka discovered and d escribed A m ong them , the Form ation belongs to the red continental facies, follow ing and its lithological com p osition and color have in P aleozoic of B ac u nconform ities Bo and have stratigraphie gaps can be listed: The unconform ity o f the Cam D u on g Form ation (£( cd) upon the D a D inh Fm (PR3 dd): this led m any geoscientists to correlate it w ith the "O ld Red Sand stone" lying at the base of the D evonian System stratigraphie relation can be follow ed along the The unconformity between Tan Lap (D2g-D3 fr tl) contact betw een these tw o form ations extending and Ban Pap form ation s (D tp-D fr bp) is an Tong Dzuy Thanh /VNU Journal o f Science, Earth Sciences 23 (2007) 137-146 139 interesting u nconform ity, in w hich the tongue- contact w ith the u nd erly ing Lutxia Form ation shape Tan Lap Form ation w ed ges w ithin the L ate O rd ovician in ag e (Fig 1, Fig 8) Ban Pap Form ation \ Bac Bun F (D bb) Grev chocolate shale ,~ _ S ~ S~j\ marfy shale Howittia wangi Fauna —'y y ■ ■ '/ Si Ka F (D, sk) Marly shale, black-grey silt stone Conalomerate in bottom (after Hoana / - / - / - / - \ XuanTinh etal 2000) The unconform ity o f the N am P ia Form ation (D| np) on Sink Vinh ( 3-S su) and D ong Son (Oi ds) form ations: This stratigraphic Low e r D evonian relation betw een Low er P aleozoic and L ow er D evonian Silurian is expressed in the n ortheastern side of the Song M a structu re only - in the u pper basin of \ c (0 D a R iver and in the low er basins of the M a Upper part o f the Lutxia F (0,/x) Ash ■ \ grey clay shale, siltstone and sandstone J limestone containing Hysterolenus sp and ~) other Lower Ordovician Trilobiets > ■0 River (W est B ac Bo) The unconform ity o f the T oe Tat Form ation (D3C]fr tt) upon the Lung N am ( Q Middle Ordovician - Silurian hiatus In) Form ation occurs in H a L ang area only, w here these form ations are exposed The unconform ity o f U pper P erm ian upon the Da M Form ation (C i-P dm ) has been observed Fig Unconformity between the Si Ka Formation upon the Lutxia Formation and a Middle Ordovician - Silurian gap between them (Dong Van sections, Ha Giang Province) in alm ost all sections w here these form ations By are exposed In the M esozoic stratograp hy o f Bac Bo, m any u nconform ities have been noted, bu t the lith olog ical characteristics, properties, bedding color of rock, and by fossil rem ains the Si K a F orm ation itself is a red m ost interesting is the N o rian -R h aetian upon continental form ation, and it has been compared form ations of d ifferent ages It is a regional w ith the "O ld R ed Sand ston e" lying at the base unconform ity and its im p ortant role in the of geology not only in B ac Bo, bu t also in geology extends in m any areas o f N orth Bac Bo, such as of V iet N am and o f So u th east A sia in general in D ong V an D istrict (H a G iang Province), Chi The m ost significan t u ncon form ities and the D evon ian System Its distribution Lang and Bac So n districts (Lang Son Province), stratigraphic gaps and their role in the geology Than of Bac Bo w ill be presented and d iscussed in the Province) In Ha Lang and D ong K he districts Sa, Trang Xa areas (Thai N guyen (C ao B ang Province) it occurrs as low er layer of follow ing sections the Song C au G roup, the low erm ost of w hich 2.2 U nconform ity o f the L ow er D evonian upon Cambrian and /or Ordovician form ations often begins by co n g lo m erate w ith pebble of different lithological com position and dimension In the sequence of H a Lang (Cao Bang The first regional u nconform ity has been and Province) and T h an Sa sections (Thai N guyen C am brian and / or O rd ovician form ations in the Province) O rd ovician and Silu rian sedim ents northeastern region o f Bac Bo (Ha G iang, Cao are n ot found, and the Si Ka Form ation covers Bang, Lang Son, and T hai N g u y en provinces) It in direct contact w ith the u nd erlying Than Sa is well expressed by the sequence o f the Low er Form ation of the L ate C am brian age (Fig 2, Fig D evonian Si Ka Form ation (D i sk) and the 8) underlying form ation in m any sections in D ong N guyen P rovince), not far from the T han Sa, discovered betw een L o w er D evon ian H ow ever, in the T ran g Xa area (Thai V an D istrict (H a G iang P rovince) In all these though the d irect co n tact betw een the Si Ka and areas the Silu rian sedim ents h ave not been the u nd erlying form ation is not observed, but discovered, and the Si K a Form ation w ith basal the U pp er O rd ovician Na M o Form ation and conglom erate Silu rian sedim ents are also absent So, in this is alw ays observed in direct Tong Dzuy Thanh /VNU Journal o f Science, Earth Sciences 23 (2007) 137-146 140 area, S ilu rian sed im ents n o t exist, and the Si is d ifferent from those in the north o f Bac Bo Ka Form ation can be considered as unconformable The u nd erlyin g form ations are Co To and Tan u p on the N am M o Form ation (Fig 3, Fig 8) M form ations o f O rd ovician -Silu rian age, and the overlying is M id d le-U pper D evonian D o Mia Ls Fm (D, ml) Argillaceous shale, mudstone, and marly shale containing Brachiopods, Corals of Euryspirifer tonkiner/sis Assemblage Lower Devonian Song Cau Group (D, sc) Conglomerate, sandstone, and argillaceous shale containing HowiUia wangi 0* 0' o ’ 0' o ‘ c (Brachiopod) and microvertebrate remains So n Form ation, so the gap betw een u nderlying and overlying form ations is shorter and later than the one in the north o f B ac Bo The L ow er D ev o n ian red sed im ents are very w id ely exposed in South C hina (Y u nnan Silurian and Ordovician - Silurian hiatus Ordovician G uangxi provinces) and have been d escribed as the L ian h u ash an Form ation and its Cambrian ■ / — / — Upper part of the Than Sa Fm (£, fs) Sandstone, argillaceous shale, calcareous shale containg Upper Cambrian Trilobites equivalents, w hich consist m ainly o f sandstone, m udstone, and basal conglom erate in m any cases The L ow er D evon ian red sed im ents are very w id ely exposed in South C hina (Yunnan Fig The Song Cau Group with basal conglomerate unconformable overlies the Than Sa Formation, between which there is an Ordovician-Silurian hiatus (Ha Lang sections, Cao Bang Province) -^2 Lower Devonian Bac Bun Fm (D, bb) Grey limestone, marly shale containing Corals, Brachiopods of the Howittia kvang/Assemblage Si Ka Fm (D, sk) Red sandstone, mudstone containing microvertebrate and G uangxi P rovinces) and have been described as the L ian hu ashan Form ation and its equivalents, w hich consist m ainly o f sandstone, m udstone, and basal conglom erate in m any cases The great th ickn ess (reach to m ore 1000m ) and abu ndant m icrovertebrate rem ains are the m ost rem arkable ch aracteristics o f these continental and sub continental sedim ents O bviously, this "red sand stone" w as d eposited in the tin ental and su bcontinental Silurian environ m ent after the C aled on ian orogeny Middle Ordovician - Silurian hiatus 2.3 U nconform ity betw een N am Pia and Sinh Vinh, Ordovician Upper part of the Na Mo Fm (O, nm) Ash-grey day shale, sittstone and sandstone, limestone containing Hysterofenus sp and other Lower Ordovician Trilobites D ong Son form ation s T he N am Pia F orm ation (Di np) is L o ch kovian -P ragian in age and extend s in the Fig A Middle Ordovician-Silurian hiatus between Na Mo and Si Ka formations (Trang Xa sections, Thai Nguyen Province) northeastern side o f the Song M a structure - in the u pper basin o f D a R iver and in the low er b asin s o f M a R iver (W est B ac Bo) A ccord in g to B ui Phu M y, at the N am Pia M ou th section In C hi L an g and B ac Son areas (Lang Son (upper basin o f the D a R iver), the low erm ost Province), O rd ovician and Silu rian sedim ents b ed s o f the N am Pia Form ation consists of have n o t b een found, and there is lim eston e o f puddingstone, C am brian (?) age, and the Si Ka red sand stone w hich rests u ncon form ably u p on the Sinh V inh o verlies F orm ation (O3-S sv) In the lo w er part o f the M a u nconform ably this C am brian (?) lim estone conglom erate and gritstone, R iver basin, near the H am R ong bridge area Another unconformity of Devonian sediments (vicinity o f Thanh H oa Tow n), an u nconform ity on old er form ations is observed in the east of occurrs betw een the N am Pia and the underlying B ac B o (Q uang N in h Province), bu t in this area D ong Son F orm ation (Fig 4, Fig 8), bu t it w as the age o f u nd erly ing and overlying form ations characterized as "p seudo-conform ity" Tong Dzuy Thanh /VNU Journal o f Science, Earth Sciences 23 (2007) 137-146 - , _ — — / c p © Q — / perhaps the w estern region of B ac B o w as n ot - / 1 / / Nam Pia Fm (D, np) Conglome­ rate and gritstone, coarse-grained quartzite, shale, marl, limestone interbeds and lenses containing abundant Lower Devonian corals / 141 influenced by the C aled on ian orogeny as the ea stn o rth em region, and in the low er D a R iver basin the sed im en tation did not cease during Silu rian - the tim e w hen it w as in the northeast c « 2.4 U nconform ity betw een Tan Lap and Ban Pap form ation s w Middle Ordovician - Silurian hiatus A n in terestin g u nconform ity is the one betw een the Tan Lap (D 2g -D fr tl) and the Ban Pap (D ip -D fr bp) form ations (Fig 5, Fig 8) c « o > o — — — — — — — — — — — " / _ _ / /" o _ _ _ _ The B an P ap F orm ation consists of grey bedded Dong Son Fm (Ot c/s) Siltstone, quartzitic sandstone, and marl con­ taining Lower Ordovician Trilobites, Bivalves, and Brachiopods lim eston e containing abu ndant fossils of C orals, Strom atoporoid s, Brachiopods, and others, and w id ely extend s in bo th the east and the w est of B ac B o region It is an u ninterru pted form ation, Fig Middle Ordovician-Silurian hiatus between the Lower Ordovician Dong Son Formation and the Lower Devonian Nam Pia Formation in the vicinity of Thanh Hoa Town the low erm ost bed s o f it has been dated as E m sian based on C onod onts (Pol Excavates Zone: Pandorinellina steinhornensis, Pol excavatus, Pol nothoperbonus) and D acryoconarids (N ow akia barrandei Zone), and the u pperm ost bed s is T he stratigraphic relation betw een L ow er P aleozoic form ations and L ow er D ev o n ian of Frasnian, m ay be low er Frasnian w ith Conodonts Pa transitans and som e Strom atoporoids those form ation s is interesting and is w orth noting for an analysis The The T an Lap Form ation consists m ainly of u nconform ity sand stone containing land p lant rem ains of occurrs only in the n ortheastern side o f the L ep id odendropsis, and is restrictively exposed Song M a structure, w hile in ad jacen t areas of in som e areas o f C hi L an g and B ac So n districts the lo w er section of the D a R iver, w here (Lang Son Province) It u nconform ably rests P aleozoic sedim ents are w id ely spread and w ell u p on lim estone o f the B an Pap F orm ation w ith studied, and there is no hiatus in the sequence basal conglom erate (Fig 5, Fig 8), am ong w hose from O rd ovician to L ow er D evonian pebbles are grains of igneou s rocks transported T he stratigraph ic relation b etw een Low er from a nearby erosive area w ith granite m assifs P aleozoic form ation s and L ow er D evon ian of In its turn, the Tan Lap Form ation is conform ably those form ations is interesting and is w orth covered b y E arly Frasn ian lim estone of the Ban noting for an analysis In the low er basin o f the Pap Da w id ely relations and the restrictive d istribu tion areas, spread and w ell studied, and there is no hiatus the T an Lap F orm ation is referred to a tongue- or R iver, P aleozoic u nconform ity sed im ents betw een are O rd ovician Form ation W ith these stratigraphic and shape stratigrap h ic bo d y w ed ges itself in the D ev o n ian sedim ents W hile in the n ortheastern U pp er p art o f the B an P ap Form ation This side o f the Son g M a structure the h iatus is u nconform ity and the tongue-shape Tan Lap occurrs betw een O rd ovician or Silu rian and Form ation L ow er D evonian Thus, this h iatus took place rem ains show that there w as an in terruption in only in the m arg in of an u plifting structure, bu t sed im entary process by a rising of the crust, bu t n o t in the cen ter of the sed im entary basin w as T hese unconform ity evid ences evoke a su ggestion that bearin g p artially only, Lepidodendropsis and this is p lan t a local Tong Dzuy Thanh /VNU Journal o f Science, Earth Sciences 23 (2007) 137-146 142 Lithostratigraphy Chronostratigraphy form ations of Early T riassic age is likely conform able, b u t there is a sh ort gap betw een those form ations, in fact 1 , rz i I Dong Dang Formation (P,1 dd) Chert, bauxite, and siltstone, frag­ mented cherty limeston, limestone containing Palaeofusulina In Lung Cam section - The Dong Dang overlies the eroded surface of the Da Mai limestone I I I I I I I Fig The tongue-shape Tan Lap Fm wedges within the Ban Pap Fm Tan Lap section, Lang Son Province (1: Tan Lap Fm.; 2: Ban Pap Fm.; 3: Mia Le Fm.) Wuchiapingian (Lower of Upper Permian) hiatus I I r I I I A n analogue h as been observed in the stratigraph ic sequence of M id d le-U pper D evonian o f Sou th C hina A ccord ing to the oral c,-p2 T T 1 , I I I in form ation of H ou H ong-fei, there w as M id d le D evonian coarse terrigenou s form ation, r a Da Mai Fm (C,-Pj dm) Dark grey to light grey thick bedded to massive limestone containing foraminifers from Visean (Lower Carboniferous) to Capitanian (Middle Permian) nEr sim ilar form ation o f the Tan Lap, w ed ges itself in the M id d le-U p p er D evon ian lim estone form ation 2.5 U nconform ity betw een D ong D ang and D a M form ation s The D a M Form ation in eastern B ac Bo Fig A short hiatus between Dong Dang Formation and Da Mai Fm corresponding to Wuchiapingian (Upper Permian) was noted Doan Nhat Truong's new data shown that the top of Da Mai Fm can be up to Wuchiapingian, in this case the hiatus is even shorter - between adjoining Wuchiapingian and Changhsingian stages region has b een dated as E arly C arboniferous M id d le Perm ian, w hile the low erm ost o f the A ccord ing to D oan N hat T ru o n g 's new data overlying D ong D ang Form ation is referred to in som e localities the top of D a M F orm ation U p p er b ears P erm ian u nconform able (C hanghsingian) relation betw een the The D ong the foram inifers of Codonofusiella - R eichelina A ssem blage, and h as b een dated as D ang Form ation and the u nd erlying D a M W u chiap ing ian F orm ation h as b een observed in alm ost all p resen ce o f P alaeofusulina the low erm ost o f the age (Late Perm ian) By the sections w here these form ation s are exposed D ong D an g F orm ation has b een referred to (Fig 6, Fig 8) T his u nconform able b o u n d ary is C han g h sin g ian stage o f U p p er Perm ian, thus m arked b y the change in lithology, betw een the the gap in the sequence of U p p er P erm ian in light-grey eastern B ac B o is short (betw een the tw o b lack -g rey thick-bed ded lim eston e terrigenou s-ch erty or and the black-grey carbonaceou s shale and m arl beds A ccording ad jacent W u chiap ingian and C hanghsingian tim es only) to the above m entioned data, the gap betw een Relating to this unconform ity and the bauxite D a M and the D on g D an g form ations is d ep osit in D ong D ang Form ation, D oan N hat correspond ing to the W u chiap ingian, i.e the T ru on g w rote that the bau xite ore d eposit in the first tim e o f the L ate P erm ian epoch The L ow er p art o f the D ong D ang Form ation w as stratigraph ic relation betw een D ong D ang and form ed during karstic process in the continental the en viro n m en t on the lim estone of the D a M overlying H ong N gai and Lang Son Tong Dzuỵ Thanh /VNU Journal o f Science, Earth Sciences 23 (2007) 137-146 143 The V an Lang Form ation (T3n -r vl) rests Form ation A fter that, the lim estone o f the D ong D ang F orm ation w as d eposited in the u ncon form ably m arine en vironm ent, at a transgressive tim e in stan ce the O rd ovician Phu N gu Form ation, correspond ing to the C han ghsin gian Thus, the the C a m ia n N a K hu at Form ation (T3c ms) T he bauxite and other com p onents o f the D ong u pon H on G older sed im ents F orm ation for hg) (T3n -r D ang F orm ation w ere d eposited in different u ncon form ably rests u p on Low er P aleozo ic Tan environm ents, and the com bination o f them in M one form ation is tem porary only lim estone Form ation The Su oi or Bang unconform ably Mesozoic unconformities and gaps u pon U p p er Form ation rests u pon P aleozoic sb) (T3n-r m any older form ations, from Proterozoic (Sin Q uyen, Nam Co In the north o f V iet N am , the num bers of u nconform ities in M eso zo ic stratigraphy have been recorded, and the m ain ones could be form ations) Form ation) and to A nisian even (D ong C am ian Giao N am Mu Form ation (Fig 7, Fig 8) Mt Chu 316" Xom Mu listed as follow s H ie Hong N gai Form ation (Ti hn) and its synchronous Lang So n F orm ation (T ! Is) appear to conform overly w ith D ong D an g Form ation (P32 dd), though (characteristic conodont parva the zone of the lo w er Zone Triassic boundary) has n o t b een found, so a short depositional gap could happen In the w est o f Bac Bo, the C o N oi Form ation lies u nconform ably upon the Y en D uyet Form ation (P3 yd) The u ncon form ity Song H ien D ong D ang T he H a C oi F orm ation (JN2 he) covers w ith Form ation (P32 dd) has b ee n observed in the an gu lar u ncon form ity L ow er P aleozoic bed s of sections located in the w est o f C ao Bang Tow n the Tan M Form ation A s in Thai N guyen City, and in Binh G ia area (Lang Son Province) these bed s lie u nconform ably u p o n N orian - Form ation (T! sh) of u pon the Fig The Chu Mt - Xom Mu Hamlet Section, km southwestward from Hoa Binh Town, shows the angular unconformity of the Suoi Bang Formation (T3 n-r sb) upon the Dong Giao Formation (T2 a dg) illustrated by Tran Van Tri the The Lan P ang F orm ation (T2a Ip) rests unconform ably u pon the L o w er T riassic Song H ien F orm ation or U p p er P aleozoic lim estone T h e effusive K h o n L an g F o rm atio n (T2a kl) R h aetian coal-bearin g V an L ang Form ation The Yen u nconform ably Chau rests Formation u p on (K2 d ifferent yc) older sedim ents P erm ian The N am M a F orm ation (K nm) and the B an lim estone and the L ow er Triassic Bac Thuy H ang F orm ation (K bh) u nconform ably cover Form ation d ifferent old er sedim ents, for exam ple N am Po rests u nconform ably The Yen Binh upon U p p er Form ation (T2a yb) rests unconform ably w ith basal conglom erate upon the Ha Giang Form ation (€ hg) The M au Son Form ation (T3c ms) appears to (j! np) and H a C oi (J,_2 he) form ations The L ate F orm ation T riassic Ju rassic effusive u nconform ably Tam lies u p o n L ung L ow er terrigenou s bed s o f the L an g Son underly unconform ably the coal-bearing Van F orm ation, as w ell as u p on M id d le Triassic Lang Form ation (T3n -r vl) form ations Tong Dzuy Thanh i VNU Journal of Science, Earth Sciences 23 (2007) 137-146 144 CHRONOWEST NAM BO & STRATIGRAPHY GULF OF THAILAND Ta I Hon I Dat Not jQ u a n i Do PERMIAN M ID TRUNG BO VIET- LAOS W EST BAC BO EAST BAC BO QUANG NINH Dong Dang Bai Chay Cam Lo Chu Prong m in i] ; Ha Tien Da Mai Ban Diet Dak Lin Da Mai CARBONI­ FEROUS Da Mai La Khe Phong Ị Son , Xom Nha " Thier - - — Nhan D, Da Nieng Nam Can Lung Nam Con Voi Toe Tat Toe Tat Dong Tho Pho Han I Bang Ca Bang Ca Mue Bai DEVONIAN D« Ban Giang Ban Pap Huoi Loi Ban Pap Ban Nguon _ Mia Le Song Mua S o n a lBac Bun Bo Hieng T T tm r Hon Heo Cu Brei Rao Chan A Choc Dai Giang SILURIAN Nam Pia Tay Trang Song Ca csUliaiJTJTJII K ienAn Co To Phu Ngu Sinh Vinh Long Dai Duong Dong Tan M a i' Na Mo ORDOVI­ CIAN Phong Hanh A Vuong Ham Rong CAMBRI­ AN TTTTTTT Lutxia Dong Son Ben Khe Chang Pung Than Sa Ha Giang Song Ma Cam Duong S o n g C y NEOPROTEROZOIC G ro u P An p fu jThac Ba Fig Stratigraphic correlation of Paleozoic Units in Viet Nam From above m entioned u nconform ities and phase took place in N orian of L ate Triassic by gaps, the N orian-R haetian is the m ost interesting the collision o f the M alaya plate w ith the one because it m arked a new period in the Indochina T his angu lar u nco n fo rm ity has been geological largely record ed not only in V iet N am , bu t also developm ent of V iet N am and Sou theast A sian in com m on In the tectonic in Sou theast A sia and So u th C hina, so there is differentiation o f the B ac Bo region in M esozoic, no need to d iscuss m ore abou t it other unconform ities p ro b ab ly are local ones The u nconform ity o f L ow er D evonian Si Ka F orm ation and Song Cau G roup upon L ow er P aleozoic form ations is an im portant Discussion and inclusion one, bu t its role in regional g eology has not yet been The angu lar u nco n fo rm ity o f Suoi Bang, p roperly stratigraphic accessed gap of by L ate geologists The O rd ovician and V an Lang, and H on G form ations of N orian- Silu rian largely occurs n o t only in the north of R haetian N orth V iet N am (V iet B ac in V ietnam ese), but age u pon variou s form ations of different ages is an im portant event in regional also in G uangxi and geology; it m arked th e ch an g e tectonic regim e China T h e red bed s facies sedim ents (Si Ka of indosian Form ation in V iet N am and L ianh u ashan in orogeny in V iet N am and in Sou theast A sia in South C hina) also largely extend in the sam e com m on areas the region T he resu lting from in d osinian the m ovem ent has happened from P erm ian , bu t the intensified w ith Y u n nan u nco n fo rm able provinces of relations upon Low er Paleozoic By lith olog ic characteristics of Tong Dzuy Thanh /VNU Journal o f Science, Earth Sciences 23 (2007) 137-146 145 rocks such as red color, coarse grain and cross and D on g D an g form ations are com posed of bedding and ligh grey, thick bed d ed lim estone containing m icrovertebrate fossil rem ains, these form ations abu ndant foram inifers T h ere is no expression can be referred to flu vial and continental facies o f an orogeny in Perm ian, and the unconform ity It is reasonable to com p are these form ations betw een D ong D ang and Da M form ations w ith w ould be influenced by the local raising only sedim ents, Old deposits Red and San d ston e p lant in in W est Europe epicaledonian From the above M any other u nconform ities and gaps m aterials, su pposing that the north of North even w ith conglom erate in the bottom of the V iet N am (Ha G iang, C ao Bang, Lang Son, and overlying Thai N guyen provinces) and Sou th C hina w ere perhaps are only local unconform ities A m ong form ation are in Paleozoic, not regional, there are the Nam but under influence o f the C aled on ian M ovem ent them (Guangxi M ovem ent by C hinese geologists), Form ation ones th at overly and during pre-D evonian, the terranne w as Form ation and raised in som ew here northw ard from the north Form ation w ed ging the Ban Pap Form ation, the Pia the D ong Son tongue-shape Tan Lap of N orth V iet N am In D evonian, the north of and North V iet N am w as the southern m argin of a u nconform ities in M esozoic, except the N orian- continent, Rhaetian, are also the local ones w here alluv ial and continental m any others P erhaps alm ost all deposits took place In conclusion, supposing that the unconformity o f Low er D evonian upon Low er P aleozoic form ations A ck n o w led g em en ts was influenced by the Caledonian movement, and it should be an im portant regional one in the north o f North Viet Nam and South China This paper w as com p leted w ithin the fram ew ork o f the R esearch Project 703306 in the Perhaps the continental regim e in South field of Fund am en tal Sciences The author is China had not long existed, and at the beginning grateful to the C ouncil o f N atural Sciences and of Late Lochkovian (Bac Bun in V iet Nam, its Earth Science B ran ch (V ietnam M inistry of Nagaoling in South China) the terrane had been Sciences and T echnology) for their valuable gradually subm erged From th at tim e forw ards, support the been gratitu de to Prof Vu N goc Tu for assistance in dom inated in the terrane, and in this basin fin e­ im provem ent of the English version of this grained paper, to Prof T ran V an T ri for illustrating the shallow and m arine environm ent carbon ate has sed im ents contain abundant organic rem ains w ere deposited T he gap betw een D a M and D ong D ang form ations is a short unconform ity, and it The au thor expresses his deepest N orian-R haetian angu lar unconform ity, to Mr Tran Th anh H a (Institute of V ietnam ese Studies and D evelopm ent Sciences) and M s N guyen lasted during the W u ch iap ing ian (last tim e of Thu M iddle Perm ian) only N ew data of D oan N hat figures Cue (C ollege of Science) for draw ing Truong researches show th at the D a M age could last up to W u ch iap in gian , in this case the gap is even shorter - in range o f tim e betw een R efere n ces adjoining W u chiap in gian and C hanghsingian stages o f U pper Perm ian T here is no facial change in u nd erlyin g and overlying form ations, except the thin low erm ost bed s of the Dong D ang Form ation, alm ost all adjoining Da M [1] Bui Phu My (Ed.), Geologcal Map 1: 200,000 o f Lao Cai - Kim Binh Sheet, Vietnam General Department of Geology, Hanoi, 1978 (in Vietnamese) [2] Dang Tran Huyen, Nguyen Kinh Quoc, New data 146 [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] Tong Dxuy Thanh /VNU Journal o f Science, Earth Sciences 23 (2007) 137-146 on the Triassic stratigraphy and paleontology in the An Chau facial-structural Zone, Geology and Mineral (2000) (in Vietnamese) J Deprat La succession des horizons paléozoiques dans la région de Hoabinh et de Chobo, Bulletin du Service Géologique de l'Indochine II/l (1913) 14 A.E Dovjikov et al., Geology o f the North o f Viet Nam, Vietnam General Department of Geology, Hanoi, 1965 (in Russian) Duong Xuan Hao, Nguyen Thom, Nguyen Due Khoa, New data on biostratigraphy of Middle Paleozoic deposits (1964 to 1973), in Selected works on stratigraphy, Science and Technology Publishing House, Hanoi, 1975 (in Vietnamese) Doan Ky Thuy (Ed.), Geological and Mineral resources map 1:200,000, Lang Son sheet, Department of Geology and Minerals of Vietnam, Hanoi, 2000 (in Vietnamese) Doan Nhat Truong, Dang Tran Huyen, Nguyen Xuan Khien, Ta Hoa Phuong, On the Permian/Triassic boundary in Vietnam, Journal o f Geology B/24 (2004) J Fromaget, Sur les plissements calédoniens du massif du Fansipan (Tonkin), Comptes Rendus de l'Académie des Sciences de France 195 (1932) 552 J Fromaget, L'Indochine franỗaise, sa structure géologique, ses roches, ses mines et leur relation possible avec la tectonique, Bulletin du Service Géologique de l'Indochine XXVI/2 (1941) 140 Hoang Xuan Tinh (Ed.), Geological and Minerai resources map 1:200,000, Bao Lac sheet, Department of Geology and Minerals of Vietnam, Hanoi, 2000 (in Vietnamese) Luong Hong Huoc, Tran Huu Dan, Dam Ngoc, Division and correlation of the Upper Proterozoic and Lower Paleozoic stratigraphy in Ha Giang and Vi Xuyen areas Journal o f Earth Sciences 18/1 (1996) 44 (in Vietnamese) Ma Li-fiang et al., Geological atlas o f China, Geological Publishing House, Beijing, 2002 (in Chinese) I Metcalfe, Southeast Asia, in Encyclopedia o f Geology Ed by R.C Selley et al., Academic Press, 2005 [14] Nguyen Huu Hung, Doan Nhat Truong, Dang Tran Huyen, New data on Devonian deposits in the Bac Son Massif, Journal o f Earth Sciences, 3/2 (1991) 33 (in Vietnamese) [15] Nguyen Xuan Bao (Ed.), Geological map 1:200,000 Van Yen sheet, Vietnam General Department of Geology, Hanoi, 1978 (in Vietnamese) [16] Nguyen Vinh, Late Silurian - Devonian deposits in the West Bac Bo Region of Vietnam, in Problems o f geology in the west Bac Bo region o f Vietnam, Science and Technology Publishing House, Hanoi, 1977 (in Vietnamese) [17] Pham Dinh Long (Ed.), Geological and Mineral resources map 1:200,000, Chinh Si - Long Tan sheet, Vietnam General Department of Geology, Hanoi, 2000 (in Vietnamese) [18] Pham Dinh Long (Ed.), Geological map 1:200,000, Tuyen Quang sheet, Vietnam General Department of Geology, Hanoi, 2001 (in Vietnamese) [19] E Saurin, Lexique stratigraphique International, Asie 6a Indochine, CNRS, Paris, 1956 [20] Tong Dzuy Thanh, Vu Khuc (Ed.), Stratigraphic units o f Vietnam, VNU Publishing House, Hanoi, 2006 [21] Tran Van Tri et al., Geology o f Viet Nam Northern Part, Accompanying notice on the Geological Map (1:1,000,000), Science and Technology Publishing House, Hanoi, 1977 (in Vietnamese) [22] Vu Khuc, Bui Phu My (Ed.), Geology o f Viet Nam Vol I Stratigraphy, Vietnam General Department of Geology and Mining, Hanoi, 1990 (in Vietnamese) [23] Wang Hong-chen et al., Atlas o f the palaeogeography o f China, Cartographic Publishing House, Beijing, China, 1985 [24] Wu Yi et al., Sedimentary facies, paleogeography and relatively mineral deposits o f Devonian in Guangxi, Guangxi People Publishing House, Guangxi, 1987 (in Chinese) [25] Yang Si-pu, P Kiang, Hou Hong-fei, Devonian System in China, Geological Magazine 118/2 (1981)113 VIETNAM NATIONAL UNIVERSITY, HANOI JOURNAL OF SCIENCE EARTH SCIENCES Vol 23, No 3, 2007 CONTENTS T o n g D zu y T h a n h , O n som e significant u nconform ities in th e P aleozoic and M esozoic stratigrap h y o f N orth V iet N am N g u y en D in h M in h , B u ild in g a G IS database for ecotourism d evelo p m en t in B a V i D istrict, H a T ay P rovin ce, V ietnam 137 147 N g u y en N goe K h o i, N g u y T u y e t N h u n g, N g u y en T h i M in h T h u y e t, P h a n V a n Q u y n h , C haracteristics o f coru ndum s from Phuoc H iep o ccu rrence (Q u ang N am Province) V u T h a n h C a, A nu m erical m od el for the sim ulation o f w av e d ynam ics in the su rf zone and n ear co astal structu res 153 160 N g u y en T h a n h L an , T n N g h i, D a n g M a i, D in h X u a n T h a n h , C haracteristics o f Q u aternary sed im en tary facies in relation to w ater bearin g cap acity o f aqu ifers and aqu iclu des in th e R ed R iver D elta, V ietnam 170 V u D u e M in h , N g u y en B a D u an , Som e results o f d iscovering old vestiges in the vicinity o f K inh T hien T em p le 177 T a H oa P h u o n g , T w o F rasnian/Fam ennian boun d ary sections in V ietn am 187 D an g M a i, V u T h a n h L an , Q uantitative d istribu tion o f g ro u n d w ater chem ical com ponents in the R ed R iver D elta based on frequ en cy an alysis 194 INSTRUCTIONS TO AUTHORS Serial Earth Sciences o f the Jou rnal o f Science o f V ietnam N ational U niversity, H anoi qu arterly pu blishes A d m inistration, research articles M eteorology, in H ydrology, the fields of G eology, O ceanography, G eography, Environm ental Land Science, Subm itted m anu scripts are accepted on the basis that they have n o t been, and w ill not be, published elsew here M an u scrip 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Department of Geology and Minerals of Vietnam, Hanoi, 2000 (in Vietnamese) Luong Hong Huoc, Tran Huu Dan, Dam Ngoc, Division and correlation of the Upper Proterozoic and Lower Paleozoic stratigraphy. .. p on Low er P aleozo ic Tan environm ents, and the com bination o f them in M one form ation is tem porary only lim estone Form ation The Su oi or Bang unconform ably Mesozoic unconformities and. .. tectonic regime of the region resulting from the indosian orogeny in Viet Nam and in Southeast Asia in common The gap of Lower Devonian red beds formations (Si Ka Formation, Song Cau Group) upon