đặc điểm phát triển bờ và dao động mực biển hologen ở khu vực hải phòng

T~p chi Khoa hQcva Cong ngh~ bi~n, T4 (2004), S6 3, Tr.25-42 D!C DIEM PHAT TRIEN BO vA DAODQNG MVC BIEN HOLOCEN o KHU vvc HAl PHONG TRAN DUC THANUC') DINH VAN HUy(1), NGUYEN CAN(2), DANG , DUC NGA(2), a Tom tat Ve' co'bdll cae kiell tnte lIinli thai dl(o'ngva am kllll v~(eHdi phong phdt trie'n ke'tlllfa trell 1Ie'1Icae diJi kiel! tnte nang vd II~ ta/l kiell t~o va kiell t~o lIi~1Id~i TllY IIlIihl, kiell tnie Ilillll thai am VJllIgeli-asO/lg Bgell Dallg phat trie;1 ma rqng nJqt pluln cd trell lIe'n dili na/lg die'll hoa Do IiI kef qlld dnll III(allg elia biei! tiell eMII tlnll Holoeen a /IIqt kllll v~(even bi! dia Ilillll bi ehia edt m~nh Trong Holoeell, S~(phat trie;1 elia kllll vl/e ven bi! chill S~(chi pll6l elia qllan h~ fI(o'lIgtae Clia eIlllye;1 dqllg kiell tgo, S~(thay ddi m~(e bie;! eMn tlnh va qlla trillh tl'll/11tiell Co SI/ khae bi~t filII ve' he' ddy tra/ll tiell Holoeen tllllqe cae h4 ta/lg Hdi Ha/lg (QI\' 1-2IIh) va Thai Binll (QI\'.I tb) tre/l eae dili nang va II~ kiell t~o khll v~(eDong Bde, tra/ll tiell eIlli yeilla cae tl(ilng da/ll hl~ySit vl/t va trie'll tMp rat hii'm g{ip cae filp mong tl(iI/lg dl(Ji trie'll Trell cae dili na/lg m~nll va /IIqt pllall nallg die'll hoa, tram tieh Clia cd Iwi II~ tang IIdIl nlll( chi lei fl(iI/lg dam My \"ItVl/t.Tat cd cae tlle,n tieh bie;1 b(;k I (3-3.5m) tlldi dall Holoee/l mllqn, II (4-6m) tll& gii(a Holoeen giii'a, III (8-12m) tllbi ellol Pleistoeen 11IIIqllva cae ngall an //Ion bie;1 co dq eao tl(o'ng d'(o'ng tren vaeh da voi de'll nal11 tren cae dili nang kiell t~o hi4n d~i Co h~ de cat eb Holoeell dl(t!e Ilinll trollg qlla trinh tiell IIoa bi!, phd/l anll khd ro SI/ tllay d& tl(o'/lgdOl Clia "ll/e bie;/ H~ eao 4-6m, tll6i giii'a Holoee/l giii'a; 114 eao 3-3,5111,tllbi dall Holoee/l "lIIq/l; h4 eao 2-2.5m tllbi giira Holoeen mllqn; 1144 eao 2,5-3m, tllbi ellol Holoeen IIlIIqn va h~ eao 3-3.5m tll& hi411 Trong h4 tM( nam giii'a, tMI) IIMt, tllbi klwd/lg /lgllinnam tmile SI/IlIi, Mil Clia d,(i!/lg bi! I1Iqtso'Mn trollg tlf/lg giai dO~1Ike' flf sail IIgllin nam eIlli yell qllall h4 gifia toe dq M/lg d{mg tral1l tiell vd Sl/ dao dqng m~(e Il/(ile bie;1 nlll( IiI kef qlld tbng ht!p Clia eIlI/ye;1dqng kiell t~o va na/lg eM/I tl/lh Dao dqng ml/e Il/(ile bie;1 tl/lh kllll v~(etro/lg Holoeell d,(t!e eIlI(ng to la na/lg eao dall eIw dell Trong do, m~(eJ//(ile tl(o'/lgdOl-vi tri dai!/lg hi! thay (Mi dao dq/lg hillll sin tlleo bie/l dq /1110dan qlla tr~le /III/e hie;, t,."ng hi/lll lIi4/1/lay Vi tri lIll/e J//(ile bie;! tl(o'/lg dOl eao nMt +4-6m vdo tllili gia/l 5-6 ngllin /lam tmile, sail II~ thap ho'n hi4/f7lay 2,5-4m VaG 3-4 /lghin /lam tn(iIe, tl(o'ng.I(/lg tll6f elia van hod He; Lo/lg va di chi khdo eb Trang Kenll Tiel) tlleo, vi !ri ml/e J//(iletl(o'ng dOlndng eao llo'n IIi4nnay 3-3.5/11 VaG2-3 nghinnam tn(ile roi h~ da'n thai) IIo'n IIi4nnay 1,5m vdo kllodng nghin lIa/ll tmile, sau nang dan dell Nhom ea dan eb Vi4t Klie pllan edell ve' tllili giall viii el( dan eb Trdng Kenh qlla dt!t hie;, Mn vdo 2-3 nghin ndm tmile Vao klwdng ngllin na/ll tn(ile, m~(e bie;1 tl(o'ng dOl IIg thai) nhat Holoeen IIII/qn /IIa dong being ehall tllb song Hong it bi Iii nglJp nhat _Mqt nghin nam qlla, eMII thb a kIll/ vi/e Tay Na/ll Hdi Phong vdll tiel) t~le boi Mn bie;I, die'" ki4n /II~(ebie;1 dang eao nlll(ng nM llo'n toe dq Mng d{mg tram tieh Klwdng 5-7 ti'am nam tmile Do So'n gdn viii dong bang b6i tl./de' hiell thanll Mil ddo Tlf do, vllng Cli-asong B~eh Da/lg eIlllye;1hod tlf elli'dq eha" tll6' (delta) eo dql/g I~(esong th6'lIg tri, sang eIuJ'dq Ilinh plu?u (estuary) co dqng h/e bie;1 tllo'ng trio Cd ba trlJlI tllll.v ehiell Bgeh Dang a tile' ky X-XlII (lell xdy klli vllng da B~eh Dang can a elle'dq ehall tllb,-bi! Mil xa llo'll phia hie;1 va long song nong, II~p 110'11 hi4nnay a 25 I MO DAV Hai Phong co vi tri d~e bi~t, nam ehuy~n tiep giUa ven bo Dong B~e va eMu th6 song Hong, giUa kien true Caledolit va trung dia hao Kainozoi Do dia hinh ven bo da disoi noi dim b Do San va Ao Coi - Cat Ba d Ao Coi them dllac cau tao bbi cat, san, cuoi chua manh san ho, vo than m~m bien va da cuoi bazan d Do San th~m dllngcl!c d~i vao khoang 5-6 nghln nam truac Them tich t~lbien btjc I Holocen mll91l(Qr/) tren dtli ndng va ndng die'llhoa, cao 33,5m, cau t~o tu cat nho, s~n, cu(>i,mai tron, chQnIQctot, chua than m~m bien, t1lOOgbai bien, tu6i khoang 2.000-3.000 nam truac Chung g~p 6'nhi~u nai nhll Do San, Cat Ba, B~chLong Vi, hi~n dang bi x6i 16'ph6 bien s6ng bi~n Cae h~ th{ing de eat bien H~ J : cao 4-6m, tllang dllang them tfch tl,lb~c II, tu6i Holocen giii'a,cau t~o.tu cat trung va tho, keo dai tu Tien Lang (Kh6'i Nghia, Tien Tien) qua Quoc 1(>10 (Thuy Nguyen) va tiep tl,lcsang Quang Yen H~ 2: cao 3-3,5m" tllang dllcmgth~m tfch tl,lb~c I, tu6i dau Holocen mu(>n,khoang 2000-3000 nam truac, cau t~o b6'i cat h~t nho mau xam vang, xam nh~t, phan bo sat h~ de cat II 6'Thuy Nguyen, tiep tl,lCkeo tai lang An Bien c6 6' n(>ithanh roi sang Kien An, Tien Lang: H~ 3: cao 2-2,5m, tu6i giii'aHolocen mu(>n,khoang 2000-1000 nam truac, cau t~o b6'icat h~t nho mau xam vang den xam nh~t, phan bo tu Phu Long, Cat Hai sang Trang Cat va tiep tl,lc6'Kien Thl,ly, Tien Lang H~ 4: cao 2,5-3m, tu6i cuoi Holocen mu(>n,khoang 700-500 nam truac, cau t~o b6'i cat h~t nho mau xam, xam vang, phan bo tu Do Sem, Kien Thl,lysang Vinh Quang (Tien Lang) H~ 5: cao 3-3,5m, tu6i hi~n nay, cau t~o b6'icat h~t nho mau xam nh~t, vang nh~t, phan bo 6'ven ba Dllqng Gianh, Cat Hai, Dlnh va va Vinh Quang 33 Nhu v~y, theo m~t cat ngang phfa bi~n, dQcao cac de cat giam d~n tir h~ den h~ chUngminh cho qua trlnh h~ thap tuong doi mt!c bi~n va dQcao tang d~n tir h~ den h~ chUngminh cho qua trlnh nang cao tuong doi mt!c bi~n [7] Cae them mai mon va ngan biln cd Them mai man (bench) duqc hinh duai chan vach doc gi~t liJid~n cua vach duai tac dQng cua song bi~n va co dQ cao ngang mt!c nuac bi~n duong thai Duqng Gianh, Cat Hai, Dinh Vu co cac them rQng 20-50m, cao 0,4-2m phat tri~n tren nen tr~m tfch ba rai ba dang bi xoi la O'Do Son them mai man phat tri~n b~c co dQ cao khac nhau: b~c tren cao 2-2,5m ngang mt!c bi~n d~u Holocen mUQn,b~c giUacao ngang mt!c bi~n trung binh hi~n va dang pMt tri~n, b~c thap cao -0,5 den -1,Omso vai mt!c bi~n trung binh, co Ie Ungvai mt!c nuac h~ thap vao khoang nghin nam truac Cac ngan bi~n c6 Holocen 4uai d~ng cac ham ech t~o an man hoa hQc cua nuac bi~n va song vQ.trenvach da voi Cat Ba va H~ Long da duqc xac dinh co hai ngan chfnh [18, 23] Ngan tren cao 4-6m (so vai mt!c bi~n trung binh hi~n nay), tuong duong them bi~n b~c II, ung vai mt!c bi~n tuong doi nang cao nhat vao giUa Holocen giUa, khoang 5-6 nghin nam truac Ngan duai cao 3-3,5m, tuong duong them bi~n b~c I, Ung vai mt!c dinh cua dqt bi~n Ian vao d~u Holocen mUQn,khoang 2-3 nghin nam truac G~n day, nhilng so li~u tu6i tuy~t doi mai co a vinh H~ Long va Ninh Binh cung cho thay ngan tren tu6i t~p trung vao 5-6 nghin nam truac va ngan duai la 2-3 nghin nam truac [10] T~i vung ba da voi Ha Tien a phfa Nam, cung ton t~i hai ngan an man bi~n Ngan tren cao 4,5m cung co tu6i tuy~t doi 5-6 nghin nam truac, nhung ngan duai cao 2,5m, kMc vai khu vt!c Hai Phang-H~ Long, co tu6i 4150 nam truac [13] IV D~C DIEM PHAT TRIEN VUNG VEN BO TRONG HOLOCEN Cuoi Pleistocen ~uQn co m~t dqt bi~n tien vao yen ba Bac BQva rut da t~o tr~m tich thuQc h~ t~ng Vinh Phuc yen ria doi nui a Do Son,Cat Ba da hinh cac them tich tl;1bi~n b~c III d~ng noi dao, tren vach da voi qu~n dao Cat Ba, Long CMu va a Thuy Nguyen can dau tich cac ngan mai man bi~n co dQcao 8-12m MQtso gia tri tu6i tuy~t doi cua cac ngan da duqc xac dinh, tre nhat la khoang 33 nghin nam truac [10] Sau la thai ky bi~n lui, lien quan den dqt bang l~n cuoi, duang ba tien ngoai elra vinh Bac BQ.Be m~t dong bling Vinh Phuc viraduqc t~o bi phong hoa m~nh co mau sac loang 16.Qua trinh song ho~t dQngm~nh da xam cat be m~t day Vinh Bac BQ, t~o nen m~ng thung lUngsong c6 bi ng~p chim co d~ng canh cay va h~u het co huang noi vai cac song tren Il;1cdia hi~n Sang Holocen, bi~n tien xuat phat tir dQsau 100-120m, toc dQluc d~u kM Ian va sau ch~m dan Trong qua trlnh bi~n tien co mQtso l~n thay d6i toc dQdo nguyen nhan 34 thuy tinh toan dIU va co imh huang cua hO:;1t dQngkien t:;1otrong ph:;1mvi vung triing Ha NQi Bi~ntien thai gian Holocen s6m- giiia t:;10ra tilng trilm tich Hai Hung ph6 bien tu60g trilm tich dilm lily su vyt va,bai tri~u thap Bi~n ma rQng C1;rc d:;1ivao khoang giiia Holocen giiia (5-6 nghln nam tru6c) TreingHai Phong la mQt vinh nong Hu6ng vong cung Tay Bac-Dong Nam, Dong Bac-Tay Nam cua cac dai d6i nui da t:;10nen ki~u ba dalmat a phfa Bac.; RIa Tay Nam thuQcvang Ha NQi la mQtvinh bi~n 160han D6i nui a Thuy Nguyen, D6 Son -Kien An va Cat Ba la cac dao ven ba Dau vet dqt bi~n tien can duqc ghi l:;1inhi~unoi tren vach da voi quilndao cat Ba, TrangKenh,Nui Voi du6i ' d:;1ngngan an man, xam thl!cmai man bi~nva vo hiluha c6 barn a dq cao 4-6m (hlnh 3) Cuoi Holocen giiia,duang ba dich diln phfa bi~n cung v6i sl! t:;10cac de cat h~ I keo dai tir Quang Yen, Nui Deo den Khai Nghia (Tien Lang) Khoang 4000-3000 nam tru6c d6n~ biing ll)c dia ven bi~n da duqc thiet l~p a Hili Phong Tren m~t cac t:;1ode cat cua h~ I dii t:;1ora mQt.l6'pmang laterit g~p a Quang Yen va Tien Lang Du6i m~t bai tri~u hi~n d:;1i(sau'2,5 - 3m) aCat Hai, Dlnh Vii thuQCd6i h:;1tUang doi m:;1nhda bat g~pcac trilm tich than bun ll)c dia ven bi~n d:;1ngthau kfnh [20,21] Trong Holocen mUQn,duang ba bi~n Ian tra l:;1ivao chirng 3000-2000 nam tru6c Bi~n Ian t:;1ora mQt vinh m6i di~n tich khong khac nhi~u so v6i Holocen giiia nhung nong han Cac tich tl) cat song va dong d9Cba da noi li~n cac dao nha rieng bi~t a D6 San mQt dao nhat (trirHon Dau), noi li~n Nui Doi v6i Thuy Huang va t:;1onen cac th~m bi~n hyp, cao 3-3,5m a Cat Ba Sau do, d6ng bang l:;1ib6i tl)lan bi~n, song vun tl) cac de cat thuQch~ II phan bo kha sat v6i h~ 1.a Ben Giang (Quang Yen), trilm tich cat cua dqt bi~n Ian da phu trum len 16platerit cua h~ tilng Hai Hung Vao khoang 2000-1000 nam tru6c ba bi~n tiep tl)c tien phfa bi~n toc dQtrilm tich 160 han t6ng toc dQnang chan tinh (0,06mm/nam) va toc dQh:;1lUn(0,2mm/nam) cac d6i Sl)t h:;1.Ngu6n b6i tich cung cap tir Song H6ng len phfa Bac kha phong phu, da t:;1onen h~ de cat III cao 2-2,5m keo dili tir Phu Long, Cat Hai sang Dlnh Vii, Trang Cat, Tan Trao, Toan Thang, cd' Am Day la h~ de cat keo dai lien tl)c nhat, nhung ceingthap nhat a ven ba Hai Phong, danh dau vi trf tUangdoi duang ba - ml!c bi~n h:;1thap nhat MQt nghln nam qua, ml!c nu6c bi~n dang nhanh diln VI the, qua trinh ng~p chlm khong chi xay tich cl!Ca ph:;1mvi hyp cua b6n treingSl)th:;1ma phat tri~n cii a philn ria co che dQkien tn(5-7 train nam qua), bi~n Ian vao h,lcdia phia Dong Bilc ban dao Do San toc d(>t6ng hqp Sl,ltchlm (0,2-0,8mm/nam) va dang chan tinh (0,5 1,5mm/nam) vuqt toc d(>lilng dqng trftm tfch (0,6-1,6mm/nam) Cac dao Phu Long, Cat Hai, Dlnh Vii bi xoi la thu h~p di~n tfch San phiim pha huy duCJcsong va dong tri~u len tfch tl,l h~ de cat V cao 3-3,5m sat ba Tay dao, dqc dra Nam Tri~u, Li;\chHuy~n khu vl;l'cTay Nam tfch tl,l,chau th6 viin tiep tl,lcboi tl,ltrong di~u ki~n ng~p chlm co d~n bu boi tfch Tuy nhien, toc d(>boi tl,la day khong d~u va co nhilng pha boi-xoi xen ke chu ky ngiln Khu ba B~ngLa, Vinh Quang may chl,lcnam truac bi xoi la mi;\nh,hi~n dang co xu the boi tl,ltra li;\i.Cua song Van Uc dang co xu the hlnh pMu hoa a v DAO DONG MVC NUOCBIEN HOLOCEN Bi~ntien sau bang Iftncuoi bilt dftu ttr khoang 17 - 18 nghln nam truac, ttr d(>sau 100 - 120m tren them ll,lcdia Co'ba quan di~m khac v~ dqt bi~n tien (hl~h 4) Fairbridge (1961) choOr~ng, ml;l'cmrac bi~n di;\tden d(>cao cl;l'cdi;\i3 - 4m vaokhoang5 - nghln nam truac, sau dao d(>nglen xuong nhi~u Iftn cho den hi~n Trai li;\i, Shepard (1963) li;\icho r~ng, ml;l'cnuac dang cao dan cho den hi~n Quan di~m thu ba, co Fisk (1957) cho r~ng ml;l'cbi~n dang cao b~ng hi~n va 6n dinh suot 7-8 nghln, 5-6 nghln ho~c 3-4 nghln nam truac Gan day, tren quan di~m thuyet thuy dAng tinh, co xu huang mai cho r~ng ml;l'cnuac di;\iduang dao d(>ngkhac ttr khoang 6-7 nghln nam tra li;\iday a cac khu vl;l'ckhac tren trai dat [11] va ca ba quan di~m tren d~u co tM dung a ttrng khu vl;l'cCl,lthl Vung phia ban cftu Bilc cua Tay Thai Blnh Duang co ml;l'cbi~n cao nhat vao 5-6 nghln nam truac roi hi;\thap cho den hi~n Vung Nam ban cau, di~n hlnh la di;\ill,lcAustralia, ml;l'cnuac co th~ di;\ttai muc hi~n ttr 3-4 nghln nam truac va ca ban 6n dinh cho den bay gia [17] Cac vung Tay Au [8], Bilc Phi [16] va BilcMy [15] co ml;l'cbi~n dang cao dftn suot Holocen cho den hi~n Co th~ dan vi dl,l,v~ dao dOng ml;l'c nuac ti;\i m(>t so vung a hi;\ luu song Nile (Ai C~p),theo Stanley va Warne (1993) ml;l'cnuac Holocen dang cao dftn cho den hi~n va cMu th6 bilt dau duCJcboi tl,lttr 7500 nam truac Ml;I'C nuac vao 6500 nam truac thap han hi~n 9-1091 va 2000 nam truac thl thap han hi~n 2m [16] a vinh Botany (Australia), theo Roy va Crawford"(1979), ml;l'cbi~n 9-7 nghln nam truac dang ttr d(>sau 12m den 9m; 7-4 nghln nam truac dang ttr d(>sau 9m den vi tri nhu hi~n [17] Theo Nguyen Van L~p, Ti;\Thi Kim Oanh va Tateishi (2000), a dong b~ng song Ciru Long, ml;l'cnuac Holocen cao nhat 4,5m vao 5-6 nghln nam truac, sau hi;\thap dftn cho den hi~n [13] Rat dang luu y la tai li~u dao d(>ngml;l'cnuac chau th6 Truang Giang (Trung Quoc) Theo Chen va Stanley (1998), nhilng nghien cUutruac day d~u cho r~ng a ml;l'cnuac Holocen a dong b~ngnay a muccao 3-5mkeo dai 7-4 nghlnnam truac, 36 sau h~ thap diln chp den hi~n"nay.Nh6m tac gia da tmh toan l~i s61i~u cua cac bi~u d6 da co, xac dinh tuOi them tuy~t d6i cac 16 khoan mai va di den ket lu~n rfing.mt!c mrac dang cao lien U;lc den hi~n nghln nam qua va vao nghln nam tnrac thap hon hi~n 9-lOm, va vao 4,5 nghln nam truac thap hon hi~n 5m HQda khao sat It!achQn28 s6 hon 300 di chi khao cOda mai co nien d~i 7-3 nghln nam truac t~p trung a h~ luu phfa Nam song Truang Giang va di den nh~n dinh rang b6 m~t dinh cu cua cu dan cOnfimtrong khoang dQcao ttr -3 den +3m [3] d Vi~t Nam truac.day phO bien quan di~m cua Saurin E, cho rang mt!c bi~n Holocen cao nhat 4m vao 4500 nam truac va h~ thap diln cho den hi~n Den nay, tai li~u tfch luy duQ'ccho thay mQt buc tranh khac TOnghQ'ptai li~u da co v~ dia m~o, kien t~o, dia tilng- tuang trilm tfch, mQts6 tuOituy~t d6i va tham khao tai li~u khao cO-lichsu, st! thay dOimt!c nuac tuong d6i - vi trf ducrngba khu Vt!CHai Phong ki~u dao dQnghlnh sin vm bien dQ nho diln ttr Holocen giiia den da duQ'cTriln Duc Th~nh d~ xuat nam 1993 [22] Tai li~u khao sat va nghien coo bOsung cang khAngdinh va chfnh xac hoa ket qua nghien cuu Vao khoang 7-8 nghln nam truac, mt!c nuac thap hon hi~n 1014m Mt!c nuac tuong d6i cao nhat +4-6m vao 5-6 nghln nam truac, sau h~ thap tuong d6i 2,5-4 m vao 3-4 nghln nam truac, dang cao tuong d6i den +3-3,5m vao nghln nam tnrac, tiep tl;lch~ thap den -1,5m.vao nghln nam truac, sau dang cao d'finden hi~n Tuang trilm tfch Holocen vung tri6u cua song B~ch Dfing chu yeu la bai lily s6 v~t, tri~u thap va dilm lily yen bi~n, rat hiem cac lap mong xen k~p tuang duai tri~u [21,24] Di~u chUngto cac ngan bi~n nfim a vi trf cao hon hi~n chu yeu nang kien t~o tren ph~m vi cac dai nang TKT va KTHD Neu tach rieng, se co nhiing duang bi~u d6 dao dQngmt!c nuac tuong d6i co hlnh d~ng khac a cac dai kien t~o hi~n d~i sl;lt h~, nang di~u hoa va nang m~nh anh huang rat quan trQngcua chuy~n dQngkien t~o Bi~ud6 xay dt!Dgttr s6 li~u t~endai nang di~u hoa (nang rat yeu ho~c blnh Onkien t~o) se giln dao dQngmt!c nuac chan tlnh nhat Dao dQngmt!c nuac tuong d6i Holocen khu vt!c Hai Phong tuong tt! a d6ng bfingchau thOsong Tnrang Giang va dao dQng mt!c nuac a tInh day phu hQ'pva>ibi~u d6 cua Shepard Co nghla la, vao 5-6 nghln nam truac, bi~n tien ma rQng nhat Holocen, Ian sau vao II;lCdia nhung mt!c nuac tlnh Wc thap hon hi~n - 7m (hlnh 5) Ket qua nghien coo giln day a yen ba chau thOsong H6ng cling cho thay ket lu~n tuong tt! v6 dao dQng mt!c nuac bi~n tuong d6i Holocen [25] VI MOT s6 DANLI~U KHAo c6 VA qCH sir LIEN QUAN cac nhom cu dan van hoa Soi Nhl;ls6ng a moi tnrang II;lCdia, ma bi~n tien dang dang nhung a rat xa HQs6ng hang dQng tren II;lCdia nhu a D6ngDang,Ha Lung,HangDai ( Hoanh B6 - QuangNinh),ho~c tren cac dao nhu a HangDI;lC,Eo Bua, 37 a Ang Giii'a, Dong Oiu (Cat Ba, HJii Phong), hang Ma, Soi Nhl;!( Quang Ninh) Giap ~h~u (Vinh Cua Ll;!c);di v~t cua van hoa (?) bi chlm duai bi~n va bi tram tich bai lay bi~n phu len tren [5] Tu6i tuy~t doi etadu'1cxac dinh Mng phuang phap C14cho van hoa Soi Nhl;!ph6 bien 12-15 nghln nam truac, co tM keo dai tai 4-5 nghln nam truac [12] Trong cac tang van hoa chI) yeu phat hi~n du'1c cac lo~i oc nuac ngQt (Melania, Antimelania v.v.) rat hiem vo so, oc bi~n Nhom cu dan Tien H~ Long song ngoai trai tren cac bai bi~n, chan doi, suan mli nhu a Cai Beo (Cat Ba) chu yeu bAngdanh ca bi~n a cac cua song, vilng vinh kin song, du'1c dinh tu6i 5645:t 115 nam Co Ie, day la nhom cuoi cung cua mQt cQngdong da bi bi~n xam Ian Lap van hoa Cai Reo duai nAm'ngang mlJcbi~n trung blnh hi~n va thap han mlJc trieu cao 2m CMc cMn, phan bo cua cac di chi Tien H~ Long rQng rai han nhung ho~c bi ng~p duai nuac, ho~c bi xoa dau tich song xam thlJCa cac giai do~n sau SlJthay d6i 16'0cua moi truang c6 dia ly Hai Phong - H~Long co y nghia clJc ky to 16'0doi vai slJ phat trio~ncua cQng dong cu dan c6 thuQc van hoa H~ Long [6, 12, 14] Van hoa thuQch~u ky da mai, d~c trung bai bon, rlu mai toan than, bon co nac, rlu co vai va ban mai co ranh du'1cnM khao c6 hQcThl;!yDi~n Anderson J G phat hi~n Ian dau vao nam 1939 t~i mQtthem bi~n tren dao NgQcVirng No du'1c pMt hi~n a rat nhieu dia di~m cac moi truang khac nhu suan doi, doi cat, cac cat ven bi~n, cac them bi~n va ca hang dQng.Van hoa H~ Long xuat hi~n nhieu tren cac dao, ma dieu ki~n song hi~n cling rat kho khan, la mQttrong nhii'ngminh chUngcho qua trlnh ll;!Cdia hoa khu vlJcvao 3-4 nghln nam truac t~i Trang Kenh, thuQcvung clra song B~chDAng,nai dang chiu anh huang 16'0cua bi~n, da phat hi~n mQtdi chi khao c6 thuQc van hoa Phung Nguyen, co tu6i tuy~t doi khoang 3000-3400 nam truac [4] tuc la cung thai vai van hoa H~ Long T~i day, da tlm thay di tich lua nuac sam nhat tang van hoa Nghien cuu dia tang va c6 dia ly da chUngto dieu ki~n moi truang c6 phu hqp cho SlJphat tri~n kinh te nong nghi~p cay a Trang Kenh Trong do, chinh nai hi~n l~i khong phai la thu~n,I'1icho pMt tri~n nong nghi~p thuang bi m~n hoa, chua phen, ng~p 11;11 Cu dan van hoa H~ Long co Ie cling chu yeu song nha nong nghi~p Dqt bi~n Ian vao dau Holocen da d~y lui CUdan van hoa H~ Long khoi cac dao [20, 23] Cac mQthuyen da du'1cphat J:li~nakhu vlJcxa Phuang Nam (Dong Bi) va thon Vi~t Khe (Thuy Nguyen) MQthuyen du'1c chon tren bai lay ng~p nuac phan anh moi truang va cach song thich nghi cua GUdan ven dam lay nuac 1'1m~n Tu6i cua cac mQ thuyen du'1c xac dinh bang phuang pMp CI4 khoang 2000 - 2300 nam truac day, Ung vai thai gian cuoi cua dqt bi~n Ian dau Holocen mUQn,chuy~n sang bi~n lui vao giii'a Holocen mUQn.Cu dan Vi~t Khe c6 ngan cach ve thai gian vai cu dan Trang Kenh c6 qua mQtbi~n Ian vao dau Holocen mUQn 38 Khai dfiu giai doC;\nphat tri~n vung ba Bac BQmQt ngan nam qua ciing chinh la sl.1 ma dfiu cua Vuang trieu Ly troQg lich su Vi~t Nam Day ciing la thai di8m ghi nh~n chinh thuc vi~c xay dl.Jngh~ thong de ngan lfi a vung dong bang SOngHong, ma Iii ng~p lien quan den dang cao ml.1cbi~n nhu la mQt h~u qua quan trQng.Tai li~u SlIUt~p cua Ban Nghien coo Lich su Hai Phong cho thay nhiing di tich van hoa lien quan den thai Ly a Hai phong d6u co xu huang t~pJrung sat h~ de cat c6 thu 3, thap nhat h~ Thai nba Ly, dong bang song Hong a the dat cao rao nhat Holocen mUQn,co Ie la mQt thu~n l