Nghien CLPU- trao doi

Nghien CLPU- trao doi

c® P G S . T S . T r a n D u - c T h a n h - V i e n T a i n g u y e n v a M o i Tru'b'ng bien

M&DAU

C

at Ba Id q u i n dao, nhung Idn n h i t la dao Cat Ba cd dien tich 153 km^ (LD An, 1996), thupc huydn Cat Hai, Tp. Hai Phdng. Day la dao da voi Id'n n h i t phia Tay Vinh B l e Bg cung nhu ca Tdy Bien Ddng, la dao Id'n t h u 3 eua Viet Nam sau Phii quoc va Cai B l u , vai dinh cao

3 0 Bian Viet Nam - thang 05 - 2014

n h i t 331m, phia DB gidp vjnh Hg Long, phia TN va N giap viing bien phia ngoai VCS hinh pheu Bgch Dang. Trong dien tich 3 5 0 k n f cua ca viing (ridng qudn dao Cat Bd - 298 km^), cd td'i 392 hdn dao da vdi (ridng quan dao Cat Ba - 367 dap). Ndm ke sdt Vjnh Ha Long - mpt di san dia c h i t Thd gid'i, Quan dao Cat Ba cd nhO'ng dac diem vd gia tri dja c h i t n l i bat, mang tam

Vj tri cua ddo Cdt Ba

T h i gid'i - ngang Vjnh Ha Long, co nhung net t u a n g d i n g , dong th&i CO nhu'ng dgc diem khde bidt v6i Vjnh Ha Lcng ve dgc d i l m dia chat va dia mao.

1 . T6N6 QUAN D!A LY QUAN DAO CAT BA

1 . Vj tri dja ly va p h a m v i Di san Quan dap Cat Ba Di san ndm trong khung tog dp: 20° 35' 57.9"N - 20° 52' 48"N va 106° 53'

55" E - 107° 12' 55" E; cd tog dp trung tdm Id: 20° 44' 24"N vd 107°

03' 25" E (hinh 1); bao g I m khu D y trLF Sinh q u y i n Cdt Ba, Vud'n q u I c gia Cat Bd va quan dao Long Chdu, thudc huydn Cdt Hai, thanh p h i Hai Phdng, Viet Nam. Q u i n dao each thdnh p h i Hdi Phdng 45 km v l phfa Ddng va each thu dd Ha Ndi 150km v l phia D N ; phia Bdc giap Di san Thien nhidn T h i giai Vjnh Ha Long qua Lach Ngdn; phia Nam thdng vai Vjnh B I C Bp; phia Ddng gidp Di sdn Thidn nhien The gidi Vjnh Hg Long qua cu-a Igch Dau Xudi va Vinh Lan Ha; phia Tdy giap dao Cdt Hal qua Lgch Huyen Dien tich Dl san q u i n dao Cdt Bd la 33.670 ha, trong dd 13.478 ha dat t u nhien va 20.192 ha mat b i l n . Viing dgm khu di sancd dien tich Id 13.000 ha, trong do 3.984 ha dat t y nhidn va 9016 ha mat nud'c.

Di sdn bao gdm 4 vung:

- Viing I tong dipn tich la 1.615 ha (tga dp trung tdm 20° 50' 16"N - 106° 55'26"E), bao gom toan bd didn ti'ch cd 650 ha rirng ngdp man vd 965 ha dao va vung nud'c bao quanh

- Viing II Id khu v y c trung tam Di san rcng 17.350 ha (Tga do trung tam: 20° 47'57.45"N-107°0r36"E), c h i l m p h i n lan dien tich Khu Di san.

- V i i n g l l l gom todn bp viing bien tip Cdt Bd d i n Hdn Chen thugc q u i n ddo Long Chau rgng cd 8.208 ha (Toa dd trung tdm: 20°42'42"N - 1 o r 7 ' 5 0 " E )

Viing IV q u i n dao Long Chau vd'i 22 ddo nho va viing nud'c bao quanh d i n dp sau 27 m n u a c (ranh gid'i eo san hd phan bo), rdng 6.497 ha (tga dd trung tdm:

2'0°37'47.08"N - 107°09'27"E).

Trong do co cac ran san hd cdn t u a n g d i i tot.

2. Tong quan chung dja ly Q u i n dao Cat 8 ^ vd'i g i n 400 hon da vdi Id'n nho, cd dang thap k i l u Phong Linh va dgng chdp k i l u Phong Tiing. D a y la dja hinh karst nhi^t dd'i bj ngdp chim do bien tien Holocen. Quan dao rgng tren 300 k m ^ cao n h i t 322m, trong dd Cat Ba Id dao da vdi Id'n nhat d ven bd'

Tay B i l n Ddng. Tren dao, h l u h i t cdc dinh cd dp cao 100-260m, ddo Idn thud'ng cao 1 0 0 m - 2 5 0 m , dao nhd cao d u d i 100m vd cdc hdn r i t nhd thud'ng chi cao 20 - 50m.

Hoat ddng karst da tao ndn canh quan ddc ddo, n h i l u dgng dja hinh dgc bidt n h u hang ddng, mang da, chudng da, ede gieng, pheu karst va cdc thung lung karst phat t r i l n tren nen dut gay k i l n tgo nhu Trung Trang va Gia Ludn. Dinh vd sud'n cdc k h I i niii da voi la dia hinh dd tai meo s i c nhpn. Dao Cat Bd cd cac hang ddng noi t i i n g nhu Thien Long, Hoa C u a n g , Trung Trang va Quan Y v.v.. Trdn vach bd' dao, thidn nhidn cham khac nhung Idp da udn mem mgi, nhOng mai che va cac n g i n b i l n dang hdm I c h . An mdn hod hpc cua n u d c b i l n eiing vdi mai mdn do sdng vd ddng trieu tao ndn cdc hdm ech va cac hang luon xuydn thung eac khoi dd. Tren vach dd vdi cd ede n g i n n u d c b i l n co vd cdc Idp vd h l u hd bam. So lidu phan tieh C14 cho t h i y n g i n 4-6m tuoi 5-6 nghin nam t r u d c va n g i n 3-3,5m tuoi 2-3 nghin nam trudc. Qua trinh an mdn chdn vach lam tang tinh ki dj, dpe dap cua cac hdn ddo da vdi hinh chop va hinh thap.

Dao Cat Ba Id ddo da vdi Idn n h i t phfa Tdy Vjnh B l e Bg cung nhu ca Tay Bien Dong, Id ddo Idn thir 3 eua Vipt Nam sau Phu quoc va Cai B l u , vdi dinh cao nhat 322 m, phfa DB giap vjnh Ha Long, phfa TN va N giap viing bien phfa ngoai vung cua sdng hinh pheu Bgch Dang (hinh 2 va 3).

Dja hinh ddc trung d Cat Ba la cac vach d i e dipng, cac dinh, chdp cua cac k h I i nui da vdi h i l m trd- vd Idm chdm tai meo (hinh 4).

Cdc hang dgng trong cac khoi nui dd vdi.

Cdc thung lijng karst hep bj bao quan bdi day niii keo dai chu y l u theo p h u a n g TB - O N (Thung lung Trung Trang, Viet Hai v.v.) Cac tiing, ang an sdu vao vao b d dap (Tiing Rd, Tiing G l u , Tung Chang, Ang Vgm, Thdm v.v.) (hinh 5).

Cac bai trieu biin rOng Idn vd kha

bdng phang, trdn b l mat bai phdt t r i l n rtFng nggp man t u a i tot (bai Phil Long, bai Cai Vieng).

Cdc bai cat vd vdi sinh vgt va thdn, canh san hd (Cat Dua, Cdt Tien v.v....) (hinh 4).

Them san hd v i l n quanh chdn dao, Cac n g i n mai mdn, an mdn ciia n u d c bien v i l n quanh chdn dao.

Cac rgn san ho ngam.

Hd t h i n g kdnh lach trieu.

Nai cao n h i t la dinh Cao vgng (eao 322m), nam phia B l e ddo Cdt Ba, thudc xa Gia Lugn.

Nai thap nhat la dp sau 39m, n I m tren ludng lgch Van, thude V u d n Q u I c gia Cat Ba.

Viing bien vjnh Lan Ha sau n h i t tdi 18m dp d u g c tgi luc m y c n u d c b i l n trung binh.

Khi hgu vilng ddo thupc nhidt ddi ed mua Deng lanh. Nhipt dp khdng khi trung binh ndm 23-24''C, lugng mua 1 800 mm/nam vdi 120-130 ngdy mua, tap trung vao thang 7, 8 vd 9; do am khdng khi trung binh nam 82-85%, cao nhat 90-94%;

hudng gid thjnh hanh N- DN (vao thang 5 den 9) vd D- DB (thdng 10 d i n 4); toe dd gid trung binh 2,4 m/s. Hdng nam cd 1-2 can bao tac ddng tnpc t i l p .

Cung n h u cdc viing karst khac, mgng ludi thuy van trdn ddo Cdt Ba thua thdt va sudi t h u d n g cgn vdo mua khd. 0 ddy cd 4 suoi nhd cd n u d c chay t h u d n g xuydn, trong dd sudi T h u i n g Luong cd luu luang 5-10 i/s; s u l l Treo Cam cd luu lugng 7 1/s; ngoai ra edn suoi Hdi d Trung Trang, suoi Tien Dire d Viet Hat, luu lugng nhd. Mgt hd thien nhien trdn d a o - Ao £ c h , cd dipn tich 3 ha va cpt n u d c quanh ndm khodng 30 cm. Viing bien Cat Ba t u a n g d i i kin gid, thudc e h l do nhat trieu d i u , bien dd cao nhat 4,3 m. Sdng h u d n g DB vao mila Ddng, t h u d n g c l p 5. Miia he sdng mgnh han vdi h u d n g ON.

Cdt Ba cd 5 nhdm d i t chinh, gdm d i t feraiit nau dd trdn da vdi phan bo rgng rai, dat ehua; dat feraiit nau vang trdn da vdi xen p h i i n set, it chua; d i t feraiit trdng xam, vang nhgt, phdt trien trong cae thung lung da voi; nhdm d i t aluvi-deluvi;

Bi8n Viet Nam-thang 05-2014 3 1

ghien CIFU-trao doi

dat bai boi sdng bien.

Dao Cat Ba cd dac trung da dang sinh hpc cao vdi VQG va KDTSQ The gidi, cd nhidu kieu rCFng mua nhidt ddi xanh quanh nam (HST rimg tren nOi da vdi, rirng ngap nudc ngpt, RNM), con cd 1045,2 ha rimg nguyen sinh, vdi nhidu loai quy h i l m , trong dd vopc ddu trang la loai dae hiJu va bieu tugng cda dac. Viing t r i l u va bien ndng quanh dao cd khu he ddng thuc vat phong phu, ndm cgnh ngu trudng danh bat hai san ldn.

v l vi t h i dja kinh t l . Cat Ba la mdt trung tam du Ijch sinh thai dao - bien t i m c d Q u l e gia va Quoc t l . Phat huy va khai thdc t h i mgnh cCia VQG, DSTNTG, canh quan karst nhidt ddi v.v vdi nhilu san pham du Ijch ddc dao vd ed SLFC eanh tranh cao. Cat Ba, vdi vj tri gan bd va cua ngd cua thanh phd, hoan todn cd d l y dii d i l u kidn va Igi t h i d l nhanh chdng trd thanh mdt trung tam du lich sinh thai dao bien ldn, thu hut Odng dao khach du lich trong n u d c vd Qude t l . II. DAC D I £ M DIA C H A T K H U

vyc

1. Dja tang

Vide phan chia dja t i n g va tuoi t r i m tich cua chung cd nhiing khac nhau gii>a cae tac gia. 0 ddy, chiing tdi s u dung each phan chia cua Ngd Quang Toan va d i n g nghidp khi thanh lap t d bdn dd Dja chat Hdi Phdng ty le 1/50.000 nam 1995. Theo dd, thu t u tCr dudi ldn, khu vuc Cat Ba cd cae thanh tao dja c h i t sau:

1.1. He tang pho Han, tuoi Devon muon - Carbon som (D^ - C, ph)

He t i n g phd Han gdm chil y l u cac thdnh tgo t r i m tieh carbonate chipa phong phu hoa thgch Triing lo (Foraminifera), san hd va Tay Cudn (Brachiopoda).

Cdc thanh tgo cua he t i n g cd mat ea d Cat Ba, Thuy Nguydn va An Lao (Nui Voi), phan biet thanh 3 phu hd t i n g vdi tong be day 400 - 650 m.

- Phu he ting dLFai (D3 - C, ph1) gom eac da vdi phan Idp day, xen da vdi dang khdi, mau xam vd xdm den

Bi6n Viet Nam - thang 05 - 2014

Quan dao Cat Ba ~ Long Chau (nhin tip anh v& tinh Spot 2007)

- Phu he ting giCra ( D3 - C^ ph2) gdm cac dd vdi phdn Idp mau den, da vdi silic, set vdi phdn dai, da silic dang t h I u kinh mau den, phien set Thanh phan canxit cua da vdi dat tdi 97 - 98 %, set huu ca 2 - 3%, tuang t u cua da vdi silic la 65 - 6 8 % va 30 - 38%.

- Phy he ting tren (D3 - C^ ph3) gdm cdc da set bdt k i t mau xam,

dd silic mdu xam, xdm den, da vdi phan dai mau den.

Tgi Cat Ba, cdc da cua hg t i n g Id d khu vuc Viet Hal, Xudn Ddm va dai TN dao.

1.2. He tang Cat Ba, tuoi Carbon sam ( C, cb)

He t i n g Cat Ba gom cdc tanh tgo t r i m tfch carbon nguon g l c hod hpc vd sinh vat, phan bd chil y l u d khu v y c Cat Bd, han che han d Vjnh Ha Long, Bai TCP Long, Long Chau vd B l e Thuy Nguyen, ehua phong phii hod thgch TnJng Id, san hd, Tay Cudn va Hud b i l n (Crinoidea). Hd tang Cdt Bd ndm v l t chfnh hgp len he t i n g phd Han vd c h u y i n t i l p lidn tuc vdi he tang Quang Hanh d phia tren, cd b l day vdo khoang 400 - 450 m vd phan bipt thanh 2 phy he tang:

- Phu h0 tang dudi (C, cb,), day khoang 200 m, gdm da vdi phdn idp tLF mdng d i n day, mau xam den va den, xen cac Idp mdng silic vd set vdi, be ddy phdn Idp 0,2 - 1 , 0 m. Thanh p h i n khoang vat canxit tdi 96 - 1 0 0 % , thgch anh vd plagiocia 1 - 2 % vd set 2 - 3%.

- Phu h$ ting tren (C, cb^), day khodng 250 m, gom dd vdi dong nhat, xen dd vdi gia trirng ca, mau den va xam, phan Idp tip tnjng binh d i n ddy, c l u tao vi tinh.

Thanh phdn khoang vat canxit tdi 98 - 100%, cdn lgi la thgch anh.

Cd nai dd vdi bi dolomit hod vdi khodng vdt dolomit dat tdi 5 0 % 1.3. H§ tang Quang Hanh, tu6i Carbon muon - Perm (C^ - Pqh) Hg tang Quang Hanh g I m cac thanh tao carbonate phdn bo rdng rai d Vjnh Hg Long, Bai T i i Long, Quang Hanh, Deo But va khu v y c Cdt Ba. He t i n g ed bd ddy Idn, khoang 750 m vd d u g c phdn bidt thdnh 2 phy h$ t i n g :

- Phu h$ tang dudi, day khoang 400m, gom cdc dd vdi phan Idp day den dgng k h I i , mdu xam sang.

Thanh phan canxit cua da dgt tdi 100%, c l u tao vi tinh, nhung ddi cho bj dolomit hoa vdi lugng oxyt m a n h e d g t t d i 19%.

- Phu he tang tren ddy khoang 350m, g I m dd vdi phan Idp day den dgng khoi, cd xen cdc Idp

B6' d a o Cat Ba

mdng dd vdi silic, dd silic vdi d phan t h i p va da vdi cd c l u tao gia tn>ng ca d phan cap. Thanh p h i n canxit dat tdi 9 9 - 1 0 0 % , c l u tao vi tinh, thanh p h i n thach anh cd t h i tdi 1 % .

1.4. Cac thanh tao De tip (Q)

Thanh tao Od tir gom cdc t r i m tich bo rdi da nguon goc, phan bd rpng rai tren dap va day bien xung quanh. T r i m tich Be Tie co n h i t bat gap cd tuoi Pleistocene mupn va t h u t y tre d i n nhu sau:

- Tram tich D0 tir khong phan chia (Q)

T r i m tich D d T d khdng phdn chia trdn ddo Cdt Ba gom deluvi, proluvi va coluvi, thanh phan dg hgt lir mjn den thd va r i t thd (tang. khIi). Chiing l i p d l y eac dgng dia hinh karst co nhu: thung lung, pheu va hang karst. N h d do, tham thuc vat phat trien thanh rirng cung vdi qua trinh tao dat feraiit vdng dd, ddc bidt d cdc thung lung cham thoat n u d c .

- H$ ting VTnh Phuc, tudi Pleistocene mugn ( Q,^ vp)

He tang gom cdc t r i m tieh nguon gdc tiien, thanh phdn vyn thd g I m : cudi, sdi va chu ydu la sgn, cat, mau vdng ndu, chua nhidu mdnh vun than mdm va san hd, phdn bo d Ao Cdi (phia Tay ddo Cat Ba) tao nen them bien cao 10m t u a n g d i i d i l n hinh. Dgc bipt, tgi ddy cd cac di tich van hda khao co hau ky da mdi da d u g c khai qugt. Tram tich cCia he t i n g edn pho bien d thung lung Trung Trang, hidn Id viing canh tac chu y l u eua dao Cdt Bd.

- H0 ting Hai Hung, tudi Holocene sdm - giim (Q.^'^ hh)

He t i n g gdm eac tram tieh vun thd ngucn goc b i l n , chu y l u Id cat, sgn, sdi va cugi, chua phong phu manh vun san hd vd than mem, cd t h i gpi la t r i m tich vyn vd sinh vat. T r i m tfch cija he t i n g phan bo hgn che d Cdi Beo (DN Cat Ba) tgo nen them b i l n quy md nho, cao 4 - 5m.

Dgc biet Cdi Beo mdt di chi van hca n l i t i i n g , bap gpm cac idp vdn hda T i l n Hg Long va Hg Long.

- He tang Thai Binh, tudi Holocene muon (Q^^ Q tb)

Phan t r i m tich lye dia eua he t i n g nay da d u g c md td d phan tren ( t r i m tich D d t(y khdng phdn chia trdn dao). P h i n t r i m tich b i l n cua he t i n g ndy gom n h i l u t u d n g khde nhau:

Tram tich bai: T r i m tich bai (nguon goc sdng) r i t pho bien d khu v y e Cat Ba. Theo thdnh p h i n vgt c h i t va ngudn eung cap, ed t h i phdn bidt thanh 2 ioai:

Bien Viet Nam - thang 05-2014 3 3

Nghien CLPU- trao doi

- Cat thach anh luc nguyen, phdn b l han e h l d Dau Voi, D u g n g Gianh (Phil Long), Xudn Dam, H i i n Hap vd Ang Sdi.

- Cdt vdi vd sinh vdt d u g c cung c l p chu y l u tiF cac rgn san hd, phdn bo pho b i l n d ven b d v|nh Lan Hg, tao ndn cac bai noi t i i n g nhu: bai Tdy Tam, Cat Cd I va 11, Cat Q u y i n , Cat Difa vd Cat Cong Quan v v Bai cat vdi thudng chf ggp d cdc dao nui li^a bazan cd ran san hd vd cdc dao san hd giua dai d u a n g . Bai cdt vdi d Cat Ba, Long Chau vd Vjnh Hg Long - Bai TCP Long Id thdnh tao r i t dgc thii, khdng gap d u g c d nai ndo tgi phia Bac Vidt Nam. Theo thdnh phan dg hat, eat vdi vd sinh vat g I m ehu y l u hgt trung vdi dudng kinh tmng binh (Md) trong khoang 0,299 - 0,389mm d phan cao cda bdi, hgt nhd vdi Md trong khodng 0,163 - 0, 210mm d p h i n t h i p eua bai. 0 p h i n cao n h i t cua bdi (berm) ed the ggp cdt trung, cat Idn, sdi va cupi. Theo thanh p h i n vdt c h i t , vdi vd sinh vdt cd t h i dat tir tren 60 tdi trdn 90%, manh vyn da vdi tip 2 tdi 8,7%, cdn lgi Id thach anh vd mdt s i khoang vdt khach nhung h l u nhu khdng cd miin thyc v d t Tram tich r^n san ho. Rgn san hd la mdt dgng tich ty t r i m tieh sinh vat, chu y l u t u San hd tgo rgn, Thdn mem, Gidp xdc. Da gai, Hdi mien, Triing Id va Tao vdi. Tram tfch b d rdi tren mat ran chu ydu la cac thanh phan vd vdi hat thd nhu cat

tip vd cua nhieu loai sinh'vat va sdi, tham ehi Id cudi va tang chii y l u tip san hd eanh va dang khdi. Thanh p h i n vdt c h i t t r i m tich chu y l u Id carbonate, t h u d n g dgt trdn 90%, p h i n cdn lai chCi y l u Id manh vyn da vdi, dd vdi silic.

Rgn san hd trong khu v u c cd quy md nhd (trCF Long Chaut) t h u d n g khdng qua I h a . Theo k i l m ke sa bg, tong didn tich phan bo cac ran san hd khu v y c Cat Bd ( k l ea Hang Trai vd D i u Be) chi vao khodng 74ha, thudng phan b l d khoang dd sau 0,7 - 7, Om. Ran san hd vifa ia dang tfch tu, viFa la ngudn cung cap tram tich tgo ndn cdc bdi edt vdi l i l n k l . Trdn mgt cae rgn san hd chet thudng d u g c phu bdi Idp mdng bun sdt.

Trim tich bai triSu. Tram tfch bai t r i l u tich ty do dpng lye t r i l u tgp ra d viing t r i l u trong khodng do cao 0- 4,3m so vdi Om hai do, dug'c phdn biet thdnh 2 Ioal: bai trieu thap hinh thanh d u d i m y c trieu trung binh (2,06m/Om HD) vd bai tridu cao d phia tren m y c trieu trung binh.

T r i m tfch bai trieu thap gdm chO yeu la eat hat trung va hgt nhd l i n mdnh vyn vd sinh vdt, it mim hu-u ea vd dd u d t thap, d u d i 30%.

N g u g c Igi, t r i m tfch bai trieu cao g I m ehCi yeu la set, sdt bdt, lan manh vun rd sinh vgt, chu y l u Id thdn mem, gidu miin hCru ea vd tan tfch t h y c vat ngap mgn, dp u d t cao, CO the tdi tren 50%, dac bidt ed tich tu sulphur tong sd tdi 0,4 -

0,6%. Phan Idn t r i m tfch bai trieu cao n g u I n goc d i m l i y b i l n hien dai, tren dd cd phong phu thyc vSt nggp mgn, phdn bo chu y l u d phia Tay Cdt Bd (Phd Long), hgn che d phia B I C (Gia Ludn), phia TN (Xuan D d m , H i i n Hao vd Ang Sol).

d trdn mat, chiing thudng cd mdu nau hong, nau xam va d dudi 20cm hoac 60cm ed mdu xam xanh, xam den, giau mun hiru ea va t r i m tich t h y c vgt ngdp mgn va day cung la t i n g sinh phen t i i m tang.

Trim tich doi trieu, delta trieu. Duoc thdnh tao do ddng trieu rut, tgo nen cac dgng tfch ty n g l m , thudng xuit hidn d viing c u a LgchTrieu ldn n h u Igch Cua Vgn, cua cac tung dng (embayments and shelters) va Lgch Huyen. Thdnh phan co hoc cua chung gom chu y l u Id cat lan manh vyn vd sinh vgt va sdi.

Tram tich vung vmh. Pho biln cf vjnh Lan Ha va cac tung ang xung quanh, thanh p h i n chii yeu Id bCin set va set bdt, mdu xdm vd xam den, dp u d t cac. Btin set d ddy vjnh Lan ha cd hdm lugng cap hgt nho hen 0,05mm ed t h i dat tdi 70- 98%, thanh phan carbonate dgt toi 70%. (y c l p hat Idn han 0,05mm (biin bgt), thanh p h i n thach anh trong 7 - 30%, khoang vgt set 11 - 13%, vd sinh vgt 21 - 43%, rat it miin huu ca vd ddc bidt c6 ca manh vun than dd tuy ham lugng khdng dang ke.

Ang Tham, Cdt Ba