K €t qua biroc dau nghien ciru t6c dQ lfutg dong va tu6i tram tich hien dai vung cira song B ach D fu1g bang phirong phap d6ng vi ph6ng xa 210pb va 137C S.. H6i nghi Khoa hoc Dia chdt bi
Trang 1V I~N B A N L A M K H O A H Q C vA C O N G N G H ~ V IeT N A M
V IE N D IA C H A T •• vA D IA V A T •• LV B IE N
V IE T N A M A C A D E M Y O F SC IE N C E A N D T E C H N O L O G Y
IN ST IT U T E O F M A R IN E G E O L O G Y A N D G E O PH Y SIC S
•
H Q I N G H f K H O A H Q C B fA clIA T B IE N T oA N ouoc L A N T H U H A l
PR O C E E D IN G S
T H E SE C O N D N A T IO N A L SC IE N T IFIC C O N FE R E N C E O N M A R IN E G E O L O G Y
H A N O I-H A LO N G , 10-12 O C TO B ER , 2013
Trang 214 T rin A nh T u~n, Phung V an Phach V ien dful chirng cir v~ dia m ao h6 tro 198 xac dinh ranh gioi vo luc dia - dai dirong tren B iSn D ong V iet N am
15 L e D inh N am , L e D uc A n, N guyin T h~ T i~p, Ph an D ong Ph a, va L e 207 Phuong, T rin X uan L vi, T rin A nh T uan, T rin H oang Y ~n, D uong T u~n
N goc, M Q t s6 d?c diSm dia m ao khu V \ICT ruong Sa va T ir C hinh - V iing M ay
16 B ili V an V U 'Q 'Ilg,T rin D uc T h~nh, D ~ng H oai N hon D ?c diSm hinh thai dia 219 hinh ran san ho quan dao T ruong Sa
17 T rin X uan L vi, N guyin T h~ T i~p, Ph an D ong Ph a, L e D inh N am , T rin 229
A nh T u~n, V ii L e Phuong, T rin H oang Y ~n, Pham V i~t H A ng, D uong
T u~n N goc, D ?c diem dia hinh dia m ao day bien N am T rung B Q
18 V ii V an Phai, D uong T u~n N goc, L U 'u T hanh C hung N hfm g bang chirng 243 dia m ao v~ S\I thay d6i m ire m roc bien tren dai bebien N am B Q trong giai dean
tir H olocen gifra d€n nay
19 V O T hjnh, Phan D ong Pha, N guyin X uan H uyen, V ii V an Ph ai, T ang Phuc 251
T u~n, L e D inh N am , T rin X uan L vi, T rin H oang Y ~n, va L e Phuong,
D uong T u~n N goc, C ac kiSu 00 bien khu V \ICPhu Y en - K hanh H oa va vfuI d~
du bao xu th€ bien dQ ng bo bien trong b6i canh m \IC m roc bien dang
20 Pham B a T rung D ac diem dia hinh day va trfun tich tfuIg m at vung bien ven 260
botinh B inh D inh,
21 N guyin D ang T uc, Phan T rong T rinh, B ili V an T hom , N guyin V an 271
H U 'O ng, N go V an L iem , V ~ cac them biSn va tu6i san he doc bo biSn K hanh
H oa - B inh T huan
22 V ii D uy V inh, B ui V an V U 'Q 'D g.A nh huang cua m Q t s6 y€u t6 khi nrong hai
van d€n bien dQ ng dia hinh day vung ven bo chau th6 Song H 6ng
23 V ii V an Phai, D uong T u~n N gQ c, L U 'u T hanh T rung, V ii L e Phuong, L e
D inh N am N ghien ciru dia m ao phuc vu quan Ifthong nhat doi bo bien
24 B ui V an V U 'Q 'Ilg,L iu Z hi Fei, T rin D uc T h~nh, T rin D inh L an, C hi-A n
H ub, T uo Shouting, D ~ng H oai N hon, N guyin V an Q uan, N guyin D ic V ~,
D inh V an H uy, N guyin D inh K hang K €t qua biroc dau nghien ciru t6c dQ lfutg dong va tu6i tram tich hien dai vung cira song B ach D fu1g bang phirong phap d6ng vi ph6ng xa 210pb va 137C S
25 N guyin T i~n H ai, Ivanova Y e.D , N guyin H tru Cu. D ?c diem m oi tnrong
tram tich akhu V \IC cira D a R ang, T uy H oa (Phu Y en) qua t~p m §:u16khoan
L k.D A 3
285
297
306
316
26 H oang T rung D u, T im Jennerjahn, A ndreas K unzm ann T ac dQ ng nguon 327 v~t ch~t song len lang dong trfun tich va y€u t6 sinh dia h6a vung bien ven bo
vinh N ha T rang - K hanh H oa
27 N guyin T rung T hanh, Phung V an Phach, L e D uc A nh, Pham T u~n A nh, 342
H oang V an L ong, Pham Q uac H i~p D anh gia anh huang phan toa phu sa cua song M e C ong len them I\lC dia k€ c~ bang ham hrong t6ng cacbon htru
co (T O C ) va cacbonat trong tram tich
28 Phi T ruong T hanh, T rin T u~n D iing, N guy~n Q uang M inh, N guyin T h] H ai 354
H a, N guyin T h] D ung, T rin T h] H A ng M inh, T on V an Son T 6ng quan v~ nui lira bun,
6
l
Trang 3H6i nghi Khoa hoc Dia chdt biin toan quoc ldn tM IIzyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA
KET QuA BUOC DAu NGHIEN ciru TOC DQ LANG DQNG
VA TUOI TRAMZYXWVUTSRQPONMLKJIHGFEDCBA'r t c n HI¥N D~I vUNG CUA SONG B~CH DANG BANG
PHUONG PHAp DONG VI PHONG ~ 210Pb va 137Cs
IBili Van VU'c;mg, 2Liu Zhi Fei, ITdn Du'c Th~nh, ITdn Dinh Lan, 2Chi-An Hub,
2Tuo Shouting, ID~ng Hoai Nhon, INguy~n Van Quan, INguy~n D~c V~,
IDinh Van Huy, INguy~n Dinh Khang
"Vien Tai nguyen va Moi truong bidn - VAST
2 7ruc'mg Dai hoc D6ng tt.Thuong LKJIHGFEDCBA H a i, Trung Qu6c
E-mail: vuongbv@ imer.ac.vn
TOM TAT:
Vimg cua song Bach DJng la mot cua song hinh phlu 11m va quan trong thir 2 & Vi¢t
Nam (sau c u a song D6ng Nai), nai co cang Hai P h o n g va cang nutrc SQU Lach H u y e n trong
tuong lai Vimg cua song nay chica dung tai nguyen thien nhien da dang va phong p h u , lien
quan ddn din h¢ thong lach tri€u va cac h¢ sinh thai nhu rung ngtjp mdn, bdi trieu v v Trdm
tich va dia hinh (fling dong tram tich, sa b6i luong lach) vimg cua song bidn d6i manh co anh
huong ddn gia tri tai nguyen va cac hoat d6ng kinh ddgc biet la cang bidn Bai bao trinh bay
kit qua nghien C U u buac dau vi t6c d6 lling dong, tu6i tram tich hien dai cua tram tich vung
cua song Bach DJng T6c d6 !&ng dong tram tich nhdn duac tir mat clit 210 Pb va 137CS bien
d6ng tir 0,69-0,97 cm/ndm, kh6i IU(1ngtram tich tich tu tir 0,5198 ddn 0,8045 (g.cm- 2 yr- l ).
210 Pb duac sit dung cho tinh toan tu6i tram tich hien dai trong vong 100 ndm, 137CS dung dd
xac nhdn d6c ldp kdt qua tu6i tram tich nhdn duac tir 2l OPb.
D~TvANDE
Tang quan vin d~ nghien cuu
Vao nam 1963, Goldberg IAn dAu tien d~ xuat v~ sir mAt thang bang gifra 210Pb va
226Ra co th~ phuc vu xac dinh tu6i trAm tich hien dai, Ciing trong nam do, ong da ap dung
thanh cong phirong phap phong xa 210Pb co ban chu ky phan ra la 22 nam d~ xac dinh tu6i
tram tich cua cac tang bang aGreenland [14] D€n nay, phirong phap nay dll duoc ap dung va
ph6 bien rong rai d~ dinh tu6i, t6c dQ l~ng dong trAm tich cho cac thuy V\fC: h6 [17], [36], bi~n
[18], [29] va dAm pha [2] Ben canh do 137CSciing duoc sir dung d6ng hanh, kiem chirng dQc
l~p so voi 210Pb d~ tinh to an tuoi, t6c dQ lang dQng trAm tich K€t qua tinh toan v~ tu6i, t6c d9
l~ng dong tram tich la C ( J sa quan trong nghien ciru anh huang cua qua trinh tram tich den qua
trinh xoi lo; b6i tu, gia tang dQ due, C ( J ch~ v~n chuyen tram tich tic nguon d~n b6n [6], [10],
[11] va cac tac dQng toi cac h~ sinh thai, vi du nhu h~ sinh thai co bi~n va ran san ho
306 tu« ban Dja ehdt va Tai nguyen, Khodng san biin
Trang 4tu« ban Dia chat va Tai nguyen, LKJIHGFEDCBA K h o d n g san biinzyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA307
H9i nghi Khoa hoc Dia chat bidn toan qu6e tdn thU II
Vung cira song Bach D~ng (VCSBD) la mot cira song hinh ph@u IOn va quan trong thir
2 Vi~t Nam (sau cira song D6ng Nai), noi co cang Hai Phong va cangZYXWVUTSRQPONMLKJIHGFEDCBAm r o c sau Lach Huyen trong nrong lai Day la vung cira song chira dung tai nguyen thien nhien da dang va phong
phu lien quan den h~ thong lach tri~u va cac h~ sinh thai nhu nrng ngap man, bai trieu v.v
Trftm tich va dia hinh va (lang dong trftm tich, sa b6i luong lach) vung cira song bien d6i
manh co anh huang den gia tri tai nguyen va cac hoat dong kinh te d?c biet la cang bien, do
d6 thu hut m6i quan tam cua cac nha khoa hoc nhir: tien hoa chau th6, dong lire hoc, trftm tich
hoc, dia mao hoc, v~n chuyen trftm tich, Nghien ciru v~ tu6i, t6c dQ l~ng dong trftm tich hien
dai a vung cira song nay v~n chira duoc quan tam Bai viet nay cung dp dfr lieu, thao luan v~
tu6i va t6c dQ I~ng dong tram tich hien dai vung cira song Bach D~ng dira tren tinh toan nang
luong phong xa cua 210Pb va 137Cs elOPb, 137CsradionucIides) tai mot s6 cQt khoan 6ng ph6ng
trftm tich tftng mat
TAngMLKJIHGFEDCBA q u a n v~ di~u ki~n t v nhien vimg cua song Bach J)~ng
V ung cira song co c~u true mra kin, co quan dao Cat Ba chan phia dong bac, ban dao
D6 San chan phia tay nam va con co h~ dao cat Phu Long, Cat Ba, Dinh Vii chan ph fa bien a
dong nam Cac nhanh song chinh tren vung cira song la Yen Lap, Bach D~ng, C~m va Lach
Tray (hinh 1)
Dia hinh VCSBD da dang va phirc tap, g6m nhi~u kieu, dang dia hinh co nguon g6c
khac nhau va co th~ duoc chia thanh 4 nhorn: Dia hinh d6i va nui thap, d6ng bang khong ngap
trieu, d6ng bang ngap tri~u tv nhien va dia hinh bo ngftm - luong lach ngap mroc thirong
xuyen [32] H ~th6ng lach trieu phat tri~n day d?c va thuoc hai nhom Nhorn thir nh~t phat
tri~n ke thira nr nhfmg long song cii diroc mo rong va dao sau long nho xam nhap cua dong
tri~u b~ mat va day (Lach Huyen, Nam Trieu, Cai Trap v.v.) Chung rong toi 2-3 km, sau toi
10-15 m va keo ngam ra phia bi~n chuc km Chung bao va chia cac khu bai trieu thanh cac
dao biet I~p, rong toi chuc krrr' Nhom thir hai g6m nhieu cap, hinh thanh do heat dong cua
dong trieu tftng mat, Chung phan dt cac dao bai trieu thanh nhieu manh khong tach roi nhau
Cac bai trieu cao chiem 70% dien tich, dQ cao tuyet d6i 0-1 m [32]
Day la vung co che dQ nhat trieu di~n hinh voi hftu h~t s6 ngay trong thang la nh~t
trieu, dQ IOn tri~u cue dai 4 m, t6c dQ dong trieu trung binh 30-50 cm/s, cue dai toi 1 5 0 - 1 8 0
cm/s Dong tri~u thuan nghich, eIIip tri~u r~t dep Kh6i mroc VCSBD co ban IQ'va IQ'nhat vao
mua rmra, lo va IQ'man vao mua kho
Dong chay co thanh phan dong tri~u quyet dinh, nen co tinh thuan nghich trong ngay,
phu thuoc vao dia hinh bo, huong bo, luong lach va cira song Dong chay manh vao cac thang
6, 7, 12, 1, y~u vao cac thang 3, 4, 8, 9 va manh nhat khi mire mroc dao dong len-xuong
ngang qua mire trieu trung binh T6c dQ dong trong khoang r~t rQng tir 0,1-1,8 m/s, trung binh
10-30 cm/s T6c dQ dong chay xuong IOn hon dong chay len: Tai cira Nam Trieu, t6c dQ dong
chay xuong cue dai 90 cm/s, t6c dQ len cue dai la 60 cm/s
Do anh huang cua dia hinh, song bi~n n6i chung khong Ian dQ, cao trung binh
O,75m, tnr nhfmg dip bao, tftn xu~t lang s6ng dat khoang 20% Trong hftu h~t cac thang,
Trang 5H(Ji nghi Khoa h9C Dia chdt biin toan quoc ldn thii IIzyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA
dQ cao song Ion nhat thuong 2-3 m, song bao dat 4-5 m, C\l'C dl;ll'5,6 m Vao mua dong, tir
thang 9 d~n thang 2 nam sau, song co dQ cao trung binh tir 0,5-0,75 m, thinh hanh huang
dong voi tan xuat 34% va dong bac voi tan xuat 14% Vao mua he, tir thang 3 d~n thang 8,
dQ cao song trung binh 0,7-0,9 m, song thinh hanh huang dong namZYXWVUTSRQPONMLKJIHGFEDCBAv c i tan x u s t 27% va
huang nam voi tan xuat 22% Vao cac thang chuyen tiep 4 va 10, song huang dong va
dong nam iru the
I TAl LI~U vA PHUONG PHAp NGHIEN CUu
1.1 Tili Ii~u
Bai viSt sir dung 2 cQt khoan voi mil hieu HP08 va HP 1°LKJIHGFEDCBAa dQ sau Ian hrot la 24 m va
10m so voi 0 m hai d6 (HD) ChiSu dai cQt khoan HP08 la 65 em va HP 10 la 90 em Hai cQt
khoan diroc thu trong chuyen khao sat chung g if r a Vien Tai nguyen va Moi tnrong bien
(IMER), Vi~t Nam va Phong thi nghiem Trong di~m Quoc gia Dia chftt bi~n (SKLMG), Dai
hoc Tongji, Thuong Hai, Trung Quoc thang 5 nam 2011 (hinh 1)
~-== ===~~~~~~r.nnr~~~ -~~~~rr~7>rJ~~~'~
0 0 ·
0 0 " C H U G I A I
-s- @
D u o n g d 6 n g sou ( m )
V i t r i c o t k h o a n
o km 5 10
,/ ","s- )
4 0 '
Hinh 1: Sa a 6 vung cua song Bach DJng va vitri lJ khoan HP08 vaHP 10
1.2 Phuong phap
12.1 Phtin tich phong X{l bang tia phJ gama
Theo dQ sau, cQt khoan dircc chia thanh cac mfiu, m6i mfiu img voi 2 cm S6 mfiu nay
duoc phan tich 210Pb va 137Cs b~ng tia ph6 gama (Analysis of radionuc1ides by y
-308 tu« ban Dia chat vaTai nguyen, Khodng sdn biin
Trang 6t u « ponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA ban Dia chdl va Tal nguyen, san biinzyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA309
H9i nghi Khoa h9C Dia chdt biin toan qu6c ldn thu II
spectrometry), theo tieu chuAn 327 va 375 [30] cua Co quan Nang hrong Nguyen tir Quoc t~
(IAEA), s6 m&u d~m tren may do GMX Thai gian d~m m&u dao dl)ng nr vai gio d~n vai ngay
tai Vi~n Khoa hoc Trai Dit, Vi~n Han lam Sinica, Dai B~c, Dai Loan
1.2.2 Phuong phdp xdc dinlt tac d~ !ting d!Jng tram tich
T6c d9 l~ng dong trim tich (cm.yr') duoc tinh toan tir d6ng vi phong xa 210Pb va
137CSdutheo d9 sau (excess 210-Pb hay 210Pbex, excess 137-Cs hay 137CSex)trong lap trim
tich 137 -CSdu xam nhap vao trong trim tich do cac VI,1 thir vii khi hat nhan va sir c6 nha
may dien nguyen tir [6], [14], [15], [21], [28] Trong nghien ciru nay cac m&u trim tich
diroc phan tich 137Cs (voi thai gian d~m dai) va liy nam 1950 la thai gian diu tien xuit
hien 137CStren vung bien [6], [10], [11] T6c dl) l~ng dong trim tich tinh theo t6c dl) phan
ra cua 137Cs ky hieu la SCs-137tinh theoZYXWVUTSRQPONMLKJIHGFEDCBAc c n g thirc: SCs-137=Z/(To-1950). Trong do Z, la
137Cs sir xam nhap theo dl) sau, To la thai diem thu m&u T6c d9 l~ng dong trim tich tinh
theo t6c d9 phan ra cua 210Pb ky hieu la SPb-210diroc tinh theo cong thirc SPb-210= - A 1m,
voi "Ala h~ng s6 phan ra cua 210Pb (0.03114y-I)
1.2.3 Kllai luirng tram ticb tich tl}
Kh6i hrong l~ng dong trim tich/don vi dien tich (g crniyr') duoc tinh tir theo
210Pbdu tai dl) sau z bit ky cua lap trim tich eIOPbxs(z») [3]:
Ln21OPbxs(z)-Ln210Pbxs(o)=(-A210m-I)W. Trong do: Dan vi kh6i luong tich tu trim tich diroc tinh bang kh6i hrong trim
tich tich tu kho, co don vi tinh (g.crn") w la quan h~ vo'i thai gian lang dong trim tich va
duoc di€n ta bang cong thirc t=W.fl (f la hru luong tich tu trim tich g.cmi.yr')
In210Pbxs(z)co d6 thi ngiroc voi kh6i luong tich tu tren mot don vi dien tich; w: k~t qua cua
mat c~t 210Pb la tuyen tinh va goc d6c la: -"A21ofl
12.4. Mo hlnh tinh tugi tram tich
SiI dung 210Pb d~ xac dinh tu6i trim tich la mot phuong phap ph6 bi~n va quan
trong hien nay Dua vao d6ng vi phong xa cua 210Pb, co th~ xac dinh diroc tu6i trim tich
hien dai trong vong 150 nam Trong trim tich t6n tai 2 loai 210Pb: "supported 210Pb" diroc
san xuit tai ch6 boi qua trinh phan ra cua 226Ra va excess 210PbelOPbex) nhan diroc tir khi
quyen Y nghia d9 phong xa (activity) cua 210Pb pharr b6 theo d9 sau nhan duoc rieng do
qua trinh phan ra theo lu~t ham s6 mii (hoac tuyen tinh n~u chung ta ve sa d6 logarit s6 tu
nhien) Tuy nhien gia tri n~n phu thuoc hoac l~ng dong trim tich va 210Pb phan b6 d~n vi
tri xac dinh hoacbien d6i qua thai gian Do vay, hrong 210Pbex bang hrong 210Pb t6ng tnr
di luong 210Pb diroc san xuat tai ch6
Co 2 me hinh tinh toan cho 210Pb d~ xac dinh tu6i trim tich diroc dung ph6 bien do
hi: CRS (Constant Rate of Supply) va CIC (Constant Initial Concentration) [14] va tiep
tuc duoc phat trien boi [25] Tu6i trim tich diroc tinh bang me hinh CRS (constant rate of
210Pb supply) [25]:
t=l/s In {A (O)IA (x)}
Trang 7310LKJIHGFEDCBA t u « ponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA ban cMt va nguyen, san biin
H9i nghi Khoa h9C Dia chat biin toan qu6c tdn thu 11
Trong do: A(O) thS hien hrong 210Pb du tren m~t tram tich;
A(x) thS hien 210Pb dir tai dQ sau (x);
A la hang s6 phan ra cua 210Pb (0.03114i1);
t la thai gian l~ng dong tr~m tich (tuci, nam)
SU dung 137CSdS kiem tra dQc l~p voi nam 1950 la thai gian b~t d~u xu~t hien 137CS
trong tram tich thuy V\l"C
11.1 K~t qua
T6c dQ va khoi hrong tich tu tram tich duoc xac dinh tir phong xa 210Pb va 137CScho
gia tri nrong d6ng T6c dQ lang dong tram tich tai vi tri HP08 tir 0,82 cm/nam dSn 0,97
cm/nam, kh6i hrong tich tu/l cm2 la 0,8045 glcm2/nam va tuong irng tai cQt khoan HPI0 la
0,69 dSn 0,75 crn/nam va 0,5198 glcm2/nam (bang 1)
Bang 1: T6c tJ (J tcing dong trdm tich (em/nom); kh6i lu a n g tich t1;-l/di¢n tich g/cm2/niim)
CQt T8c dQ ling d(}ng tr~m tich (cm/nam) tir dAng vi phong Kh8i hreng tich
V oi 2 vi tri CQt khoan, can cu phan tich phong xa, tu6i tr~m tich cho cQt khoan duoc
xac dinh tir nam 1910 dSn 2011, khoang 100 nam (hinh 2)
11.2 Thao lu~n
IL2.J.D{ic iliim liing dong tram tich VCSBD
Tir kSt qua tinh toan t6c dQ tram tich cua 2 cQt khoan HP08 va HP 1°cho thay: t6c dQ l~ng
dong trAm tich tai VCSBD tang dAn theo huang ra biSn: Tai cQt khoan HPI0, t6c dQ l~ng dong
trung binh tinh theo phuong thing dirng nr 0,69 dSn 0,75 cm/narn va 0,5198 glcm2/nam, trong
vong 100 nam (nr nam 1910 dSn nam 2011) Tai vitri cot khoan HP08 0 dQ sau 24 m/OmHD co
t6c dQ i1lng dong tram tich trung binh theo phuong thing dirng tir 0,82 dSn 0,97 cm/nam, kh6i
hrong tich tu/I cm2 la 0,8045 glcm2/nam, trong vong 66 nam (bang 1, hinh 2)
KSt qua tren r~t phu hop voi d~c diem hinh thai - dQng lire va phan b6 tram tich tai
khu bo hien dai: Hai CQt khoan HP08 (0 dQ sau 24 m/OmHD) va HPI0 (0 dQ sau 10
m/OmHD) thuoc phu doi song bien dang cua doi suon bo ngam va doi song pha huy [12],
[22] Ben canh do, tai d c i nay heat dQng cua cac ySu t6 dong luc: Song, dong chay t6ng
hop (thuy trieu, chay ven bo, dong chay song) 6n dinh theo mua trong nam, khong chiu
anh huang cua cac ySu t6 thai tiSt b~t thuong (bao), va heat dQng cua cac ySu t6 dong lire
nay cang 6n dinh.khi dQ sau khu bo cang tang len V6i d~c diSm nay, nen su phan b6, lang
Trang 8H(Ji nghi Khoa hoc Dia eMt biin toan qu6e idn thU IIzyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA
dong tram tfch nrong d6i 6n dinh theo khong gian va thai gian Tuy nhien, dieu quan trong
hon ca la tai vi tri cQt mftu HP8, anh huang phu sa cua h~ thong Song Hfmg d~n vung ria
ngoai cua VCSBD Ian hon.MLKJIHGFEDCBA
C o r e H P 0 8ZYXWVUTSRQPONMLKJIHGFEDCBAm C s ( d p m / g ) " " P b ( d p m / g ) C o r e H P 1 0 " 'C s ( d p m ig ) 2 " 'P b ( d p m / g )
I ~ ~ 2011 0
~
+
+ '
+ 1990 15
++
~
++
~
+
1950 z:,
1945 ~65 0.
~
"
1920 1,~ 8 0 Ks:
H i n h 2: Tu6i tr6m tich theo LKJIHGFEDCBA e lf) SQU tai 2 c(Jt khoan HP08 v a HP 10
IL2 2 v J kit qua tac tl9liing d o n g va tuJi tram t ic h VCSBD
V~ t6c dQ I~ng dong tram tich: trong nghien CUunay, nhom tac gia moi chi xac dinh
duoc gia tri trung binh cua t6c dQ I~ng dong tram tich VCSBD D~ co diroc k~t qua chi ti~t v~
t6c dQ lang dong tram tich theo thai gian dn k~t hop su dung voi cac phirong phap khac nhir:
Phuong phap ky thuat huynh quang tia X d~ quet cQt khoan (X-ray fluorescence -XRF core
scaning), ky thuat nhi~u xa tia X (x-ray diffaction) d~ nghien ciru khoang v~t set va thanh
phan co h9C tram tich.
K~t qua tu6i tram tich co dQ chinh xac cao, voi chi~u dai cQt khoan xfrp xi 100 em da
co th~ xac dinh duoc tu6i lap tram tich trong yang 100 nam cho cac vung cira song va cac
thuy VI,fCyen bo la kha phu hop K~t qua nay kha tuong d6ng voi cac k~t qua nghien ciru khac
nhau cua cac tac giai tren Th~ gioi thuoc cac thuy VI,fCkhac nhau: H6 [34], vung cira song
Amazon [31]
So sanh t6c dQ I~ng dong tram tich VCSBD voi cac thuy vue khac: No cao hon h~ dfim
pha Tam Giang - cfiu Hai (0,31-0,60 cm/nam theo [2]), thfrp hon cira Ba Lat (0,70-3,00 cm/nam
theo [13], thfrp hon so v61 cac thuy VVCyen bo Malaysia (1,57-8,64 cm/nam theo [36])
Day la k~t qua nghien CUudang tin c~y diroc ki~m soat va lira chon ngay tir ban dfiu:
Cac cQt khoan duoc II,fUchon thu theo cac doi hinh thai - dQng lire theo quan di~m dia rnao bo
bien cua cac tac gia n6i tieng tren Th~ gioi [5], [26] va cac nghien CUuco ban cua cac tac gia
Tiiu ban Dia chat va Tai nguyen, Khodng san biin 311
Trang 9312ponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Tiiu ban Dia chatva Tai nguyen, Khodng san biin
H6i nghi Khoa h9C Dia cMt biin toan quoc I[m tM LKJIHGFEDCBA I f
trong mroc [12], [22) Cac mftu v~t diroc phan tich bang thi~t bi va phuong phap hi~n dai K~t
qua diroc tinh toan theo co s6 Iy thuyet hien dai va cac phuong trinh toan da duoc ki~m
nghiem va sir dung ph6 bien tren th~ gioi (nhir da d€ c~p 6 cac muc d~t v~n d€ va phan
phirong phap nghien ciru)
KETLU~N
Phuong phap nuclit phong xa 210Pbva 137Csda duoc ap dung danh gia t6c lang dong
va tu6i tram tich tai 2 cQt khoan VCSBD Trong vong vai chuc nam d~n 100 nam qua, t6c dQ
lang dong tr§.m tich trong vung tang d§.n ra phia bien: tir 0,69-0,75 cm/nam va khoi lirong tich
tu/I cm21a 0,5198 g/cm2/nam (tai cQt khoan HPIO) d~n 0,82-0,97 cm/nam va khoi luong tich
tu/l cm2la 0,8045 g/cm2/nam
T6c dQ I~ng dong tram tich VCSBD cao hon cac thuy V\ICyen tinh (h6, d§.m pha), thap
hon vung cira song chau th6 (song H6ng) K~t qua lang dong tram tich phan anh duoc kha
nang cung dp tram tich cho vung cira song hinh ph~u: Giau tr§.m tich hon mot s6 V\ICmroc W
nhien yen tlnh va ngheo tram tich hon vung cira song chau th6
Lai cam an: Nghien ciru nay duoc tai tro boi Ti~u Du an 5 -ZYXWVUTSRQPONMLKJIHGFEDCBAH o p tac nghien ciru giua Vien Tai nguyen va Moi tnrong bien (IMER), Vi~t Nam va Phong Thi nghiem Trong di~m
Quoc gia Dia ch~t bien, Dai hoc Tongji, Thirong Hai, Trung Quoc Nhom tac gia xin bay to
loi earn on chan thanh d~n 2 co so tren Nhom tac gia cling bay to loi earn an chan thanh d~n
Giao sir Chen-Feng You thuoc Phong thi nghiem Dia hoa d6ng vi, Trung tam nghien ciru h~
thong dQng hrc Trai D~t, Truong Dai h9C Cheng Kung, Dai Loan va TS Hoang Van Long,
Truong dai hoc Mo - Dia chat, Vi~t Nam da cung thao luan v€ phirong phap tinh toan tu6i
tram tich va d6ng vi phong xa
TAl LI¥U THAM KHAo
I Ali Arman Lubis, 2004 Constant rate of supply (CRS) model for determing the sediment
accumulation rate in the coastal area using 210Pb.Coastal Development, pp 9-18
2 Albertazzi., Bellucci L.G et aI, 2007 210Pb and 137Csin sediment of Central Vietnam
coastal lagoons: Tentitive assessment of acculation rate Marine Science and Technology
Supplement 1, pp 73-81
3 B.S Shukla, 1989 An evaluation of the CIC Model of 210PbDating of Sediment Eviron
Geol Water Sci, Vol 14, No.1, pp 73-76 Springer-Verlag New York Inc
4 Bergan T.D., 2002 Radioactive fallout in Norway from atmoshperic nuclear weapons
tests [J) Environment Radioactivity, 60, pp 189-208
5 Bird E., 2000 Coastal geomorphilogy An introduction John Wilet and sons LTD
Chichester-New York, pp 1-322
6 Chih-An Huh et aI., 2011 Modern «100 years) sedimentation in the Taiwan Strait: Rates
and soure-to-sink pathways elucidayed from radionuclides and particle size distribution
Continental Shelf Research, 31 (2011), pp 47-63
Trang 10H6i nghi Khoa h9C Dia chat bien toan qu6c tdn tM 11zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA
7 Crozaz,LKJIHGFEDCBA G , et aI., 1964 Antarctic snow chronology withZYXWVUTSRQPONMLKJIHGFEDCBA2 1 oPb Geophysical Research, VoI.69, p 2597-2604
8 Do Minh Due et aI., 2007 Sediment distribution and transport at the nearshore zone of the
Red River delta, Northern Vietnam Asian Earth Sciences, 29 (2007), pp 558-565
9 Do Minh Due et aI., 2011 An analysis of coastal erosion in the tropical rapid accretion
delta of the Red River, Vietnam Asian Earth Sciences, x x x (2011) x x x - x x x (in press)
10 Huh, C.A et aI., 2006 Sedimentation in the Southern Okinawa Trough-rates, turbidites
and a sediment buget Mar GeoI., 231, pp 129-139
11 Huh, C.A et aI., 2009 Modern accumulation rates and a budget of sediment off the
Gaoping (Kaoping) River, SW Taiwan: A tital and flood dominated depositional
environment around a submarine canyon Mar Syst., 76, pp 405-416
12 Dinh Van Huy, 1996 f)~c di~m hinh thai - dQnglire khu bo hien dai Hai Phong Luan an
PTS Dia Iy - Dia chat, Truong Dai h9C Khoa h9C T\I nhien - DHQG Ha NQi, 127 trang
13 G.D Van Den Bergh et ai, 2007 Recent sedimentation and sediment accumulation rates
of the Ba Lat prodelta (Red River, Vietnam) Asian Earth Sciences, 29, pp 545-557
14 Goldber E.D., 1963 Geochronology with lead 210 In: Radioactive Dating [M], pp
12l-131 IAEA, Vienna
15 He Q., Walling D.E., et ai, 1996 Interpeting the 137Cs profiles observed in several small
lakes and reservoirs in southern England [ 1 ] Chemical Geology, 129, pp 115-131
16 Jay Stratton Noller et ai, 2000 Quanternary Geochronolgy methods and Applications
Lead-21 0 geochronology, pp 115-120
17 Krishnaswamy S et ai, 1971 Science Geochronology of lake sediments [ 1 ] Earth and
Planetary Letters, 11, pp 407-414
18 Koide M., Soutar A et ai, 1972 Marine geochronology with 210 Earth and Planetary
Science Letters, 14, pp 442-446
19 Milliman, J D et ai, 1983 World-wide delivery of river sediment to the oceans GeoI., 91,
pp 1-21
20 Milliman, J D., et ai, 1992 Geomorphic/tectonic control of sediment discharge to the
ocean: The importance of small mountainous rivers GeoI., 100, pp 525-544
21 Lu X., 2004 Application of the Weibull extrapolation to 137Cs geochronology in Tokyo
Bay and Ise Bay, Japan [1] Environmental Radioactivity, 73, pp 169-18
22 Nguyen Th~ Tiep, 1993 Hinh thai - dong lire ven b e Delta song Hong (Holocen hien dai)
Luan an PTS khoa h9C Dia Iy - Dia chat, 170 trang Truong Dai h9C T6ng hop Ha N9i
23 LJ Turner, L.D Delorme, 1995 Assesment of 2 1 0Pb data from Canadian lakes using the
CIC and CRS models Environmental Geology, 28 (2) September 1996 Springer-Verlag
pp.78-87
Ti€u ban Dia chat va Tai nguyen, Khoang sdn bien 313