NOTES A chemi cal i ndex of weat her- as i nf l uence of car bonat e wi t h var i abl e concent r at i ons and wi n d s o t r i n g e f f e c t o n g r a i n - s i z e d i s t r i b u t i o n i 7 ' ' 0 i , l e a d i n g t o t h e v a r i a t i on o f c h e mi c a l c o mp os i t i o n. On l y c o n s i d e r - i ng wi t ho ut e f f e c t o f wi nd i n g t he s e f a c t o r s c a n we t r u l y es t i ma t e t h e we a t h e r i n g n l o e s s a n d p a l e o s o l s . Re c e n t l y , we d e g r e e o f s i l i c a t e si s or t i ng: Fe / Mg r a t i osin s how t ha t Fe / Mg r a t i os i n t he a c i d- i ns ol ubl e pha s e s of l oe s s a n d p a l e os o l s c a n i n d i c a t e t he i n t e n s i t y o f we a t h e r t he a c i d- i ns ol ubl e phas e s o f i n g - p e d o g e n e s i s wi t h ou t t h e e f f e c t of wi n d s o ti r n g. l oe s s de pos i t s 1 Sampl e s a nd me t ho ds LI U Li an wen, CHEN Ju n, WANG Hon gt ao &CHEN Yang St a t e Ke y La b o r a t or y o f Mi n e r a l De p os i t Re s c a r e h Ge oc h e mi s t y, r Na n j i n g Un i v e r s i t y , Na n j i n g 21 0 09 3 t o of Su, iaci al C 黑u h i n a Abst r act Che mi c a l a na l y s i s o f a c i d- i ns o l ubl e f r a c t i on s i n l o e s s and pa l e o s o l s s ho ws t ha t c o nc e nt r a t i on s o f Fe a nd Mg we e r unde r c o nt ol r o f wi n d s o r t i ng a nd po s t - de po s i t i o na l we at he r i ng - pe do g e n e s i s . The f or me r c a us e d Fe a nd Mg c on- c e nt ra t e d i n t he f i ne r g r ai n- s i z e f r a ti c o ns , di s p l a y吨 s yn- c hr onous v a r i a t i o ns , whi l e t he l a t t e r ma de Fe an d Mg s e pa- r at e d, l e a di ng t o Fe et r a i n e d i n t he we at he r e d s e c t i on a nd Mg l e ac he d o ut . The ef r o e, r Fe / Mg r at i o s i n t he a c i d i ns o l ubl e f r a c t i on o f l o e s s a nd pa l e os o l s c a n e l i mi na t e t he e f f e c t o f wi nd s o r t i ng a nd s e r v e a s a n e x c e l l e nt pr ox y r e c or d o n i n- t e n s i t y o f we a t h e r i ng - pe do g e ne s i s . Ba s e d on c a l c u l a t i o n, l e a c hi ng pe ce r nt a g e o f Mg i n t he pa l e o s o l Sl f om r t he Luo- c hua n, Wi ng a nd Hua nx i a n s e c t i o ns i s 1 5%, 1 1 % a nd 2%, r e s p e c t i ve l y , a nd o n a v e r a g e 9% f or t he pa l e o s o l s S2 Sl y f om r t h e Luo c hu an s e c t i on, wi t h t he hi g he s t v a l ue a mo unt i ng t o 2 2% i n SS , s ug g e s t i ng t he s t r ong e s t we a t he r - i ng - pe do g e n e s i s Ke y wo r ds : l o e s s , pa l e o s o l , Fe ( Mg r at i o s , a c i d i n s o l ubl e pha s e s , c he mi c al we at he ri ng. Th e s a mpl e s we r e c o l l e c t e d ro f m t h e Lu o c h u a n s e e - L i o n ( 3 50 4 5' N,1 0 90 2 5' E) 一 An a l y t i c a l s a mp l e s i n c l u d e t h e Ma l a n Loe s s For ma t i on ( L, ) a nd t he Li s hi Loe s s For ma- t i on ( S, - L, 5 ) . Ea c h l a y e r c o l l e c t e d 1 -3 r e p r e s e n t a t i v e s a mp l e s . Be s i d e s t he Lu o c hu a n s e c t i o n , e v e y r 3s a mpl e s o f b o t h L, a n d S, we r e s e l e c t e d f r om t h e Xi f e n g ( 3 5 . 70 N, 1 07. 60 E) a nd Huan xi a n ( 36. 6` N, 1 07. 3` E) s e ct i ons , r e - s p e c t i v e l y . Ca r bo n a t e s we r e r e mov e d by a c i d l ea c h i ng be f o r e a na l ys i s . Ea c h s a mpl e r e a c t e d wi t h l mol / L a c et i c a c i d s ol ut i o n f or 6 h unde r cont i nua l a gi t a t i on, The n t he a c i d s o l ub l e a n d a c i d i n s o l u bl e f r a c t i o ns we r e s e p a r a t e d by c e n t r i f u g e. I n a d di t i o n, we s e l e c t e d o n e l o e s s s a mp l e a n d on e p a l e os o l s a mp l e rom f Lu o c h u a n t o e v a l u a t e t h e e f f e c t of gr a i n s i z e. Fi r s t , t he y we r e l e a c h ed by a c e t i c a c i d, a nd t he n t h e r e s i d u e s we r e d i v i d e d i n t o f i v e g r a i n - s i z e f r a c - t i on s ( i . e . >4 5 Pr o, 2 8 -4 5 pr o, 8 -28 pr o, 2 -8 pm a n d <2 pu t ) t h r ou g h we t - s i e v e , s e d i me n t a t i o n a n d c e n t r i - f uge . The c on ce nt r a t i ons of ma j o r a nd t r a ce e l e me nt s we e r de t e r mi n e d b y a n X- r a y f l u o r e s c e n c e me t h od ( XRF) i n t h e Ce n t e r of Mo d e m An a l ys e s , Na n j i n g Un i v e r s i t y . An ly a s e s wer e conduct ed under t he cont rol of st andar ds wi t h r el a- T h e l o e s s - pa l e o s o l s e q u e n c e s o n t h e Ch i n e s e Lo e s s Pl a t ea u pr ovi de a c on t i n uous pr oxy r e cor d on c l i ma t e c h a n g e s a n d c h e mi c a l we a t h e r i n g i n t h e p a s t 2 . 6 Ma l ' - s i Mu l t i pl e p r ox y i n d i c e s ha v e b e e n u s e d t o i n ve s t i g a t e t h e d e g r e e o f we a t h e r i n g a n d / o r p e d o g e n e t i c ewo r r ki n g of l o e s s d ur i n g p os t - a c c u mu l a t i o n, s u c h a s ma g n e t i c s u s c e p - t i b i l i t y , Rb / Sr r a t i o s , CI A v a l u e s a n d r a t i os of f r e e i r o n t o ot t al i r ony- s 1 . The s e i n di ca t or s r e v ea l t hat l oe s s ma t er i a l s u n d e r we n t c h e mi c a l we a t h e r i n g b e f or e a n d a te f r d e p o s i - t i on , c h a r a c t e r i z e d b y t h e l e a c h i n g a n d r e p r e c i pi t a t i o n o f c a r bona t es . As f or s i l i c a t e wea t he r i ng i n l oe s s an d pa l eo- s o l s , h owe v e r , c o n t r o v e r s y r e ma i n s . So me i n v e s t i g a t o r s p r o p os e t h a t s i l i c a t e mi n e r a l i n l oe s s a nd p a l e os o l s ha s bee n l i tl e a f f e c t e d by i n- s i t u we a t he r i ng a nd pe doge nes i s t h r o u g h s ud t i e s o n c l a y mi n e r l a a n d t h e s t r on g l y we a t h - l i ve s t a nda r d de vi a t i on of a na l ys es l es s t ha n 2% f or Fe a n d Mg. 2 Resul t s ( i)Con c e n t r a t i o ns o f Fe a n d Mg i n di f f e r e nt g r a i n - s i z e f r a c t i ons . As s hown i n f i g. I , c onc e nt r a t i ons of Fe a n d Mg a r e i n v e r s e l y p r o p o ti r o n a l t o g r a i n s i z e , wi t h hi g h e r v a l u e s i n t h e <2 I t m a n d 2-8 pm ra f c t i o ns . Ea r - t i e r r e s e a r c h " " h a s d e mo n s ra t t e d t h a t d u r i n g t r a n s p o ia r - t i on, q u a tz r a n d f e l ds pa r , r e s i s t a n t t o p h ys i c a l we a t h e r i n g, t end t o be e nr i ched i n t he c oar s er f r a ct i on whi l e f er r o- ma g n e s i a n mi n e r a l s l i k e c h l o r i t e , s us c e p t i b l e t o p hy s i c a l we a t h e r i n g , t e n d t o be e n r i c h e d i n t h e in f e r f r a c t i o n, l e a d - i n g t o d i f f e r e n t i a t i o n o f e l e me n t s i n g r a i n- s i z e f r a c t i o ns . Th i s i n t e r p r e t s t h e e n r i c h me n t o f Fe a n d Mg i n f ne i r f r a c - i on s . Fi g. 1 f u th r e r s h ows t h a t i n t h e s a me f r a c t i o n t h e Fe e r e d p a l e o s o l S 5 t s ' 0 J , wh i l e t h e o t h e ss r u g g e s t t h a t c h e mi c a l l a l t e r a t i on i n s i l i c a t e mi n e r a l s o c c u r s b a s e d o n a n a l y s e s o f c o n c e n t r a t i on o f t h e l o e s s s a mpl e i s c l os e t o t h a t o f p a - r a d i o a c t i v e i s o t op e s o f Be a n d U- Th a n d a q u e o u s c he mi s - l e os ol , whe r e a s Mg ha s a hi ghe r c onc e n t r a t i on i n l oe s s I r v i n t he Ye l l ow Ri ve r [ 7 , 1 0 1 t h a n i n p a l e os ol . Howev e r , t he s e r e s ul t s a r e mai nl y ba s e d on t he b ul k Al t h o u g h c o n c e n t r a t i o n s o f Fe a n d Mg a r e n o t a bl y f f e r e nt i n t h e g r a i n- s i z e f r a c t i o n s , t h e r a t i o s of Fe t o Mg s a mp l e s , t h e r e f o r e s o me p r o bl e ms i n e v i t a bl y o c c u r , s u c h di 1384 Sc i e nc e Bul l et i n Vol . 46 No. 1 6 Au gus t 2001 NOTES Fi g . 3 ( a ) i l l u s t r a t e s t h e r e l a t i o n s h i p b e t we e n F e a n d Mg con ce nt r at i ons i n a ci d- i ns ol ubl e f r a ct i ons of l oe s s 口 Loess uni t s f rom t he Luochuan s ect i on. I t can be obs er ved t hat a n e x c e l l e n t p os i t i v e c o r r e l a t i o n o c c u r s . Th e r e l a t i on s hi p c an be de ine f d as a l i n ea r e quat i on: . Pal ensnl ( 岁 }夕一 F e ( %) = 2 . 5 91 8 X Mg ( %) 一( ) . 1 9 4 5 ( R2 = 0 . 8 6 1 5 ) , ( 1 ) wh i c h r e f l e c t s s y n c hr on ou s va r i a t i o n o f c o n c e n t r a t i o n s of Fe a n d Mg i n l o e s s u n i t s . Pl o t t i n g r e s u l t s o f di f f e r e n t gr ai n- s i z e f r a c t i ons of t he l oe s s , we c an f i nd t ha t conc en- t r a t i on s o f Fe a n d Mg r u n c l o s e l y p a r a l l e l t o t he t r e n dl i n e f o u n d i n b u l k l o e s s s a mpl e s ( f i g. 3( b) ) , d e mon s t r a t i n g t h a t c o nc e n t r a t i o n s of Fe a n d Mg i n l o e s s we r e ma i n l y c o n - t r ol l e d by g r a i n - s i z e d i s t r i b ut i o n. Mo r e ov e r , c o n c e n t r a - l i o n s o f Fe a nd Mg i n Ma n l a n l o e s s ( L, ) f r o m t h e Xi f e n g a n d Hu a n xi a n s e c t i on s a r e a l s o pl o t t e d n e a r t h e t r e n dl i n e ( f i g. 3 ( c ) ) , i n d i c a t i n g a s i mi l a r v a r i a t i on o f t h e s e t wo e l e - me n t s i n l o e s s s a mpl e s f r o m d i fe r e n t s e c t i on s . The s yn c h r o n o us v a r i a t i o n o f Fe a n d Mg i n l o e s s uni t s r ef l e c t s t he b e ha vi or of f e r r o ma gne s i a n mi ne r a l s d u r i n g wi n d s o r t i n g. Mg - c o n t a i n i n g mi n e r a l s wi t h n o c a r b on a t e i n l o e s s a n d p a l e os ol s a r e a l l f e r r o ma g n e s i a n s i l i c a t e s , wh i c h a r e mo s t c h l o r i t e s ( i n c l u di n g v e r mi c u l i t e s ) a nd mi nor ho mbl ende , py r oxe ne a nd mi ca . Fe- cont a i ni ng mi n e r a l s i n l o e s s a r e f e r r o ma gn e s i a n mi n e r a l a nd f r e e i r o n s u c h a s o x i de a n d h y d r ox i d e o f i r o n. Du r i n g wi n d s o r t i n g , f r e e i r o n a s we l l a s f e r r o ma g n e s i a n s i l i c a t e t e nd s t o b e l8 ( 贷. ) ‘芝 12 0. 6 00 』 } 1 芭 抓乏、 之 c onc e nt r a t ed i n t he f i ne f r a c t i on, t he r ef or e c onc e nt r a t i ons > 45 28一 45 8一 28 2一 8 of Fe a n d Mg s how s ync hr onous va r i a t i on. < 2 Gr ai n s ue / 1 1 . Co n c e n ra t t i o n s o f F e a n d Mg a n d Fe / Mg r a t i os i n d i f f e r e n t s i z e f r a c t i ons o f l oe s s a n d pal e os ol g F r i a g i . n a r e s i mi l a r , r e f l e c t i n g t h e s i mi l a r be h a v i or o f t h e s e t wo e l e me nt s d u r i n g wi n d s o r t i n g nd a s h owi ng s y n c h r o n o us v a r i at i ons . Fu r t he r mor e, i n t he s a me ra f c t i on pa l e os ol ha s h i gh e r Fe / Mg r a t i os c o mp a r e d t o l o e s s ( f i g. 1 ) . (i i)Va r i a t i ons of c once nt r a t i ons of Fe an d Mg i n Luo c hua n s ec t i o n. Fi g. 2 s hows c onc e nt r a t i ons of Fe a n d Mg o f a c i d - i n s ol u b l e ph a s e s i n t h e Lu o c h u a n l o es s - p a l e o s o l s e q u e n c e . I t c a n be s e e n t ha t l owe r c o n c e n - t r a t i ons of Fe o c c ur i n t he l oe s s , wi t h av e r a ge of 3. 32% a n d l o we s t i n s a n d y l o e s s u n i t s肠 a n d _1 1 5 , a n d h i gh e r v a l ue s i n pa l e os ol s wi t h a ve r a ge of 3. 54%. The va r i a t i on p a te r n o f Mg i s c o n t r a y r t o Fe , wi t h hi g h v a l ue s i n l o e s s a n d l o w i n p a l e o s o l s . Th e a v e r a g e c on c e n t r a t i o n of Mg i s .36% 1 f or l oes s a nd 1 . 30% f or pa l e os ol s . ( i i ) S e pa r a t i o n b e t we e n Fe a n d Mg d u r i n g we a t h e r - i ng a nd pe d oge n es i s . As di s c us s e d above , wi n d s or ti n g r es ul t s i n en r i c hme nt of Fe a nd Mg i n t he f i ne r gr a i n- s i z e f r a c t i o n. Si n c e g r a i n s i z e i s mu c h in f e r i n pa l e o s ol s t h a n i n l o e s s , o n e mi g h t e x p e c t a n e nh a n c e me n t o f c o nc e n t r a t i o n s o f Fe a n d Mg i n p a l e os ol s . Ho we v e r , t h i s i s n ot t h e c a s e . As i l l u s ra t t e d i n f i g. 2, p a l e os o l s h a v e h i g h e r c o n c e n t r a - l i o n s o f Fe b ut l o we r c on c e n ra t t i o ns o f Mg c omp a r e d t o l o e s s . P l o t t e d t o g e t h e r wi t h r e s u l t s o f l o e s s ( ig. f 3 ( d ) ) , a l l da t a poi nt s of pa l e os ol s a r e a bove t he t r e ndl i ne, s ug ges t - i n g t h a t Mg, r e l a t i v e t o Fe , i s d e pl e t e d i n p a l e os o l s c o m- pa r e d t o l oes s . Fe r r oma gne s i a n s i l i c a t e s a r e s us c e pt i bl e t o ch emi ca l we a t h e r i ng i n s u r f i c i a l c o n d i t i o n s a n d ra t n s f o r me d t o c l a y mi ner a l s ( s uc h a s ve r mi cul i t e / c hl or i t e, v e r mi cul i t e a nd s me c t i t e ) , el r e a s i n g p a r t o f Fe a n d Mg f r om mi n e r a l l a t - t i c e S I 1 4 J . Th e s e r e l e a s e d - F e a n d Mg wi l l s e p a r a t e d u e t o t h e i r d i fe r e n t g e oc h e mi c a l b e h a v i o r i n s u r ic f i a l c o n d i - l i o n s . Mg i s a n a l k a l i n e - e a th r e l e me n t e a s y t o d i s s o l v e i n 3 Di scussi ons s oi l s ol ut i on an d i s c a r r i e d a wa y by s ur f a c e wa t e r wi t h ma l l a mo unt a ds o r be d by cl a y mi ner a l s , wher ea s Fe i s a (1)Re l a t i o n be t we e n Fe a n d Mg i n i n i t i a l a e ol i a n s dus t . Loes s i s a s i l t c ont ai ni ng a bunda nt c a r bona t e . I n t r a n s i t i o n a l e l e me n t t h a t i s p es r e r v e d i n s i t u d u e t o l o w o l u b i l i t y of ox i d e a n d hy dr o xi d e i n s oi l s ol u t i o n . Co m- l oe s s - p a l e o s o l s e q u e n c e s , l o e s s , f o r me d u n de r c o l d nd s a d y r c o n d i t i o ns du r i gl a c i a l p e r i o d s , h a s b e e n s u b j e c t t o pa r e d t o pa l e o e n v i r o nme n t o f l o e s s f o r ma t i o n, pa l e os ol s e v e l o p e d d u r i n g r e l a t i v e l y i n t e n s e s u mme r mo n s o o n a n d we a k c h e mi c a l we a t h e r i n g. Th e r e f o r e , l o e s s ha s t h e p o - d t ent i al t o r es er ve t he i nfor mat i on about r el at i on bet ween hi g h p r e c i p i t a t i o n. Th e r e f o r e l e a c hi n g e fe c t b y r a i nwa t e r was r ema r ka bl e, whi c h a f f e c t ed mor e f e r r oma gnes i an Fe nd a Mg rom f i ni t i a l a e ol i an dus t s . Chi nes e Sc i enc e Bul l et i n Vol . 46 No. 1 6 Augus t 2001 1385 NOTES St mt i g r a ph 5 Fe ( %) L 0 2 r 8 Fe / M只 Mg( %) S us c ep t i bi l i y t ( SI ) 32 3. 6 4 孰 蚝 孰 L民 玩 熟 匕 lO 20 。 执 召 飞0 导 以 凡 乳 51 I -o 叭 孰 60 51, 与51:凡 编 70 80 Fi g. 2. Va ia r t i o ns of c on c e n ra t t i ons o f F e a n d Mg, F c / Mg r a i t os i n a c i d- i ns o l u b l e f r a c t i on s o f l oe s s a n d pa l e o s o l s f r om Lu o c h u a n , c omp a r e d wi t h ma g n e t i c s us c e p ib t i l i t y s i gn a l 3R 40 护2. 5 91 8 x-0 . 1 945 , Xi f e ng 37 ( 岁 },」 3. 4 口 Hua nxi a n . 3. 0 3! 口 口 ( a) 2凡 !l M 1 g . 3 ( % ) ( c) 26 12 I5 14 Mg ( %) 4. 0 、 ‘ ,尸 L L 门 、 4 I. ( 罗 )‘ 」 ( 荞 )。舀 3. 1 (b ) ( d) 28 08 M g 1 . ( 6 , / . ) 2. 4 11 13 !5 Mg( %卜 Luo c hu a n l o e s s ; ( b ) d i f f e r e nt g r a i n - s i z e ra f c t i o ns ; ( c ) s a mpl e s f r o m F i g . 3. Re l a t i o n s h i p b e t we e n c o n c e n t r a io t ns o # Fe a n d Mg . ( a) Hu a n x i a n a n d Xi f e n g s e c t i o ns ; ( d) Lu o c h u a n p a l e o s ol s 1386 Chi nese Sci ence Vol . 46 No. 1 6 Au gu s t 2001 NOTES s i l i c a t e s t o b e d e c o mp os e d , r e s u l t i ng i n d e p l e t i o n of Mg i n pa l e os ol s "" As s umi n g t h a t l o e s s a n d p a l e o s o l s s ha r e t h e s a me A s d i s c u s s e d a b o v e , Fe a n d Mg i n l o e s s a n d pa l e o - s ol s l e n d t o b e e n r i c h e d i n t h e f i n e g r a i n- s i z e ra f c t i o n a n d d i s p l a y s y n c h r o no us v a r i a t i o n d u e t o wi n d s o r t i n g. Ho w- mat e r i a l s our c e, t he l i ne a r c or r el a t i on be t we e n c onc e nt r a - e v e r , d u r i n g - we a t he r i n g - p e d o g e n e s i s c o n t r o l l e d b y s u m- t mo n s o o n i n t e n s i t y , t h e t wo e l e me n t s wi l l s e pa r a t e t i on s o f F e a n d Mg f o u n d i n l o e s s c a n b e a pp l i e d t o p a - me t h F e r e ma i n i n g i n t h e s e c t i o n a n d Mg l e a c h e d o u t . l e o s o l . Mg c o n c e n ra t t i o ns of p a l e os ol s d u r i ng de p o s i t i o n wi c n a b e e s t i ma t ed by e q. ( 1 ) bas e d on Fe c once nt ra t i ons , Th e r e f o r e , Fe / Mg r a t i os i n t h e a c i d i ns ol u b l e f r a c t i o n o f nd a t h e n t he l e a c h i ng p e r c e n t a g e of Mg c a n b e c a l c u l a t e d l oes s an d pa l e os ol s c a n el i mi na t e t he efe c t of wi nd s or t- n g a n d s e ve r a s a n e x c e l l e n t p r o x y o n i n t e ns i t y o f by wh i c h we ca n di s c r i mi na t e t he deg r e e of c h emi c a l i we a t h e r i n g of f e r r o ma g ne s i a n s i l i c a t e s a n d t h e i n t e n s i y t o f we a t h e r i n g - p e d o g e n e s i s . we a t he r i n g - p e d o g e ne s i s o f p a l e os o l s . Th e c a l c u l a t e d Acknowl e dg e me n t s Th i s wor k wa s s u p p o te r d t h e Na t i on l a Ke y Ba s i c l e ac h i n g pe r c e n t a g e o f Mg i n t h e pa l e o s o l S1 f r om t h e Re s e a ch r P r o j e c t ( Gr a n t No . G1 9 9 9 0 4 3 4 0 0 ) a n d t h e Na t i o n l a Na t u r a l en c e Foundat i on of Chi na ( Gr ant No. 4 97253 07) Lu oh u a n , Xi f e ng nd a Hua n x i a n s e c t i o n s i s 1 5 %, 1 1 % nd Sci a 2% r e s p e c t i v e l y , i n a c c o r d wi t h t h e di fe r e n c e of mo d e m References cl i ma t e s i n t he山r e e l o ca l i t i e s . I n a ddi t i on, 9% 0 of Mg i n S. , Loes s a nd Envi onme r n t ( i n Chi nes e ) . Bei j i ng: Chi na 山e p a l e os o l s S } S1 4ha v e b e e n l e a c h e d o ut o n a v e r a g e , L O i r u e , T Press. 1985 Che n, 1 . , J i , J . F. , Qi u, G. e t al . , Ge oc he mi ca l s t udi e s on t he i nt e n- a n d t he h i g h e s t v a l u e a mo un t s t o 2 2% i n SS - , , s u g g e s t i n g s i y t o f c h e mi c l a we a t h e r i n g i n Lu o c h ua n l o e s s s e q u e n c e , Ch i n a , t he s t r o n g e s t we a t h e r i n g - pe d o g e n e s i s . Sci e nc e i n Chi na , Se r i es D, 1 998 ,41 ( 3 ) : 235 ( i i i ) Pa l e o c l i ma l i c i mpl i c a t i o ns o f Fe / Mg r a t i o s . Ga l l e t , S. , J a h n, B. M. , La n c e , B. V. L. e t a l . , Lo e s s g e o c he mi c a l As i l l u s ra t t e d i n f i g. 2 , F e / Mg r a t i os i n t he Lu o c h ua n a n d i t s i mp l i c a t i o n s f o r pa ni c l e o r i g i n a n d c omp os i t i o n o f t h e u p- p e r c on t i n e nt a l c us r t . Ea r t h a n d Pl a n e t a y r Sc i e n c e Le t t e r s . 1 9 98 s e c t i o n r e c o r d t h e a l t e r na t i o ns o f l o e s s nd a p a l e os o l s , wi t h 1 56:1 57 l ow v a l u e s i n l o e s s , hi g h i n p a l e o s o l s a n d h i g he s t i n t h e An , Z. S. , Li u, 工 S. , Lu ,丫,Th e l o n g - t e r m p a l e o mo n s o on v a r i a - s ron t g l y d e v e l o p e d s o i l S5 . Th i s d i s t r i b u t i o n p a t t e n r i s t i o n r e c or d e d b y t he l o e s s - p le a o s o l s e q ue n c e i n Ce n t r a l Ch i na , s i mi l a r t o t ha t o f ma g n e t i c s u s c e p t i b i l i y, t s u gg e s t i n g t ha t Qua t e na r y r I nt er na ion t al , 1 990, 78: 91 Ch e n, J . , An , Z. S. , Wa n g ,丫1 . e t a l . . Di s t r i b u t i o n o f Rb a n d Sr i n t he Fe / Mg r a t i o h a s p o t e n t i a l t o d i s c r i mi n a t e t h e we a t h e r - t he Lu o c h u a n l o e s s - p a l e o s ol s e qu e n c e o f Chi na d u in r g t h e l a s t i n g - p e d o g e n e s i s de g r e e o f l o e s s a n d p a l e o s o l s o f d i fe r e nt 8 0 0 k a: I mpl i c a i t on s f o r pa le o mo ns c o n va r i a t i o ns , S c i e n c e i n pe r i o ds . Ch i na , Se r i es D, 1 999, 42( 2) : 225 Mo r e o v e r , Fe / Mg r a t i o s c a n c l e a r l y i n d i c a t e t h e di f - Gu n, Z. T. , Li u, T. S. , Gui m, J . e t l. a , Hi g h re f q u e n c y pu l s e s of E as t As i a n mon s o o n c l i ma t e i n t h e l a s t t wo gl a c i a io t n s : l i n k wi t h f e r e n c e o f i nt e ns i y t o f we a t h e r i n g a n d p e d o g e n e s i s b e - t h e No r t h At la n t i c , Cl i ma t e Dy n a mi c s , 1 99 6 , 1 2: 7 01 t we e n l o e s s nd a p a l e os o l s i n d i fe r e n t l o c a l i t i e s . Fi g. 4 Go , Z. Y, Li u, T. S. , Gu n , Z. T. e t l. a , We a t he r i n g h i s t o r i e s o f s h o ws t ha t Fe / Mg r a t i os i n c r e a s e r e ma r k a bl y ro f m Chi n es e I es c s de pos i t ba s e d on ur a ni um a nd t h or i um s e r i e s n o- Hu a n x i n a a n d Xi f e n g t o Lu o c h u n. a Th e y a r e l o w i n c l i d e s a n d c o s mo g e n i c r 饱e , Ge o c h i m. Co s mo c h i n . Ac t a , 1 9 9 7 , 61 5221 Hu a n x i a n wi t h s l i g h t d i fe r e n c e b e t we e n l o e s s a n d p a l e o - Ha n, J. , Fyf e, W S. , Longs l afe , F. T. , Cl i ma t i c i mpl i c a t i ons of t h e s o l s , r e f l e c t i n g l o w p ec r i pi at t i o n a n d we a k we a t h e r - S 5 pa le os o l c omp l e x o n t he s o ut he nmos r t Ch i n e s e Lo e s s Pl a t e a u. i n g - p e d o g e n es i s i n Hu nx a i n, a wh e r e a s t h e Lu o hu a n s e c - Qu a t e na r y r Re s e a r c h, 1 9 98 , 5 0: 21 t i on d i s pl a y s hi g h e r Fe / Mg r a t i os nd a s t r i k i n g d i fe r e n c e J i , 1 . F . , Ch e n, J . , Lu , H 丫,Or i g i n o f i l l i t e i n t he l o e s s rom f t h e Lu o c hu a n a r e a , Loe s s Pl a t e a u , Ce n t r a l Chi n a . Cl a y Mi ne r a l s , b e t we e n l oe s s nd a pa l e o s ol , i n d i c a t i n g hi g h e r p r e c i p i t a t i o n 1 999, 34: 525 nd a mo e r i n t e n s e we a t h e ing r - p e do g e n e s i s . 29 一 一 -,.re se se s 一 ;- - Loess Ga i l l a r d e r , 1 . , Du p r 6 , B L u o va t , P . , Gl ob a l s i l i c a t e we a t h e r i n g a n d C02 c o ns ump io t n r a t e s d e d u c e d rom f t h e c h e mi s t y r of l a r g e r i ve r s , Chemi ca l Ge ol ogy, 1 999, 1 59: 3 Di ng , Z. L. , Li u, T. S. , Ru t t e r , NW I c e - v ol u me f o r c i n g of E as t As i a n wi nt e r mo n s oo n i n t h e pa s t 8 0 0, 0 0 0 y e a r s . Qua t e na r y r Re - 一 6 一 Pal ensol s e a r c h, 1 99 5, 44: 1 49 ( ) 一 1 出』翻芝 竺 Lu. H. Y. , An, Z. C. , Pa l e oc l i ma t i c s i g ni f i c a n c e o f g r a i n s i z e o f l o e s s - p a l a e os o l de p o s i t i n Ch i n e s e Loe s s Pl a t e a u , Sc i e n c e i n 2. 7 Chi na, Ser i es D. 1 998, 41 : 626 Ne s b i t t , H. W. , You ng , G. M. , Mc Le n n a n, S. M. e t a l . , Efe c t s o f c h e mi c a l we a t h e r i n g a n d s o r t i n g o n t h e p e t ig o e n e s i s of s i l i c l a s i t c s e d i me nt s , wi t h i mp l i c a t i o ns f o r p r ov e n a n c e s t u di e s , J o u na r l of 25 Ge o l o g y , 1 9 9 6, 1 0 4 ( 5) : 5 2 5 Ca mi c e l l i , S. , Mi r a b e l l a , A. . Ce c c h i n i , G. e t a L, We a t h e r i ng o f c hl o r i t e t o a l aw- c h a r g e e x p a n d a b l e mi n e r a l i n a Spo d os ol o n t h e Ap e n n i n e mou n t a i n s , I t a l y , Cl a y s a n d Cl a y Mi n e r a l s , 1 9 97, 4 5 ( 1 ) : 28 23 Hu a n xi a n Xi f e n g Lu oc h u a n Fi g. 4. Fe / Mg r a t i os i n l oes s and pa le os ol rom f di fe r e nt s ec t i ons Chi ne s e Sc i e nc e Bu l l et i n Vol . 46 No. 1 6 August 2001 J i . IF, Ch e n, 1 . , Li u , L. W. e t a l . . Ch e mi c a l we a t h e r i n g o f c h l o - r i t e a n d e n h a n c e me n t of ma g n e i t c s u s c e pt ib i l i t y i n Lu o c h u a n I ne s s s e c t i o n, Pr ogr es s of Na t u r a l Sc i e nc e ( i n Chi n es e ) , 1 999, 9: 61 9. ( Re ce i ve d J a n ua y r 1 2, 2001 ) 1387
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