J ournal of China University o f Geosciences , Vol. 17 , No. 4 , p. 283 - 290 , December 2006 ISS N 1002 - 0705 Printed in China

Sanmenxia Loess and Paleoenvironmental Change

Zhao Zhizhong*(赵志中) Institute of Geomechanics , Chinese Academy of Geological Sciences , Beijing 100081 , China Jiang Fuchu (蒋复初) Institute of Geomechanics , Chinese Academy of Geological Sciences , Beijing 100081 , China ;Open Laboratory o f Lake Sediment and Env ironment , Chinese Academy o f Sciences , Nanj ing 210008 , China Wu Xihao (吴锡浩) Wang Shubing (王书兵) Qiao Yansong (乔彦松) Liu Ke (刘科) Institute of Geomechanics , Chinese Academy of Geological Sciences , Beijing 100081 , China Wang Sumin (王苏民) Open Laboratory o f Lake S ediment and Environment , Chinese Academy o f Sciences , Nanjing 210008 , China ; State K ey Laboratory o f Loess and Quaternary Geology , Chinese Academy o f Sciences , X i'an 710054 , China

ABSTRACT :The Caocun (曹村) loess profile of Zhangbianyuan (张汴 塬) is located at the southeast margin of the Loess Plateau, which is a typical representative of loess stratum in the Sanmenxia (三门

峡) area. In the 145 m thick profile , a loess-paleosol sequence occurs from L1 to L33 , underlain by a red

clay bed. The B /M boundary was recorded at the bottom of L7 , the Jaramillo event at S11 to S12 , the

Olduval event at L23 to L26 , and the M/G boundary at the bottom of L33 near the red clay. The magnetic susceptibility of the loess deposits, as well as the carbonate and granularity components, indicates that there have been many periodic paleoclimate changes , including a total of 13 cold events that each lasted more than 40 000 a. A high-resolution chronostratigraphic profile has been established using an age model according to grain characteristics. A clear correlation exists between records of the paleomonsoon in the Caocun loess succession and SPECMAP from 3 ×105 a B. P. to the present. The Caocun profile can act as a control site in the southeastern Loess Plateau. Its paleoenvironmental records relate to east- ern Asian paleomonsoon theory. KEY WORDS :Sanmenxia loess, magnetostratigraphy, paleomonsoon records, paleoenvironmental change.

INTRODUCTION 1989 ;Ding and Liu , 1989), mo re integrated strati- The Sanmenxia area is located at the SE margin g raphic profiles o f the loess-paleosol and its underly- of the Loess Plateau , w here a thick-layered loess de- ing red clay w ere co nstructed in SE of Zhangbian Vil- posit developed (Fig . 1). Previous research has al- lage in Shaanxian County. T he profiles displayed ready been car ried out o n some loess stratig raphy in sim ilar data , in reg ards to thickness and sequence o f the area (Teng , 1988 ;Xie and Jiang , 1987 ;Yue , strata , in co mparison to the ty pical pro file in the cen- 1985 , 1984), w hich concentrated on pe tro stratig ra- tral and southern pa rts of the Loess Plateau. Further phy and m agne tostratig raphy . Further environm ental investigatio n of the stratigraphic sequence of a ty pical investig ation has no t y et been pursued. After the g e- profile of the Lo ess Plateau might offe r an impor tant o logical survey (Zheng et al. , 1992 ;A n et al. , contro l profile of time-space change as rela ted to the m onsoon in eastern Asia (Xiao et al. , 1997). This This paper is supported b y the China Geological Su rvey ( No. paper considers the loess-paleoso l stratig raphy in the 200312300034) and the Ministry of Land and Resou rces of China (No. Sanm enxia area , paleoclim ate and paleoenvironment , 20010209). and provide s a com pariso n of the stratig raphy and pa- *C orresp on ding author :zhaozz@cags. net. cn leoenviro nmental change characteristics at Caocun. M anu scrip t received June 10 , 2006. The section studied includes L1 upw ard at the Cao cun M anu scrip t accepted S ep tember 25 , 2006. loess pro file , w hich w as used as a co nnection. The 284 Zhao Z hizho ng , Jiang F uchu , W u Xihao , W ang Shubing , Q iao Yanso ng , Liu K e and Wa ng Sumin

Figure 1. Location of the loess section in Sanmenxia. underlying red clay lay er profile w ill be discussed in a up the sequence of loess layer in the Sanmenx ia area. fo rthcoming paper. In orde r to investig ate the magneto stratig raphy of the profile , sam ples w ere sy stematically taken ev- MAGNETOSTRATIGRAPHY AND PALEOMON- ery 50 cm . To be sampled mo re densely at the polari- SOON RECORDS ty transform place , paleomagnetic samples o f 325- The Caocun loess pro file is lo cated east of Cao- cake in large size w ere colected all to gether. And cun Villag e , about 1 km SE of Zhangbianyuan , then tho se sample s we re cut to be directional cubes o f S haanxian Co unty , Henan Province. The profile is 2 cm long per side in the laboratory for the paleo mag- 760 m above sea level and its co ordinates are 34°38'N , netism experim ents in the Institute of Geo mechanics , 111°09'E (Xiao et al. , 1997). The profile's natural CAGS. The sy stem atical thermal dem ag netizatio n outcrop is caused by running w ater w hich creates a w as carried out based on per 50°interval during 2 ex- gully. The bottom of the loess-paleoso l sequence is periments. Upper Pliocene red clay . The averag e thickness of Residual mag netism w as measured after each de- the profile is 153 m , the loess lay er is 145 m thick mag netization using a Minispin ro tatio nal mag neto m- and the underlying red clay layer is at least 8 m thick eter , and then the data w ere sorted and analyzed and (the base could not be observed). a polarity histog ram w as draw n (Fig. 2). When According to the characteristics o f lithology and compared to the paleom agne tic time scale the paleo- magnetic susceptibility , 33-loess-unit-layer and 32- mag netic residual m agne tism in the Caocun loess pro- paleoso l-layer are dev elo ped in the profile. The pro- file indicated the presence of the Brunhes po sitive po- file from to p to base respectively is as follo w s :part larity zo ne (B), M atuyama neg ative po larity zone of M alan lo ess L1 (0 - 1. 5 m), Lishi loess (S1 - L15 ) (M), and the Gauss positive polarity zone (G). The (1. 5 - 87. 55 m ), Wucheng loess (S15 - L33 ) boundary of the B /M w as located at 49. 8 m , 20 cm (87. 55 - 145 m), and red clay layer (145 - 153 m) above the base o f L8 . The M /G bo undary w as loca- (Fig . 2). The petro stratig raphy has been described ted at 144. 8 m , 20 cm above the boundary betw een in detail by Xiao et al. (1997). The paleom ag netics , the loess and the red clay (Cande and Kent , 1995). magnetic susceptibility , g rain size and carbonate The tw o bo undaries in the loess w ere basically co n- samples w ere systematically analy zed. Through tests sistent w ith the positions of the po larity reversal and analy ses in the labo rato ry , the reco rd of magne- zo nes reco rded in the profiles from the central and to stratig raphy and the paleoenvironment at the Cao- southern areas of the Loess Plateau (Liu et al. , cun loess profile w as deduced , w hich can help to set 1988 ;H elle r and Liu , 1984), except that the po si- Sa nmenxia Lo ess and P aleoenviro nmental Change 285

Figure 2. Loess-paleosol sequence of the Caocun profile and magnetostratigraphy. tio ns we re a little low er. There we re an o bvio us Jara- Gongw ang ling , Wujiaji and Duanjiapo profiles (Yue millo positive po larity sub-zone (J) and an Olduval and Xue , 1996 ;Sun and Zhao , 1991 ;An , 1987). po sitive po larity sub-zo ne (O) in the Caocun profile. The O event at L 23 - L26 was po sitio ned a little hig her

The J event w as situated at the top o f S11 to the bot- than in the profile from the central area of the plat- to m of S15 w hich is co nsistent w ith J in the eau. In additio n , the “Lan” positive pola rity sub-zone 286 Zhao Z hizho ng , Jiang F uchu , W u Xihao , W ang Shubing , Q iao Yanso ng , Liu K e and Wa ng Sumin

w as lo cated in the middle o f L9 , a pre-J positive po- sults w ere also rectified , i. e. the carbo nate w as de- larity sub-zo ne w as lo cated at L15 , a Reunion positive ducted from the gene ral quantity . As a result the po larity sub-zo ne w as mainly located at L27 . character o f the curve w ave crest of the magnetic sus- There w ere well preserved polarity zones and po- ceptibility w as mo re obvio us , and further reflected larity sub-zo nes within the Caocun pro file. T he gen- the character of the m onsoon change ;the related eral character of magneto stratig raphy w as co nsistent study w ould be discussed in another paper in press. with the central area o f the Loess Plateau. Individual The granularity of the loess layer mig ht be used events we re inco nsistent w ith the g eneral pattern of as an indicato r o f a w inter mo nsoon. Its coarse com- the C retaceous , and might be related to the loess and ponent am ount w as ve ry w ell related w ith streng th o f paleoso l units division and /or regio nal stra tig raphic a w inter mo nsoon (Wu et al. , 1997 ;Xiao et al. , development ;and the pola rity zone (sub-zone) rev er- 1992). Grain size samples w ere taken every 5 cm in sal of the Caocun loess pro file w as basically found the Cao cun profile and measured using a g ranulome- within the loess layer. ter that w as m ade by the Institute o f Geo graphy and The susceptibility o f the loess-paleo so l sequence Lake , Chinese Academy of Science s , Nanjing. The reflected ho w much precipitatio n it had received , of- coarse grain content (>30 μm) w as gene rally 10 %- fered by paleo monso on to a certain deg ree. The refore 40 %, partial laye rs co uld reach 55 %, the change fre- a hig he r susceptibilty can be used as a pro xy fo r the quency w as higher than the curve o f susceptibility summer monso on in eastern A sia (Wu et al. , 1997 ; (Fig. 2). Acco rding to the content exhibition o f the An et al. , 1991a , b , 1989). The susceptibility w as >30 μm g rain g roup , the profile co uld be divided in- sampled by taking a measurement every 5 cm in the to tw o sub-sections as follow s :(1) the content of the

Caocun pro file. The measurements w ere m ade using coarse g rain above L15 w as higher , chang e range is al- an S US-942 susceptibility instrument that w as made so large r. There were obvious wave crest values re- by Nanjing No rmal University and Jiangsu Ocean & spectively at L 3 , L6 , L9 , L 15 , sho wing several stages Co ntinent Scientific & Technique Com pany . T he re- of a winter monso on w ith increased intensity ;(2) the -5 sults indica te that the susceptibility w as 25 ×10 - component of the coarse grain unde rneath L15 w as 310 ×10- 5 SI. low er , usually less than 30 %, the change rang e o f According to the curve created by plotting the content w as smaller , there were w ave crest value at measurem ents of susceptibility (Fig . 2), four m ajo r L27 and w ave valley value at S29 to the content o f chang es could be observed :(1) the sinuosity o f the coarse g rain in the w hole profile. In short , the g ran- susceptibility curve w as the greatest above S5 , reflec- ularity distribution character in the Cao cun profile ting violent changes to the m onsoo n climate ;(2) the sho wed an alternate status of the winter m onsoo n undulating range of susceptibility at L6 - S15 w as lar- from strong to w eak ;the content of coarse g rain g er , v alue of the susceptibility at L9 , L15 w as the could be a reflected character of the paleoclimate low est ;(3) the change of susceptibility at L16 - S27 changing fro m w eak to strong. w as smaller and undulate frequency of the suscepti- The change of carbonate content in the loe ss bility w as fast , reflecting a relatively smaller undu- mig ht reflect paleo clima te characte ristics during the lating climate rang e ;(4) the degree of susceptibility form ation process of the loess ;the ver tical undula- w as vastly different between L28 - L33 , reflecting a tion of carbo nate in the loess lay er co uld reflect a cy- relatively larger undulating clim ate range a t the m ain clic change o f climate fro m w arm-moist to dry-co ld , stage o f the loess depo sitio n (Xiao et al. , 1997). therefore it could act as a proxy to identify the sum- In g eneral , the susceptibility in the Caocun loess mer m onsoo n change in eastern Asia (An et al. , pro file w as hig he r than that recorded fo r the inte rio r 1991a , b ;Wen , 1989 ;Lu , 1981). of the Lo ess Plateau. This is co nsistent with the lo- Carbonate sam ples w ere taken every 5 cm in the catio n of Sanmemx ia in the southeast o f the Loess Caocun profile measured by the carbonate instrument Plateau. The reco rd of the changing characteristics of m ade by the Institute o f Geog raphy and Lake. The the monsoo n clim ate w as similar to the typical pro- measurement results indicate that the content of car- files in the interior of the Loess Plateau and in the bonate w ithin the paleosol w as lo we r , the carbo nate south. This indicates that the mo nsoon climate in content at S4 , S5 , S6 , S8 , S9 nearly reached zero , but eastern Asia w as co nsistent w ith the who le Loess in the loess the carbonate content w as higher slant-

Plateau since 2. 6 M a B. P. . The susceptibility re- ing ly ;and the content at L5 , L 6 , L7 , L9 reached Sa nmenxia Lo ess and P aleoenviro nmental Change 287 about 30 %(Fig . 2). The general change characters able features ;w hen building a time-scale , it should in the Caocun profile are as follow s :(1) change in be know n w hat foundatio n the m odel is based upon , the range o f the carbo nate co ntent above L4 w as ve ry and then it should be tested to built in time-scale in small , there w as a peak at L2 ;(2) the change at S4 - o rder to raise its precision.

S8 w as larg er ;(3) the carbonate co ntent at L 8 - S15 The paleo climate change from approxim ately 3. 0 w as lo wer , and the chang e in the range w as sm alle r ; M a has been recorded in detail at the Caocun profile. and (4) the chang e at L 16 - L33 w as larger. The loess-paleo sol sequence from approxim ately 2. 6 Through the distribution characte r of the car- M a reflected an obvious m onsoo n clim ate enviro n- bonate in the pro file , the w ave frequency of carbon- ment. It sho uld be sure tha t an ideal place has to be a te during the development pe riod of the loess w as offe red to investiga te the paleomo nsoon changes at fo und to be greater than that of susceptibility and the Cao cun profile fo r study o n paleo monsoo n o f the granularity change. This may indicate that the sho rt- Loess Plateau , therefore it should be fully impor tant tempo rary sum mer monso on w as streng thened during w o rk to set up a hig h reso lution time-scale of time- the dry-cold period to cause a response of increased stratig raphy fo r the Caocun loess profile. A ccording precipita tion in the stratum . to the calendar age of the dem arcatio n point on the o xyg en isotope boundary (M artinso n et al. , 1987) ESTABLISHMENT OF TIME-SCALE and the rev ersal ag e of the paleomag netic polarity Establishing a time-scale in the loess stratum is zo nes (Cande and Kent , 1995), the fo llow ing time- an important aspect of studying the loess stratig ra- contro lled points w ere selected :the bottom of L 1 w as phy , and also a fo undation fo r investigation into pa- 73. 9 ka B. P. , the B /M boundary w as at the base o f leoclimate chang e in the loess. Only by first establis- L8 being 780 ka B. P. , the top o f J event at S11 being hing a relative time-scale can change s in the regular 990 ka B. P. , the bo ttom of J event at the base of S12 pattern o f the paleo climate and its change m echanics being 1 070 ka B. P. , the top of O event at the m iddle be analy zed unde r the unifying time-scale. Subse- of L23 being 1 770 ka B. P. , the botto m of O event at quently , the finding s can be contrasted with the the middle-upper portion of L 26 being 1 950 ka B. P. , ocean-co ntinent , and developed into an investig ation and the M /G boundary at the base of L33 being 2 561 of g lobal paleoclim ate patterns. ka B. P. . Zoolites o nly offered the appro ximate tim e fo r Afte r ove rall analy sis o f the g ranularity data o f the lo ess stratum development ;but both 14 C and the Caocun pro file , it w as ascertained that the g ranu- thermo luminescent dating co ntributed to the loess larity component of >30 μm co uld be used as a prox y dating ;the magneto stratig raphy of the loess could be of the w inter m onsoo n in the Loess Plateau. Ado p- used to determine the appro ximate tim e period o f the ting the g ranularity ag e m odel to calculate the Cao cun stratig raphic forma tion ;as mentioned above , the lo- loess lay er , a boundary tim e of S1 - L33 w as o btained ess stratig raphic dating could no t far meet the target for each lay er , and a strong com pariso n w as made o n of precision to investigate the paleo climate change at the deep-sea o xyg en isotope stage (Rutter , 1992). In a high resolution , therefo re various models o f time- additio n , the time-scale co nstructed by the autho rs scale to the loess-paleo sol sequence w ere set up. Fo r w as tested , first to calculate the m odel-ag e at four- e xample , Liu (1985) suggested the “ accumulated positions , and then to co ntrast w ith a paleom ag netic do se mo del” ;Kukla e t al. (1990) considered that it dating age at four-positions w ith an er ro r less than w as in proportion to the m ultiplication amount , i. e. 5 %. As mentio ned above , it could be practical and the thickness of each layer m ultiplied by the suscepti- info rmative to set up a time scale of the Caocun loe ss bility o ver time , thus the “ susceptibility age m odel” stratum by using a g ranularity age m odel. w as set up ;Ding et al. (1991) based their m odel o n a periodicity study o f the paleoclim ate reco rd to set up DISCUSSION AND CONCLUSION the “ o rbit harmonious m ethod ” ;Porter and An The Caocun loess profile w as possessed w ell (1995) devised the “granularity age m odel” acco rding compared w ith typical pro files such as tho se of Luo- to the co rrelation betw een the time o f w ind dust dep- chuan , Xifeng , Baoji and Duanjiapo o n the Loe ss o sition and the granula rity no rms o f the winter m on- Plateau (Yue and Xue , 1996 ;Zheng et al. , 1992 ; soon. As mentioned earlier , tho se models o f time- An et al. , 1989 ;Ding and Liu , 1989 ;Liu et al. , scale of the loess-paleoso l sequence had distinguish- 1988) from lithostratigraphy and m ag netostratig ra- 288 Zhao Z hizho ng , Jiang F uchu , W u Xihao , W ang Shubing , Q iao Yanso ng , Liu K e and Wa ng Sumin phy. The distributio n of loess in China sho w s no w hich w as explained that the Sanmenxia area had ex- difference in concern to time and space , w hich is o ne perienced 33 cycles o f the climate chang ing from cold e xplanatio n for this scenario. Through investig ation to w arm since 2. 6 M a. Thus it can be seen from Ta- on the loess stratig raphy of the Sanmenxia area ble 1 that there were 7 occurrences of loess accum ula- (Wang et al. , 1999 ;Xiao et al. , 1997) com bining tions lasting ove r 40 ka since the last 1 Ma , and 13 development reco rd of paleo monsoo n and paleoenvir- occurrences since 2. 6 M a. These occurred at o nment o f w ind dust deposit loess stra tig raphy with a L2(48. 2 ka), L3 (56. 5 ka), L 4 (48. 1 ka), L 5 (70. 3 hig h reso lution at the last glacial stag e in M ang shan , ka), L6 (69. 0 ka), L7 (66. 5 ka), L9 (123. 3 ka), L13

Zhengzhou (Wu et al. , 1999 ;Jiang et al. , 1998), (82. 5 ka), L15 (71. 0 ka), L 22 (56. 7 ka), L27 (123. 7 the paleo monso on chang es could be effectively recov- ka), L30 (40. 6 ka), L 32(44. 8 ka). They possessed a ered w hen being pro cessed at the southeast of the Lo- ce rtain perio dicity to the irregularly display ed climate ess Plateau and its adjacent areas since approx imately events. The main tim es of climate chang e from 3. 0 M a. w arm-moist to dry-cold for the Caocun pro file o c- The Caocun loess profile includes 32 paleoso l curred at 2. 6 Ma (red clay /loess), 1. 37 Ma (bound- unit-bed representatives of inte rglacial stages and 33 ary o f L15 /S15 ), 0. 94 Ma (boundary of L9 /S9) and 0. loess unit-bed representativ es of glacial stages o nly 48 M a (boundary of L 5 /S5). on consideration of co mbinative paleoso l unit-beds ,

Table 1 Time-scale of the loess-paleosol sequence of the Caocun profile at Sanmenxia area Accumulated Sustained Boundary Ox yg en Accumulated Sustained Boundary O xy gen Stra ta Strata thickness (m) time (ka) ag e (ka B. P.) isoto pe stag e thickne ss (m) time (ka) ag e (ka B. P. ) iso to pe stag e

S1 5. 50 55. 9 73. 9 - 129. 8 5 S17 93. 85 48. 1 1 453. 0 - 1 501. 1 43

S2 12. 20 64. 6 178. 0 - 242. 6 7 S18 94. 90 11. 9 1 512. 4 - 1 524. 4 45

S3 18. 30 26. 7 299. 1 - 325. 8 9 S19 96. 40 21. 6 1 540. 0 - 1 561. 6 47

S4 24. 30 39. 4 373. 9 - 413. 3 11 S20 99. 10 47. 3 1 578. 8 - 1 626. 1 49

S5 34. 30 77. 7 483. 7 - 561. 3 13 - 15 S21 101. 75 18. 4 1 658. 6 - 1 677. 0 51

S6 42. 40 35. 8 630. 3 - 666. 1 17 S22 105. 55 21. 5 1 733. 7 - 1 755. 3 53

S7 47. 80 13. 8 732. 7 - 746. 4 19 S23 108. 35 33. 0 1 795. 2 - 1 828. 2 55

S8 52. 35 34. 4 781. 4 - 815. 8 21 S24 110. 55 32. 9 1 863. 2 - 1 896. 2 57

S9 64. 75 21. 3 939. 1 - 960. 4 25 - 27 S25 112. 20 28. 2 1 918. 4 - 1 946. 6 59

S10 66. 15 12. 4 967. 6 - 980. 0 29 S26 114. 90 48. 2 1 960. 5 - 2 008. 8 61

S11 69. 10 52. 1 989. 1 - 1 041. 2 31 S27 125. 40 71. 2 2 132. 5 - 2 203. 7

S12 72. 70 43. 5 1 068. 6 - 1 112. 1 33 S28 128. 25 26. 0 2 228. 6 - 2 254. 6

S13 78. 70 38. 0 1 194. 6 - 1 232. 6 35 S29 134. 00 103. 7 2 282. 6 - 2 386. 2

S14 82. 10 32. 4 1 266. 5 - 1 298. 9 37 S30 137. 20 17. 7 2 426. 8 - 2 444. 5

S15 89. 15 33. 0 1 369. 9 - 1 402. 9 39 S31 139. 40 17. 7 2 464. 0 - 2 481. 7

S16 91. 15 25. 6 1 418. 5 - 1 444. 1 41 S32 143. 40 31. 8 2 526. 5 - 2 558. 4

The character o f the paleom onsoo n , reflected by The Cao cun profile offers an ideal control profile the Caocun pro file , show ed attributes co mparable to to probe into the time-space distribution of the loe ss the data from the deep-sea ox ygen iso to pe study , the in China and paleo monso on change , w hich co ntained no rmal curve o f the m onsoo n record at the Caocun a substitutiv e reco rd o f the paleoclimate in detail pro file since the last 2nd g lacial stage is comparable since recent 2. 6 M a , w hich could be w ell com pared with the deep-sea o xy gen isotope curve since 300 ka w ith deep-sea deposits. Mo st reversals o f geo magnet- (Mar tinson et al. , 1987) (Fig . 3). Ox ygen iso to pe ic polarity occurred in the frigid g lacial stage. The stage 5(a - e), 6 , 7 , 8 , and susceptibility as a proxy frigid glacial stage possessed an overall identity to the summe r mo nsoon as w ell as co arse g ranularity develo pment-stage to the susceptibility and carbo nate com po nent as a prox y to the w inter monso on co rre- as a prox y o f summer m onsoo n and the com po nent o f spo nded bette r. This indica ted that the record o f con- coarse g rain as a pro xy o f w inter mo nsoon , show ing tinent w as much more sluggish than that of ocean. a periodicity character o f paleoclim ate change. It w as Sa nmenxia Lo ess and P aleoenviro nmental Change 289

Figure 3. Caocun loess profile comparison with deep-sea oxygen isotope since 300 ka. set up fo r the time-stratig raphic sequence in a high lo ng time scale as w ell as ocean-co ntinent correlatio n resolution to the Caocun loess-paleo so l depo sit by w ill need further investig ation. using a g ranularity age model, and paleoclim ate chang e under tim e co ntrol and co rrelation betw een o- ACKNOWLEDGMENT cean and continent w ere discussed. Reflecting pale- This research w as supported by the China Geo- o monso on change and its driving mechanics w ith a logical Survey (No. 200312300034) and the Ministry 290 Zhao Z hizho ng , Jiang F uchu , W u Xihao , W ang Shubing , Q iao Yanso ng , Liu K e and Wa ng Sumin of Land and Resources of China (No. 20010209). P orte r, S. C. , A n , Z. S. , 1995. Co rrelatio n between Climate Events in the No rth A tlantic and China during the Last REFERENCES CITED G lacia tion. N ature, 375:305 - 308 An , Z . S. , 1987. Lo ess-P aleo so l Sequences a nd Chro no lo gy at Rutter , N . W. , 1992. Lo ess in China and Global Chang e. L antian M an L ocalities :A spects of L oess Research. Chi- T ranslated by Ding , Z. L. . Quaternary Sciences , (1):2 na O cean P ress, Beijing. 192 - 203 (in Chinese) - 11 (in Chinese) An , Z . S. , Kukla , G . , Liu , T . S. , 1989. Lo ess Stra tig raphy Sun, J. Z . , Zhao , J. B. , 1991. Quaterna ry of L oess P lateau in in L uo chuan. Quaternary Research , (2):155 - 168 China. Beijing Science and T echnolog y P ress, Beijing . 23 An , Z . S. , L iu , D. S. , Lu , Y . C. , e t al. , 1990. T he Long- - 26 (in Chinese) T erm Paleo mosoo n V ariatio n Reco rded by the L oess- T eng , Z. H. , 1988. T w o L oess P ro file s and T heir Strati- Paleosol Sequence in Central China. Quaternary Interna- g raphic Divisio n in the Western H enan. Stratigraphy tional , 7 /8 :91 - 95 Magazine , 12(4):290 - 297 (in Chinese with Eng lish An , Z . S. , Wu , X . H . , Wang , P . X. , et al. , 1991a. P ale- A bstract) omonsoo n in China since Recent 130 ka (Ⅰ):Paleomon- W ang , S. B. , Jiang , F . C. , W u, X. H . , 1999. P aleo mon- so on Reco rd. S cience in China (Series D), (10):1076 - soo n Ev ents from the Last G lacial Stag e in Sanmenxia A r- 1084 (in Chinese) ea to the Early of Holocene Epoch. Acta Geoscientica An , Z. S. , Kukla , G . J. , Po rter , S. C. , et al. , 1991b. Sinica , (4):433 - 437 (in Chinese with English A b- M ag netic Susceptibility Evidence of M o nso on Va riation stract) on the Lo ess Pla teau of Central China during the L ast We n, Q. Z. , 1989. G eochemistry of Loe ss in China. Science 130 000 Years. Quaternary Research , 36:29 - 36 P ress , Beijing . 143 - 146 (in Chinese) Cande , S. C. , Ke nt , D. V . , 1995. Revised Geo magnetic P o- W u, X. H . , A n , Z . S. , W ang , S. M . , 1997. Lo ess and Pal- larity T ime Scale for the Late Cretaceous and Cenozoic. eomo nsoo n. Earth S cience Frontiers , 4(1 - 2):77 - 78 J ournal of Geophy sical Research , 100(B4):6093 - 6095 (in Chinese with Eng lish A bstract) Ding , Z . L . , Liu , T . S. , 1989. P ro gresses of Lo ess Research W u, X. H. , Jiang , F . C. , Xiao , H . G . , e t a l. , 1999. in China (Part 1):Loess Stratig raphy . Quaternary Sci- M a ng shan Lo ess o f Zhongy uan and Tecto nic M ov ement ences , (1):24 - 35 (in Chinese with Eng lish A bstract) since Recent 200 ka as W ell a s Clima te Chang e. Science Ding , Z. L. , Yu , Z. W. , Liu , T . S. , 1991. T he New Dev el- in China (Series D), (1):75 - 81 (in Chinese) opme nt of Loe ss Studies in China (3):T ime-Scale. Qua- Xiao , H. G . , Jiang , F. C. , Wu , X. H. , et al. , 1997. Lo ess ternary Sciences , (4):336 - 341 (in Chinese with Eng- St ratig raphy of Sanmenxia A rea :L oess , the Ye llo w Riv- lish A bst ract) er and the Y ellow Rive r Culture. Y ellow Rive r Hy draulic Heller , F. , Liu , T . S. , 1984. M ag netism of Chine se L oess P ublishing H ouse , Zheng zho u. 1 - 7 (in Chine se) Depo sits. Geophy s. Res. L ett. , 13:1169 - 1172 Xiao , J. L. , Zheng , H. B. , Zhao , H. , 1992. Va ria tion of Jiang , F . C. , Wu , X . H . , Sun , D. H . , e t al. , 1998. Loess W inter M onsoon Intensity on the Loe ss P la teau , Central Stra tig raphy of M ang shan, Zho ng yuan. J ournal of Geo- China during 130 000 Y ears :Ev idence from G rain Size mechanics , (4):12 - 18 (in Chine se w ith English Ab- Distributio n. Quaternary Research , 31:13 - 19 stract) Xie , F. C. , Jiang , Z. F . , 1987. T he Basic Character o f the Kukla , G . , A n, Z . S. , Liu , T . S. , 1990. Lo ess Stra tig raphy Loess in the Western He nan. Henan Geology , 5(3):42 in the M iddle of China :Loess , Q ua te rnary Geo lo gy a nd - 48 (in Chinese) Global Chang e (P art Ⅱ). Science P ress, Beijing . 115 - Y ue , L. P. , 1985. Study o n Paleomag netics of Shan County 133 and Xifeng Pro files: T he N ew Develo pment of Lo ess Liu, T . S. , 1985. L oess and Environment. Science P ress, Studies in China. Shaa nx i Peo ple's Publishing House , Beijing. 107 - 109 (in Chinese) Xi'an (in Chinese) Liu, X. M . , Liu, T . S. , Xu , T . C. , et al. , 1988. T he Chi- Y ue , L. P. , 1984. Study on Paleomag netics of the L oess P ro- nese Loess in Xifeng (Ⅰ):T he P rimary Study o n M ag ne- file of Zhangbianyuan, Shaan Co unty . J ournal of N orth- tostra tig raphy o f a Loe ss Profile in Xifeng A rea , G ansu west University , (4):79 (in Chinese w ith Eng lish A b- P rovince. Geophys. J . , 92:345 - 348 stract)

Lu , Y. C. , 1981. CaCO3 Content Cha ng e of L oess Stratig ra- Y ue , L. P. , X ue , X. X. , 1996. Paleo magnetism o f Loess in phy and Climate Cycle in P leisto cene. Scientia Geologica China. Beijing Science and T echnolog y P ress, Beijing . 38 S inica , (2):122 - 131 (in Chinese w ith Eng lish Ab- - 40 (in Chinese) stract) Zheng , H. B. , A n , Z . S. , Shaw , J. , et al. , 1992. M ag ne- M artinso n, D . G. , Pisia , N . G . , Hay s, J. D . , et al. , 1987. to stratig raphic Research of the Loe ss P rofile at the Duan- A ge Dating and the O rbita l T heo ry of the Ice A ges :De- jiabo :Lo ess, Q uaternary Geo lo gy and Global Change velo pment of a Hig h-Resolution 0 to 300 000-Year Chro- (Ⅲ). Science P ress, Beijing . 44 - 61 (in Chinese w ith no stratig raphy. Quaternary Research , (27):1 - 29 English A bstract)