Journal of Asian Earth Sciences 87 (2014) 157–164

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Journal of Asian Earth Sciences

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A luminescence dating study of the sediment stratigraphy of the LajiaRuins in the upper Yellow River valley, China

http://dx.doi.org/10.1016/j.jseaes.2014.02.0021367-9120/� 2014 Elsevier Ltd. All rights reserved.

⇑ Corresponding author. Tel.: +86 29 85310525; fax: +86 29 85310495.E-mail address: cchuang@snnu.edu.cn (C.C. Huang).

Yuzhu Zhang, Chun Chang Huang ⇑, Jiangli Pang, Yali Zhou, Xiaochun Zha, Longsheng Wang, Liang Zhou,Yongqiang Guo, Leibin WangDepartment of Geography, Shaanxi Normal University, Xi’an, Shaanxi 710062, PR China

a r t i c l e i n f o a b s t r a c t

Article history:Received 20 August 2013Received in revised form 22 January 2014Accepted 7 February 2014Available online 26 February 2014

Keywords:Yellow RiverGuanting BasinLajia RuinsQijia CultureOSL

Pedo-sedimentological fieldwork were carried out in the Lajia Ruins within the Guanting Basin along theupper Yellow River valley. In the eolian loess-soil sections on the second river terrace in the Lajia Ruins,we find that the land of the Qijia Culture (4.20–3.95 ka BP) are fractured by several sets of earthquakefissures. A conglomerated red clay covers the ground of the Qijia Culture and also fills in the earthquakefissures. The clay was deposited by enormous mudflows in association with catastrophic earthquakes andrainstorms. The aim of this study is to provide a luminescence chronology of the sediment stratigraphy ofthe Lajia Ruins. Eight samples were taken from an eolian loess-soil section (Xialajia section) in the ruinsfor optically stimulated luminescence (OSL) dating. The OSL ages are in stratigraphic order and rangefrom (31.94 ± 1.99) ka to (0.76 ± 0.02) ka. Combined OSL and 14C ages with additional stratigraphic cor-relations, a chronological framework is established. We conclude that: (1) the second terrace of the upperpart of Yellow River formed 35.00 ka ago, which was followed by the accumulation of the eolian loess-soilsection; and (2) the eolian loess-soil section is composed of the Malan Loess of the late last glacial (MIS-2)and Holocene loess-soil sequences.

� 2014 Elsevier Ltd. All rights reserved.

1. Introduction dating (Aitken, 1998). In the last decade, the single-aliquot

The Lajia Ruins, situated on the second terrace of the GuantingBasin along the upper Yellow River, was a significant settlement ofthe Qijia Culture (4.20–3.95 ka BP) in Eastern and Central Asia(Fitzgerald-Huber, 1995, 2003; Ye, 2002; Xia et al., 2003; Lüet al., 2005). The excavation of the Lajia Ruins has revealedevidence of the human struggle for survival during catastrophes(Ye, 2002; Xia et al., 2003). Similar to Pompeii, it is a rare archae-ological site preserved by a natural disaster (Ye, 2002). Scholarshave long been committed to identifying the disasters thatoccurred in the Guangting Basin where an important settlementof the Qijia Culture was devastated (Xia et al., 2003; Tarasov andWanger, 2005; Qian, 2007; Wu et al., 2009). Unfortunately, untilnow there has not been a detailed study of the chronologicalframework of the sediment stratigraphy of the Lajia Ruins.

Optically stimulated luminescence (OSL) dating has been usedextensively to establish the sediment burial ages that span thetimescale of the last glacial-interglacial cycle (Prescott andRobertson, 1997; Aitken, 1998; Zhou et al., 2009; Lai, 2010a; Laiet al., 2010b). Loess is an eolian sediment that is ideal for OSL

regeneration-dose (SAR) protocol (Murray and Wintle, 2000) hasbeen successfully applied to quartz grains from Chinese loess(Lai, 2010a; Lai et al., 2010b; Zhou and Shackleton, 2001).

Pedo-sedimentological fieldwork were carried out at the LajiaRuins in the Guanting Basin along the upper Yellow River valley.An eolian loess-soil section (Xialajia section, XLJ) was identified onthe second river terrace of the ruins. In this section, a layer of con-glomerated red clay has covered the ground of the Qijia Cultureand is intercalated with the mid-Holocene paleosol (S0). We alsodiscovered several sets of earthquake fissures that had brokenthrough the ground at the Lajia Ruins and were filled with the con-glomerated red clay, where various human remains, including pot-tery shards, burnt earth, ash, charcoal, stones and earth clods, werealso trapped. We therefore selected the Xialajia section for detailedstudy. Using OSL dating, Quaternary geomorphology, sedimentol-ogy and environmental archaeology, we construct the chronologicalframework of the eolian loess-soil stratigraphy of the Lajia Ruins.

2. Geographical setting

The Guanting Basin, a ca. 50 km2 basin in the upper Yellow Riv-er valley, is located in Minhe county, Qinghai province, China(Fig. 1A and B). The region is semi-arid and sub-arid with a

158 Y. Zhang et al. / Journal of Asian Earth Sciences 87 (2014) 157–164

monsoonal climate (Huang et al., 2013) and a mean annual tem-perature, rainfall and evaporation of 8–9 �C, 250–400 mm and2000–2100 mm, respectively.

The fluvial plain of the Yellow River within the Guanting Basinconsists of several eolian loess-blanketed river terraces found atelevations of 1760–1860 m asl. The second river terrace (TII), rest-ing on the Pliocene red clay, is a pedestal terrace (Huang et al.,2013). The upper and low parts of the river terrace consist of eolianloess-soil and fluvial deposits. The river terrace largely follows theoriginal landscape and inclines from north to south because of theslope of the alluvial fan. The terrace is approximately 1–2 km wideon the northern riverbank and 1 km wide in the south. The frontsection of the second terrace is located approximately 30–35 mabove the modern Yellow River water table.

Fig. 1. (A) Site map showing the location of the Yellow River and the Xialajia site. (B) Gooand the landscape features of the Guanting Basin. The area with the red mudflow depos

The thick loess-soil cover forms flat and fertile land on the sec-ond river terrace (Fig. 1B) that has been occupied and cultivatedextensively since the Neolithic (Yang et al., 2004). The Neolithicand Bronze Age sites, including those from the Majiayao Culture(Majiayao style, 5.30–4.80 ka BP), the Qijia Culture (4.20–3.60 ka BP), the Kayue Culture (3.60–2.60 ka BP) and the XindianCulture (3.40–2.60 ka BP) have been discovered in the GuantingBasin (Xie, 2002; Dong et al., 2012).

Accelerated erosion related to human activities has resulted inintensified mass wasting on the surrounding hillsides. Severaldry gullies or seasonal streams (such as Baojiagou, Lüjiagou, andGanggou gullies) that originated from the surrounding hillsidesdissect the second river terrace. Flash floods, mudflows and debrisflows occur frequently in the head waters of these tributary gullies

gle Earth satellite image showing the location of the Lajia Ruins and the Xialajia siteit is indicated by the dotted line circle.

Y. Zhang et al. / Journal of Asian Earth Sciences 87 (2014) 157–164 159

during summer rainstorms (Fig. 1B). Large alluvial fans formed atthe exits of the gullies onto the plain and at the confluences ofthe gullies joining the Yellow River. These confluences in the frontof the second river terrace often shift as a result of the formation ofalluvial fans. For example, the Lüjiagou gully near the Lajia Ruinshas diverted to the east to join the Ganggou gully and no longer di-rectly joins the Yellow River (Fig. 1B).

3. Sampling and dating methods

3.1. Sampling

A pedostratigraphically complete loess-soil section at the Xiala-jia site (XLJ, 35�5103700N, 102�4805300E, 1795 m asl) was chosen forthis study (Fig. 2). Based on the changes in colour, texture andstructure, we present pedostratigraphic subdivisions and descrip-tions for this section (Table 1).

The settlement of the Qijia Culture in the Lajia Ruins was datedto 4.20–3.95 ka BP by using 14C dating method on a large group ofcharcoal samples collected from the cultural layers of the LajiaRuins during archaeological excavations (Zhang et al., 2003,2005, 2009). It is thought that the prehistoric people of the QijiaCulture moved into the Guanting Basin in 4.20 ka BP. They builttheir settlement in the front section of the second terrace wheretwo tributary gullies join the Yellow River. In 3.95 ka BP, the com-munity disappeared when the settlement was suddenly devastatedby the conglomerated red clay that accompanied a major earth-quake. Based on our field investigations and sedimentological anal-ysis, the red clay is classified as the deposit of dense mudflows(Huang et al., 2013; Zhang et al., 2013).

Eight samples for OSL dating were collected from the MalanLoess, the transitional loess, the palaeosol and the modern soil inthe XLJ section. All OSL samples were taken by hammeringstainless steel tubes into cleaned vertical sections and immediately

Fig. 2. (A) Eolian loess-soil sections containing conglomerated red clay, under which theat the Xialajia site in the Guanting Basin along the upper Yellow River valley. (B and C) Hsite (Ye, 2002).

covering and sealing the tubes with tinfoil to avoid light exposure.OSL measurements and associated tests were carried out in the OSLlaboratory of Shaanxi Normal University, Shaanxi province.

3.2. Luminance sample preparation

OSL samples were uncovered under subdued red light in theOSL laboratory. The outer 2–3 cm were removed and the interiorused for further processing, including pretreatment with 10% HCl(to remove carbonates), 30% H2O2 (to remove organic material)and wet sieving to obtain the 40–63 lm grain fraction. The 40–63 lm grain fraction was etched by 40% HF for 40 min to removefeldspar grains, and then treated with 10% HCl to remove acid-soluble fluoride precipitates. The purity of quartz grains wasexamined by detecting the infrared-stimulated luminescence(IRSL) signal and the shape of the 110 �C TL peak (Mejdahly andChristiansen, 1994). Quartz grains were then mounted on the cen-tre (5 mm in diameter) of aluminum aliquots (9.7 mm diameter)with silicone oil.

Luminescence measurements were carried out on an automatedRisø TL/OSL-DA-20 reader (Lapp et al., 2009). Blue light(470 ± 30 nm, �50 mW cm�2) LED stimulation was used for thequartz grain OSL measurements. The OSL signal was detected withan EMI9235 QB15 photomultiplier tube with a 7 mm-thick HoyaU-340 glass filter. The reader is also equipped with a 90Sr/90Y betasource delivering 0.081 Gy s�1 and an IR laser diode (830 nm,�145 mW cm�2).

3.3. Equivalent dose determination

Equivalent dose (De) was determined using both the single-ali-quot regenerative-dose (SAR) protocol (Murray and Wintle, 2000)and a standardized growth curve (SGC) method (Roberts andDuller, 2004; Lai, 2006). For each sample, 6–12 aliquots were

ground are broken by earthquake fissures and filled with the conglomerated red clayuman remains of the Qijia Culture (4.20–3.95 ka BP) in the Lajia Ruins at the Xialajia

Table 1Pedostratigraphic descriptions of the eolian loess-soil section at the Xialajia site in the Guanting Basin along the upper Yellow River valley.

Stratigraphicsubdivisions

Depth (cm) Colour Texture Structure

Top soil (TS) 40–0 Orange(7.5YR6/6)

Silt Granular structure, porous, friable, some earthworm burrows and excrement, abundant well-rounded spherical pellets, some plant roots, 30–50 cm in thickness.

Recent loess (L0) 80–40 Dull orange(7.5YR7/4)

Silt Massive-blocky structure, some bio-pores, friable, few earthworm burrows and excrement,some well-rounded spherical pellets, 30–50 cm in thickness.

Palaeosol (S0-upper) 120–80 Bright reddishbrown (5YR5/6)

Silt Granular-blocky structure, porous, relatively firm, medium abundant earthworm burrows andexcrement. Abundant well-rounded spherical pellets, some secondary calcite crystallite(pseudomycelia) in the pores and crevices, 30–80 cm in thickness. Well developed UsticIsohumisol (Chernozem).

Red clayc (RC) 250–120 Bright reddishbrown (2.5YR5/8)

Clay With rolling, wavy and conglomerated structure, very firm, with some stones, earth clods andhuman remains including pottery shards, burnt earth, ash and charcoal are enwrapped, 100–300 cm in thickness. Deposited by mudflows coming along the gullies from the hillsidesconsisting of the unconsolidated Tertiary red clay.

Palaeosol (S0-lower) 330–250 Dull reddishbrown (5YR5/3)

Silt Blocky structure, porous, firmly, medium abundant earthworm burrows and excrement,abundant secondary calcite crystallite (pseudomycelia) in the pores and crevices looking likefrosted, 70–90 cm in thickness. Well developed Ustic Isohumisol (Chernozem), and the surfacerepresenting the ground occupied by the people of the Qijia Culture (4.20–3.95 ka BP), on whichhuman skeletons, pottery vessels, charcoal, burnt earth and house floors were retrieved.

Transitional loess (Lt) 420–330 Dull orange(7.5YR7/3)

Silt Massive-blocky structure, some bio-pores, friable, few vertical earthworm burrows, 100–130 cm in thickness, accumulated eolian dust with weak weathering.

Malan loess (L1-1) 1000–420 Yellow orange(10YR7/4)

Silt Massive structure, some bio-pores, very friable, calcareous rich, 600–1000 cm in thickness, withinsertion of lenticular form of gully deposits at different levels.

Fluvial deposits (T2-al) 1500–1000 Bright yelloworange (10YR7/6)

Coarsesand

Coarse sand, loose, with lenticular beddings, raised flood plain deposit overlying on the well-rounded gravels of the raised river bed deposit, forming the second terrace of the Yellow River.

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measured by SAR to build an SGC growth curve, and then the other10 natural aliquots were measured and projected on the SGCgrowth curve to obtain De values. The final De for a sample is theaverage of all the De measured (Table 3).

To reach the appropriate preheat conditions for De determina-tion, a preheat temperature plateau test was conducted for sampleXLJ-1. We tested preheat temperatures from 180 �C to 300 �C atintervals of 20 �C for 10 s and a cut-heat of 220 �C for 10 s, usinga heating rate of 5 �C s�1 and three aliquots for every temperaturepoint. A plateau was observed from 200 �C to 260 �C (Fig. 3A). Therecuperation effect of XLJ-1 varied only from 0.2% to 4.7% withtemperature.

Frequent stimulation and preheating can transform the shallowbut difficult-to-bleach traps into OSL traps, and strengthen theintensity of the luminescence signal, leading to an overestimationof De values (Aitken, 1998; Murray and Olley, 2002). Therefore, athermal transfer test was performed on XLJ-1. First, two room tem-perature optical stimulations using the blue diodes for 100 s wereused to bleach the aliquots, with a 10,000 s room temperature stor-age between the two stimulations so that any charge transferredinto the 110 �C TL trap has time to thermally decay. Next, we testedpreheat temperatures from 180 �C to 300 �C at intervals of 20 �C for10 s and a cut-heat of 220 �C for 10 s, using a heating rate of5 �C s�1 and three aliquots for every temperature point. The resultsindicate that the thermal transfer effect is very small from 200 �Cto 260 �C and only varies in the range of (0.10 ± 0.03)–(0.65 ± 0.06) Gy (Fig. 3B). Relative to the OSL age of (3.83 ± 0.12)ka, the resulting error only varies in the range of 0.7%–5.0%. The

Table 2Summary of OSL dating results, including De and dosimetry, parameters.

Sample ID Stratigraphy Depth (cm) U (ppm) Th (ppm) K (%

XLJ-B-1 Topsoil, TS 35 2.08 ± 0.09 10.00 ± 0.28 1.90XLJ-1 Palaeosol, S0 105 2.43 ± 0.09 11.30 ± 0.32 2.07XLJ-2 Palaeosol, S0 315 3.80 ± 0.12 12.40 ± 0.33 2.05XLJ-3 Transitional loess, Lt 375 3.16 ± 0.11 11.10 ± 0.31 2.00XLJ-B-2 Malan Loess, L1-1 470 2.68 ± 0.10 9.35 ± 0.28 1.74XLJ-4 Malan Loess, L1-1 495 3.03 ± 0.11 10.50 ± 0.30 2.04XLJ-B-3 Malan Loess, L1-1 770 3.06 ± 0.11 10.80 ± 0.30 1.84XLJ-5 Malan Loess, L1-1 945 2.89 ± 0.11 11.10 ± 0.31 1.94

thermal transfer effect can therefore be ignored because of aninsignificant De value variant.

A dose recovery test (Murray and Wintle, 2003) was conductedfor XLJ-1. First, two room temperature optical stimulations usingblue diodes for 100 s were used to bleach the aliquots, with a10,000 s room temperature storage between the two stimulationsso that any charge transferred into the 110 �C TL trap had timeto thermally decay. Next, a laboratory dose of 16.03 Gy was per-formed. Finally, we tested preheat temperatures from 180 �C to300 �C at intervals of 20 �C for 10 s and a cut-heat of 220 �C for10 s, using a heating rate of 5 �C s�1 and three aliquots for everytemperature point. From 200 �C to 260 �C, the recovered dose var-ied between (14.61 ± 0.78) Gy and (15.91 ± 1.18) Gy. The ratio ofgiven to measured dose was 1.01–1.10 (Fig. 3C).

The ‘‘recycling ratio’’ was used to check for sensitivity changecorrection (Murray and Wintle, 2000). In the preheat temperatureplateau test and the thermal transfer test, the recycling ratio of allaliquots falls into the range of 0.93–1.05 between 200 �C and260 �C (Fig. 3D), indicating that the sensitivity change had beenadequately corrected. Therefore, a preheat temperature of 260 �Cand a cut-heat of 220 �C were selected for the regeneration and testdoses, respectively, in routine De determination.

The typical OSL decay curves of the natural dose, the regenera-tion dose and the following test dose for the samples XLJ-1 andXLJ-3 are shown in Fig. 4A and C, respectively. Their OSL signals de-cayed significantly during the first 0.3 s stimulation, suggesting thedominance of the fast OSL component. The regeneration dose of0 Gy was used to measure recuperation, which was calculated by

) Water content (%) Dose rate (Gy/ka) De (Gy) OSL age (ka)

± 0.06 13.8 2.82 ± 0.06 2.14 ± 0.07 0.76 ± 0.02± 0.06 10.5 3.46 ± 0.07 13.24 ± 0.29 3.83 ± 0.12± 0.06 9.3 3.87 ± 0.08 32.94 ± 0.69 8.52 ± 0.26± 0.07 8.2 3.33 ± 0.06 37.11 ± 1.25 11.15 ± 0.44± 0.06 9.0 2.94 ± 0.06 43.25 ± 0.69 14.70 ± 0.39± 0.06 8.2 3.28 ± 0.06 58.01 ± 0.19 17.69 ± 0.34± 0.06 12.2 2.94 ± 0.06 70.43 ± 3.57 24.00 ± 1.31± 0.06 14.0 2.97 ± 0.06 94.84 ± 5.60 31.94 ± 1.99

Fig. 3. (A) Preheat temperature plateau test using the sample XLJ-1. (B) Thermal transfer test using the sample XLJ-1. (C) The average G/M ratio obtained at each preheattemperature. (D) The recycling ratio obtained at each preheat temperature.

Y. Zhang et al. / Journal of Asian Earth Sciences 87 (2014) 157–164 161

dividing the corrected OSL intensity of the zero dose by that of thenatural cycle. The recuperation effect was less than 2% for all ali-quots. Two typical growth curves of two aliquots for XLJ-1 andXLJ-3 are shown in Fig. 4B and D, respectively.

Fig. 4. (A) Decay curves and (B) growth curve for a relatively young sample XLJ-

In the case of wind-borne sediments, resetting of the latentluminescence signal to a sufficient near-zero residual value almostalways occurs (Hilgers et al., 2001), especially in Chinese loess. Weapplied the equivalent dose frequency distribution to assess the

1. (C) Decay curves and (D) growth curve for a relatively old sample XLJ-3.

Fig. 5. (A) Equivalent dose frequency distribution for a relatively young sample XLJ-1. (B) Equivalent dose frequency distribution for a relatively old sample XLJ-3.

Table 3Equivalent doses for the 8 samples for the Xialajia section.

Sample ID Stratigraphy Aliquot number (test) Aliquot number (calculated) De-SAR (Gy) De-SGC (Gy) De-SAR/De-SGC De (Gy)

XLJ-B-1 Topsoil, TS 12a + 10b 9a + 8b 2.14 ± 0.05 2.13 ± 0.14 1.00 2.14 ± 0.07XLJ-1 Palaeosol, S0-upper 12a + 10b 12a + 8b 13.19 ± 0.33 13.33 ± 0.55 0.99 13.24 ± 0.29XLJ-2 Palaeosol, S0-lower 12a + 10b 12a + 9b 32.58 ± 0.86 33.43 ± 1.16 0.94 32.94 ± 0.69XLJ-3 Transitional loess, Lt 12a + 10b 10a + 10b 37.84 ± 2.05 36.38 ± 1.53 1.04 37.11 ± 1.25XLJ-B-2 Malan Loess, L1-1 12a + 10b 12a + 8b 43.18 ± 0.93 43.33 ± 1.08 0.99 43.25 ± 0.69XLJ-4 Malan Loess, L1-1 12a + 10b 12a + 8b 58.98 ± 2.75 56.56 ± 4.84 1.04 58.01 ± 0.19XLJ-B-3 Malan Loess, L1-1 6a + 10b 5a + 8b 71.66 ± 0.80 69.20 ± 5.45 1.04 70.43 ± 3.57XLJ-5 Malan Loess, L1-1 6a + 10b 3a + 6b 95.16 ± 4.88 94.63 ± 8.39 1.01 94.84 ± 5.60

a Aliquot numbers using SAR method.b Aliquot numbers using SGC method.

Fig. 6. The relationship between OSL ages and the depth in the Xialajia section in the Guanting Basin along the upper Yellow River valley.

162 Y. Zhang et al. / Journal of Asian Earth Sciences 87 (2014) 157–164

Fig. 7. Stratigraphic correlations among the Shiliucun section in the Weihe River valley, the Ertangcun section on top of the loess tableland in Changwu County (Huang et al.,2003, 2009), and the Xialajia section in the Guanting Basin along the upper Yellow River valley.

Y. Zhang et al. / Journal of Asian Earth Sciences 87 (2014) 157–164 163

bleaching history of samples (Olley et al., 1998). The equivalentdose values of the samples (XLJ-1, XLJ-3) fitted a normal Gaussiandistribution (Fig. 5A and B). This indicates that they were wellbleached before deposition. Thus, the average De value of all thewell-bleached aliquots was used for the De determination of eachsample.

3.4. Dose rate determination

The U, Th and K content of the samples was determined by neu-tron activation analysis in the China Institute of Atomic Energy,Beijing (Table 2). Water content (mass of moisture/dry mass;Aitken, 1985) was estimated by weighing the samples before andafter drying (the samples were dried at 105 �C for 24 h), and theestimates were revised based on previous loess-soil water contentdata from the Qinghai province (Xu et al., 2010). An alpha effi-ciency (a-value) of 0.035 ± 0.003 was adopted for the 40–63 lmgrains (Lai et al., 2008) and radioactive equilibrium was assumed.The calculation was performed in Age.exe (Grün, 2003).

4. Results and discussion

The equivalent dose values, dose rates and OSL ages are pre-sented in Tables 2 and 3. The OSL ages fall within the range of(31.94 ± 1.99) ka to (0.76 ± 0.02) ka, and the errors associated withindividual ages range from 2.63% to 6.23%. At each sampling site,ages increase with depth (Fig. 5).

Four OSL samples were collected from the L1-1 (Fig. 6) in the XLJsection, providing OSL ages from (31.94 ± 1.99) ka to(14.70 ± 0.39) ka, which indicates that most of the loess was depos-ited during the late last glacial period (35.00–11.50 ka, MIS-2). Thiscorrelates well with the Malan Loess (L1L1) that is distributedwidely over the Longxi Loess Plateau (Chen et al., 1996).

Combining our results with previous research (Li et al., 1996; Panet al., 2007), the second terrace in the Guanting Basin along theupper Yellow River formed 35.00 ka ago.

The sample collected from the bottom of the transitional loess(Lt) yielded an OSL age of (11.15 ± 0.44) ka, corresponding to theend of the last glacial and the start of the Holocene at 11.50 ka(Alley et al., 1993; Huang et al., 2003, 2006, 2009). Ages obtainedfrom the bottom and the top of the palaeosol (S0) were(8.52 ± 0.26) ka and (3.83 ± 0.12) ka, respectively, showing thatthe Holocene Climatic Optimum had started by 8.50 ka. Based onprevious studies (Huang et al., 2003, 2006, 2009), the Lt

accumulated during 11.50–8.50 ka and the S0 developed during8.50–3.10 ka (Fig. 7). The age calculated from the bottom of thetopsoil (TS) was (0.76 ± 0.02) ka. Thus, we can conclude that duringthe late Holocene, from 3.10 ka to the present, the S0 has been bur-ied by the accumulation of the recent loess (L0) and the TS (Fig. 7).This indicates that pedogenesis of the S0 ended by 3.10 ka, and theL0 and the TS have accumulated over it thereafter.

Therefore, based on the pedostratigraphy of the investigatedsection (Chen et al., 1996; Huang et al., 2003, 2006, 2009) andthe 14C ages (Zhang et al., 2003, 2005, 2009), the XLJ section is com-posed of Malan Loess (L1-1) of the late last glacial period (MIS-2)and the Holocene loess-soil sequences.

5. Conclusions

We have established an OSL geochronology for the stratigraphyof the Lajia Ruins in the Guanting Basin along the upper YellowRiver valley. Tests of the luminescence characteristics (preheattemperature, laboratory dose recovery, thermal transfer, OSL de-cay, and the growth curve) confirm that the resultant OSL age isreliable. The OSL age ranges from (31.94 ± 1.99) ka to(0.76 ± 0.02) ka. Combined with the pedostratigraphy of the

164 Y. Zhang et al. / Journal of Asian Earth Sciences 87 (2014) 157–164

investigated sections (Chen et al., 1996; Huang et al., 2003, 2006,2009), the XLJ section is composed of the Malan Loess (L1-1) ofthe late last glacial (MIS-2) and the Holocene loess-soil sequences.

Acknowledgments

We thank the Editors and anonymous reviewers for theirvaluable comments and constructive suggestions. This work wassupported by the grants from the National Science Foundationof China (41030637, 41271108, 41371029), the Ph.D. ProgramsFoundation from Ministry of Education of China (20110202130002) and the Excellent Doctoral Dissertation Foundation fromShaanxi Normal University of China (X2012YB04).

Appendix A. Supplementary material

Supplementary data associated with this article can be found, inthe online version, at http://dx.doi.org/10.1016/j.jseaes.2014.02.002. These data include Google maps of the most important areasdescribed in this article.

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