Investigating soil magnetic properties with pedogenic variation along a precipitation gradient in loess-derived soils of the Golestan province, northern Iran

Journal Pre-proof Investigating soil magnetic properties with pedogenic variation along a precipitation gradient in loess-derived soils of the Golestan province, northern Iran J. Sharifigarmdareh, F. Khormali, S. Scheidt, C. Rolf, M. Kehl, M. Frechen PII:

S1040-6182(19)30859-6

DOI:

https://doi.org/10.1016/j.quaint.2019.11.022

Reference:

JQI 8055

To appear in:

Quaternary International

Received Date: 14 May 2018 Revised Date:

5 October 2019

Accepted Date: 7 November 2019

Please cite this article as: Sharifigarmdareh, J., Khormali, F., Scheidt, S., Rolf, C., Kehl, M., Frechen, M., Investigating soil magnetic properties with pedogenic variation along a precipitation gradient in loessderived soils of the Golestan province, northern Iran, Quaternary International, https://doi.org/10.1016/ j.quaint.2019.11.022. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.

1

Investigating soil magnetic properties with pedogenic variation along a precipitation

2

gradient in loess-derived soils of the Golestan province, northern Iran

3 4

J. Sharifigarmdareha, F. Khormalia,* S. Scheidtb,c, C. Rolf c, M. Kehld, M. Frechenc

5 6

a

7

Resources, Iran.

8

b

Institute of Geology and Mineralogy, University of Cologne, Germany

9

c

Leibniz Institute for Applied Geophysics (LIAG), Germany.

10

d

Institute of Geography, University of Cologne, Germany.

Department of Soil Sciences, Faculty of Agriculture, Gorgan University of Agricultural Sciences and Natural

11 12 13 14

* Corresponding author: [email protected]

15

Abstract

16

In the Golestan province in northern Iran extensive loess deposits, and widespread loess-derived soils crop out.

17

While a strong precipitation gradient (200 to 700 mm per year) from North to South is characteristic, temperature

18

differences are negligible (17 - 18 °C per year). Recently, many studies on loess-derived palaeosols and modern

19

soils from this region were published; However, in these publications only limited information on the magnetic

20

properties of loess and loess-derived soils is given, nor the potential of these properties to be applied as proxies for

21

palaeoclimate reconstruction. In order to study soil magnetic properties along the precipitation gradient in the

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Golestan province, six pedons of modern soils were selected. The physicochemical properties, the clay mineralogy

23

and magnetic parameters of soil samples were analysed. Susceptibility measurements (20.2 to 130.77×10-8 m3kg-1),

24

ARM susceptibility values (0.00489 to 0.068 m3kg-1), IRM values (0.0027 to 0.0105 Am2kg-1), and hysteresis

25

measurements provide significant evidences for an increase of the content of fine grained ferromagnetic minerals

26

with increasing mean annual precipitation (MAP). Simultaneously, the amount of SP sized particles increase.

27

Magnetite, maghemite, and hematite are the major magnetic minerals in the studied samples, whereby magnetite

28

seems to be dominant in the soils of the loess plateau of northern Iran. By presenting data from this region of the

29

northern Iran for the first time, another example is provided for the application of magnetic properties as proxies for

30

the reconstruction of the paleoclimate. The results are compared to data of the Chinese loess plateau, the Russian

31

steppe and loessic soils from the midwestern United State with similar relations of pedogenic susceptibility and

32

MAP.

33 34 35

Keywords: Pedogenesis, Loess, Magnetic Properties, Northern Iran

36

1. Introduction

37

Soil magnetic properties in sedimentary environments are very sensitive to physicochemical conditions (Evans and

38

Heller, 2003). Therefore, the composition, concentration and granulometry of magnetic minerals in soils provide

39

essential information for climate interpretations (Maher et al., 2003). In unpolluted and well-drained soils, a strong

40

positive correlation of pedogenic magnetic properties with precipitation is well known (Maher et al., 1994; Maher et

41

al., 2003; Geiss and Zanner, 2007, Li et al., 2015). Hereby, the contribution of ferromagnetic minerals is usually

42

higher in the soil horizon than in their parent material (Maher et al., 2002, Geiss and Zanner, 2007). The distribution

43

of the minerals can be monitored by the magnetic susceptibility which is especially sensitive to the quantity of fine-

44

grained pseudo-single-domain (SP) and stable-single-domain (SSD) magnetite and maghemite grains (e.g., Heller

45

and Evans, 1995; Song et al., 2010; Balsam et al., 2011; Marković et al., 2012, Maxbauer et al., 2016). Magnetite

46

usually originates from parent material (Schwertmann and Taylor, 1989) while maghemite particles have a

47

pedogenic origin and form during pedogenic processes (Liu et al., 2007; Yang et al., 2013). Besides ferrimagnetic

48

minerals (magnetite, maghemite) antiferromagnetic (hematite or goethite) minerals may also be enhanced by soil

49

forming processes (Geiss et al., 2004).

50

This study focus on modern soils from the Golestan province in northern Iran. A number of studies on loess-derived

51

palaeosols and modern soils from the region got available over the last decade. A preliminary study of Frechen et al.

52

(2009) demonstrated magnetic enhancement within a palaeosol in a loess sequence located in an area of northern

53

Iran with sub-humid conditions at present times. Khormali and Kehl, (2011), Khormali et al. (2012) and Shahriari et

54

al. (2017) studied the effects of the precipitation gradient to the physicochemical and micromorphological properties

55

of northern Iranian loess-derived soils, and report on an increase of the degree of soil development with increasing

56

precipitation. Ghafarpour et al. (2016), Lauer et al. (2017b) and Vlaminck et al. (2018) presented detailed

57

susceptibility records over several cycles of dust accumulation and soil formation in the loess areas of Northern Iran,

58

which are today under semiarid and sub-humid climatic conditions. However, there is no comprehensive study on

59

magnetic properties of loess and soils along the climate gradient in northern Iran; the composition and granulometry

60

of magnetic minerals and also the change of magnetic properties with different precipitation is still under debate.

61

Therefore, the main objectives of the presented study are 1- to study composition and grain size of magnetic

62

minerals and variation of magnetic properties along the precipitation gradient; 2- to investigate soil

63

magnetism/climate (χ/precipitation) relationship for reconstruction of paleoclimate and 3- to compare the results

64

with pedogenic susceptibility (χmax- χChorizon ) data of similar deposits from the Chinese loess plateau (Maher and

65

Thompson, 1991; 1995; Porter et al., 2001), and the Russian steppe (Maher et al., 2002).

66 67

2. Materials and methods

68

2.1. Study area

69

In the Golestan province extensive loess deposits exist in the so called Iranian loess plateau in the north-eastern parts

70

and on the northern foot slopes of the Alborz Mountains. Currently, there is a precipitation gradient within < 100 km

71

from 200 mm to 700 mm per year in a north-south direction (SWRI, 2000). The mean annual temperature in this

72

region is between 17 and 18 ⁰C (Table 1). Luminescence data showed that the age of parent material in surface soils

73

goes back to the late Pleistocene (16.7 ± 1.1 ka to 20.5 ± 1.8 ka) with dry and cold conditions during this period

74

(Kehl et al., 2005; Frechen et al., 2009; Lauer et al., 2017a; Lauer et al., 2017b). The vegetation density varies from

75

scattered grassland in the north to dense grassland in the typical steppe and finally forest in the south (Table 1).

76 77 78 79 80 81 82 83 84 85 86 87 88 89 90

Figure 1: Location map of the study area and the sites of the modern soils

91

2.2. Sampling and analyses

92

Six well-drained loess derived pedons were selected on stable landforms along the climatic gradient (Fig. 1, Tab. 1).

93

Pedons were dug down to a maximum of 1.6 m below surface and one profile was carefully cleaned for sampling.

94

Soil horizons were identified in the field (Tab. 2) and sampled (Soil Survey Staff, 2014) for physicochemical and

95

mineralogical analyses. Eighty one samples for the rock magnetic analyses were collected in 10 cm intervals using a

96

scraper. The samples were stored in plastic bags. In the rock magnetic laboratory of Leibniz Institute for Applied

97

Geophysics, Hannover (LIAG; branch Grubenhagen), the samples were initially dried. In order to prevent

98

movements of the dry sediment particles the sediment material was pressed into plastic boxes which were closed

99

with plastic caps. The weight of each sample was noted. The remaining material was used for special rock magnetic

100 101 102

analyses and for physicochemical and mineralogical investigations.

103

Table 1: Climate data of the studied regions Region

Vegetation cover

SMR

MAAT (C)

MAP

Altitude

(mm)

(m a.s.l)

Dashli Borun (D-B)

Grassland

Aridic

18

200

54

Khaled Nabi (K-N)

Grassland

Dry Xeric

17.5

330

380

Yelli Badraq (Y-B)

Grassland

Dry Xeric

17

405

385

Kalaleh (K)

Grassland

Dry Xeric

17

480

205

Aq Emam (A-E)

Shrubland

Typic Xeric

17

600

320

Seyyed Miran (S-M)

Forest

Typic Xeric

17

670

218

MAP: Mean annual precipitation; MAAT: Mean annual air temperature: SMR: Soil moisture regime; SWRI - Soil and Water Research Institute Iran (2000). The climatic data are the means of the period 1987-2015. 104 105

2.2.1 Physicochemical and mineralogical characterisation

106

Particle size distribution was determined by hydrometer method (Gee and Bauder, 1986). The soil pH was measured

107

in saturated paste using pH electrode (Salinity Laboratory Staff, 1954) and soil EC was measured in the extract

108

using conductivity meter (Rhoades, 1982). Organic carbon (OC) was determined using a wet combustion method

109

(Nelson and Sommers, 1982). The calcium carbonate equivalent (CCE) was determined by acid neutralization

110

(Salinity Laboratory Staff, 1954). Clay mineralogy was carried out with methodology of Kittrick and Hope, (1963)

111

and Jackson, (1975) and was calculated semi-quantitatively from the relative x-ray peak areas of glycol-treated

112

samples (Johns et al., 1954).

113 114

2.2.2 Magnetic measurements and analyses

115

The plastic boxes filled with the sample material were successively subjected to different measurement procedures

116

to gain information on the concentration, composition and granulometry of ferromagnetic minerals.

117

First, the mass specific magnetic susceptibility χlf (lf stands for low magnetic field) of all samples was measured

118

with the MINIKAPPA (KLF-3) from AGICO (Brno Czech Republic). Then, frequency dependent susceptibility (χfd)

119

was determined from measurements at frequencies of 505 and 5050 Hz and at a field of 400 A/m using a Magnon

120

VFSM susceptibility bridge. The frequency dependence is expressed as χlf (%) = [(χlf- χhf)/ χlf] ×100. Pedogenic

121

susceptibility (χped) was calculated after Maher et al. (1994, 2002), by subtracting the susceptibility of the parent

122

loess (χC-horizon) from the maximum mass specific susceptibility (χmax) values of the A or B horizon (χped = χmax- χC-

123

horizon ).

124

For a selection of 21 samples, which comprised pedogenetically altered and also parent material of each profile, the

125

anhysteretic remanent magnetisation ARM, and the isothermal remanent magnetisation (IRM) was measured. ARM

126

was imparted in an alternating field (AF) of 100 mT with a superimposed 100 µT bias field and is expressed as

127

ARM susceptibility (χARM=ARM/100µT). IRM was created stepwise from 0 to 2.75 T and backfield IRM stepwise

128

from 0 to 300 mT. Both types of remanence were acquired using Magnon PM II pulse magnetiser and measured

129

using 2-G Enterprises Model 760 cryogenic magnetometer. The saturation IRM (SIRM) value is defined as the IRM

130

value measured after the 2.75 mT step, even though samples were not completely saturated. The S-ratio was

131

calculated for these 21 samples after Bloemendal et al. (1992) by the formula (1 + (BF_IRM-0.3T/IRM2.75T))/2.

132

Here, IRM-0.3T represents the remanent magnetisation of the 300 mT backfield step and BF_IRM 2.75T represents

133

the remanent magnetisation obtained after the backfield step. By the use of this definition of the S-ratio, minerals

134

that are saturated in a field of 300 mT are indicated by values close to 1, whereas smaller values show the presence

135

of high coercive minerals.

136

Magnetic hysteresis parameters (saturation magnetisation Ms; saturation remanence Mrs; coercive force Bc and

137

coercivity of remanence Bcr) were determined for 14 selected samples using a EV9 vibration sample magnetometer

138

(VSM) from MicroSense. From each profile those samples were chosen that show the highest mass specific

139

magnetic susceptibility χlf values. Material from the same samples as well as their parent materials were subjected to

140

measurements of the thermal dependence of magnetic susceptibility (χ(T)). χ(T) measurements have been performed

141

using AGICO CS3 furnace apparatus in the temperature range of 20–700 °C. The CS3 furnace works in combination

142

with the MFK1-FA kappa bridge of AGICO. The results of the temperature experiments were interpreted and

143

evaluated by the special software CUREVAL (Hrouda, 1994). All measurements were carried out at the rock

144

magnetic laboratory Grubenhagen of the Leibniz Institute for Applied Geophysics (LIAG) in Germany.

145 146

3. Results and discussion

147

3.1. Morphological, physicochemical and mineralogical properties

148

Table 2 presents the physicochemical properties and classifications of the soils. Soils of the Dashli Borun region

149

with arid soil moisture regime are mainly classified as weakly developed Entisols. With increasing precipitation in

150

the dry xeric regions, Haploxerepts with weakly developed cambic horizons (K-N), Calcixerepts with calcic

151

horizons (Y-B), and Calcixerolls with mollic horizons (K) were observed. With further increased precipitation,

152

available soil moisture and conditions favourable for soil formation increase. Bt horizons were seen in A-E and S-M

153

pedons with 600 mm/yr and 670 mm/yr pointing to sufficient water for leaching, dense vegetation and favourable

154

drainage have provided appropriate condition for translocation of clay and formation of Bt horizon. These horizons

155

show angular to subangular blocky structure and did not effervesce with 10% HCl. As discussed by Khormali et al.

156

(2012), the limited expanding nature of the vermiculitic type of clay minerals and the stable landscape on which they

157

have formed have provided a suitable environment (lower pH and decalcified upper horizons) for the downward

158

translocation of clay and thus formation of thick and more pronounced clay coatings in humid regions and

159

contributed to their preservation.

160

Soil pH also shows a decreasing trend with precipitation ranging from a maximum of 8.3 in the whole depth of D-B

161

in the arid region down to the minimum of 6 in the Bw horizon of S-M in the more humid region. Soil organic

162

carbon ranges from 0.5 % to 5.7 % in the surface soils of D-B and S-M, respectively, shows an increasing trend with

163

precipitation. Leaching of carbonate from upper horizons is observed in most of the studied pedons and is highly

164

intensive in more humid regions. Gypsum is observed in the soils of more arid regions and disappeared in the more

165

humid regions.

166

Clay mineralogical study of soil parent material showed that mica, chlorite, kaolinite and smectite are dominant

167

minerals in the soils. As the amount of precipitation increases along the climate gradient, the amounts of pedogenic

168

vermiculite and smectite increase (Table 3). The soil morphological, physicochemical and mineralogical properties

169

and their variations are in line with previous findings in the same region (Khormali and Kehl, 2011, Khormali et al.,

170

2012).

171 172

Table 2: Physicochemical properties of pedons listed in order of increasing precipitation

173 Region

Horizon

Depth

Colour

(cm)

(moist

pH

EC

CCE

OC

Clay

(dS/m)

Silt

Sand

Gypsum

%

condition) Typic Torriorthents A 0-10 D-B

C Cy

10-50 50-

10YR 6/3

8.3

0.8

20

0.5

21.9

59.1

19.0

3.2

10YR 6/4 10YR 6/4

8.3 8.3

4.7 12.7

20 21

0.3 0.3

19.3 14.1

59.3 62.8

21.4 23.1

3.1 3.9

10YR5/4

7.4

1.8

15

0.7

15.0

73.8

11.2

2.9

10YR6/4 10YR6/3 10YR6/3

7.7 7.6 7.8

0.8 3.6 9.6

16 25 21

0.4 0.2 0.1

15.0 15.0 12.5

68.8 68.8 71.3

16.2 16.2 16.2

2.8 2.8 5.1

10YR 4/3 10YR5/3

8.1 8.3

1.0 0.8

20 24

2.6 1.4

27.3 22.0

65.2 64.5

7.5 13.5

3.1 4.3

100 Typic Haploxerepts A 0-10 K-N

Bw C Cy

10-40 40-90 90110

Typic Calcixerepts A 0-28 Bky1 28-54 Y-B

Bky2 Bky3

54-68 68112

10YR 6/4 10YR 6/4

8.2 7.9

1.1 3.7

27 29

1.0 0.7

21.9 27.1

66.9 65.7

11.2 7.2

3.1 3.1

Bky4

112130

10YR 6/4

7.9

6.7

27

0.6

29.7

62.2

8.1

3.1

C

130150

10YR 6/3

8.6

2.5

25

0.4

29.6

59.3

11.1

3.0

A AB

0-27 27-37

8.1 8.3

0.9 0.5

8 14

3.9 3.3

31.8 29.8

59.4 62.6

8.8 7.6

-

Bk1

37-52

10YR 2/2 10YR 2/23/2 10YR5/3

8.1

0.5

22

2.2

29.7

64.7

5.6

-

Bk2 Bk3

52-89 89-

10YR 6/4 10YR 6/4

8.2 8.1

0.4 0.8

29 29

1.2 0.9

19.4 23.3

71.9 60.9

8.7 15.8

-

Typic Calcixerolls

K

104 Ck

104130

Calcic PachicArgixerolls A 0-30 A-E AB 30-80 Bt

80110 110150

Bk

Calcic Haploxeralfs A 0-10 Bw 10-28 S-M

10YR 6/4

8.2

0.9

24

0.6

22.3

65.4

12.3

-

10YR3/3 10YR2/2

6.8 6.3

1.4 1.3

7

1.9 1.7

40.0 42.5

43.1 46.3

16.9 11.2

-

10YR3/4

6.7

0.8

4

1.0

42.5

48.8

8.7

-

10YR6/4

7.5

0.5

30

0.4

25.0

56.3

18.7

-

10YR3/2 10YR4/4

6.6 6.0

1.1 0.6

7 8

5.7 1.6

40.0 40.0

40.7 46.3

19.3 13.7

-

Bt Btk

28-65 65-90

10YR4/5 10YR5/3

6.5 7.5

1.0 0.6

7 19

0.6 0.7

40.0 30.0

43.1 53.8

16.9 16.2

-

Bk

90120 120-

10YR5/4

7.6

0.3

19

0.5

32.5

53.8

13.7

-

10YR6/4

7.6

0.4

32

0.3

25.0

56.3

18.7

-

Ck

160 D-B: Dashli Borun; K-N: Khaled Nabi; Y-B: Yelli Badraq; K: Kalaleh; A-E: Aq Emam; S-M: Seyyed Miran 174 175

In Dashli Borun the amount of sand is >20 percent. By increasing precipitation, the clay content increases (Table 2)

176

reaching maximum of 40 to 42.5% in pedons S-M and A-E. High clay content indicated intensity of pedogenic

177

processes including weathering of mineral grains, as well as neoformation and illuviation of clay.

178

The effect of climate as the main driving factor in soil formation on loess parent material could be highlighted in the

179

studied soils of the precipitation gradient. As observed, the results show that all the modern soils were developed on

180

the parent loess (C horizons) containing as an average of 62% silt, 21% clay and 17% sand among all the studied

181

pedons. Pedogenic processes driven mainly by climate as the major soil forming factor in the region, have resulted

182

in the formation of different soils and the differentiation of the soil physicochemical, morphological and

183

mineralogical properties.

184 185

Table 3: Semi-quantitative abundances of clay minerals in the studied soils. Hor./Pedon

Illite

Chlorite

Smectite

Kaolinite

Vermiculite

A/D-B

+++

+++

+

+

-

Cy/D-B

+++

+++

+

+

-

A/K-N

+++

+++

-

+

+

Cy/K-N

+++

++

+

+

-

A/Y-B

+++

+++

+

+

-

C/Y-B

+++

+++

+

+

-

A/K

+++

+

+

+

+

C/K

+++

++

-

+

-

Bt/A-E

++

+

+++

+

++

Bk/A-E

+++

++

++

+

-

Bt/S-M

++

+

+++

+

++

Ck/S-M

+++

++

+++

+

-

+++: 30-50%; ++:15-30%; +:<15%; -: not present 186

3.2. Magnetic granularity and composition

187

3.2.1 High temperature susceptibility measurements

188

χ(T) curves were used to identify the kind of magnetic minerals present. As shown in one exemplary illustration of

189

each of the six studied regions in figure 2, all samples regardless of the region of origin and the profile positions

190

show neo-formation of magnetite during heating. This development is proved by the dominant increase of the

191

susceptibility during cooling (dotted lines), and caused by the conversion of Fe-bearing minerals (such as chlorite or

192

oxy-hydroxides). Further, the χ(T) experiments consistently reveal a low rise in susceptibility up to 300 °C followed

193

by a well expressed small maximum kink at 300 °C and a further drop up to 400 °C. This behaviour is only

194

indicated in samples from regions with mean annual precipitation ≤ 330 mm and in samples from lower parts of the

195

pedons. The decreasing susceptibility values above 300 °C are probably caused by the inversion from pedogenic

196

fine-grained maghemite to hematite (e.g., Liu et al., 2005). As can be observed in the χ(T) curves from Dashli Borun

197

(D-B, region with lowest rainfall) to Seyyed Miran (S-M; region with highest rainfall) in figure 2, this behaviour is

198

more pronounced, the greater the annual precipitation is. This points towards the presence of successively increasing

199

amounts of maghemite minerals in regions with higher precipitation, which are simultaneously the regions with the

200

higher mature of soils. Above 420 °C a number of samples show an ascent of the χ(T) curve. Because the increase in

201

values took place over a temperature range of approximately 50°C, it seems to represent the formation of magnetite

202

minerals rather than thermal activation of SP grains (Hopkinson peak). A drop down of all curves at temperatures of

203

580°C indicate the Curie-Temperature of magnetite and specify thereby the presence of this mineral. Finally, the

204

wedge-shaped courses of the χ(T) curves at temperatures over 600°C represent the hematite fraction within the

205

sample material. Depending on the grain size, the chemical composition, the presence of impurities, and possible

206

lattice imperfection the Neel Temperature of hematite range between 630°C and 680°C (De Boer and Dekkers

207

2000). The occurrence of hematite seems not to correlate with the precipitation gradient and may therefore, be a

208

matter of provenance of the parent material of the soils.

209

Following Jordanova (2016) and references therein, such types of thermomagnetic curves are often observed for

210

soils, developed in the temperate continental climate in Europe and in China.

211

212 213

Figure 2: χ(T) experiments on sample material from samples of the individual pedons. List of acronyms for each

214

pedon shown in Figure 2 can be found in Table 1. From each pedon sample material was taken from the uppermost

215

soil below surface (black lines in figure 2) and from lower ones (grey lines in figure 2.). Heating curves marked by

216

solid lines, cooling curves by dotted lines. Susceptibility values are normalized to maximum.

217

218

3.2.2 Bulk susceptibility and frequency dependence of the soil

219

In most of the pedons the surface horizons exhibit a higher mass specific susceptibility χ and frequency dependence

220

of susceptibility χfd than the B and C horizons (Fig. 3a and 3b). Mass specific susceptibility varies between 20.2 ×10-

221

8

222

40 cm below top) of Seyyed Miran (S-M; region with highest rainfall). Thus, χ decreases within the different pedons

223

with depth and increases along the profile in regions with higher rainfall (Fig. 3). Frequency dependence of

224

susceptibility shows a similar trend (Fig. 3). Samples from Dashli Borun and Khaled Nabi (K-N) reveal χfd values

225

below 3 % and weak changes with depth. The deeper parts of Yelli Badraq (Y-B) show only slightly higher χfd

226

values than samples of the former described pedons, while χfd increases two- to threefold towards the top. Samples

227

of the pedons from the regions with higher amount of rainfall (S-M, A-E, K) are characterized by χfd values well

228

above 3% even in the lowest parts of the pedons. Towards the top χfd increases to values around 9 % and 7 % for the

229

pedons of Aq Emam (A-E), Seyyed Miran (S-M), and Kalaleh (K), respectively.

[m3kg-1] in the Cy horizon of Dashli Borun (D-B; lowest rainfall) and 130.77×10-8 [m3kg-1] in the AB horizon (30-

230

231 232 233

Figure 3: (a) Mass specific susceptibility (χlf) and (b) frequency dependence of susceptibility χfd (%) versus depth

234 235

The χ values of the sample materials are predominantly controlled by the content of ferromagnetic minerals, and the

236

grain sizes of these particles. However, the fluctuations of χ are also affected by the presence of organic matter, clay,

237

and calcium carbonate. In the studied region the content of clay minerals (Tab. 3) and organic matter is generally

238

positive correlated with χ (R2= 0.81 and 0.33, respectively; Fig. 4a, b). This positive correlation is probably a

239

secondary relationship, since suitable weathering conditions may cause an increase of the content of clay and

240

magnetic minerals in the sediment. By contrast, the content of the diamagnetic calcium carbonate shows a negative

241

correlation with χ (R2= 0.66; Fig. 4c).

242

243

Figure 4: Figure 4: Variations of average values of clay (a), organic carbon (b) and calcium carbonate (c) versus

244

average of bulk magnetic susceptibility indicating the trend of changes with precipitation. The individual measured

245

values of clay, organic carbon and calcium carbonate are shown in Tab. 2. Please note that no D-B value is available

246

in figure 4b, and D-B and K-N plot almost at the same position in figure 4c.

247 248

For the presence of carbonate, calcium carbonate leaching from the upper strata or from soils (A and B horizons) is a

249

relevant process. Increasing rainfall and biological activity, leads to progressive calcium carbonate dissolution and

250

finally to intense weathering associated with pedogenesis (Zeeden et al., 2017). In the regions of Aq Emam and

251

Seyyed Miran the pH value at the surface and within the Bt horizons is reduced to < 7 (Table 2). This condition

252

promotes weathering of iron bearing silicates and clay minerals, and neoformation of iron oxihydroxides and iron

253

oxides, including magnetite and maghemite and their precursors (Evans and Heller 2003, Balsam et al., 2011). In

254

soil environments these minerals are the stable phases under oxidising conditions, while reduction due to presence of

255

stagnant water or groundwater may cause their destruction (e.g., Maher et al., 2003). The latter effect is unlikely in

256

the studied pedons, because no macroscopic evidence for redoximorphic mottling was found. In summary we

257

conclude that clay, organic matter and calcium carbonate have a secondary relation with magnetic susceptibility.

258

Frequency dependence of susceptibility χfd is sensitive to the presence of very fine superparamagnetic (SP) particles

259

(e.g., Dearing, 1999) formed in soils during the pedogenesis. According to Dearing et al. (1996), the frequency

260

dependence is < 3 % for samples dominated by frequency independent stable single domain (SD) and multi domain

261

(MD) grains. Therefore, values >3 % document fractions of SP grains. Therefore, the uppermost part of Yelli

262

Badraq (Y-B) indicates the presence of SP grains while the particles disappear with depth. This trend is also valid

263

for samples of the pedons from the regions with higher rainfall (S-M, A-E, K). All pedons with mean annual

264

precipitation (MAP) larger than 405 mm reflect soil forming processes with enhanced χ caused by new formed

265

magnetic minerals, detected by frequency dependence clearly greater 3 % (e.g. Dearing et al., 1996; Maher 2011).

266

This result supports the finding in other studies, in which a strong positive correlation (coefficient of determination

267

R2 =+ 0.94) between the logarithm of pedogenic χ and annual rainfall was found (Maher et al., 1994, 2002).

268 269

Figure 5: Frequency depended susceptibility (χfd) versus low field susceptibility χlf

270 271

In order to distinguish soils and highly weathered loess from not weathered loess from the Golestan province a

272

biplot of whole rock χfd vs. χlf is applied (Fig. 5). According to Heller et al. (1991), the simultaneously increasing

273

values in χfd and. χlf reflects increasing pedogenesis (weathering), which induce the enhancement of magnetic

274

susceptibility by neo-formation of magnetic particles in the SP to SD range. The data from the Golestan province is

275

close to that from Xifeng in the Loess Plateau of China (Heller et al., 1991) that is also characterized by χfd values

276

up to 9% and similar data pattern. Pedogenesis effect seems to be comparable to that from Xifeng.

277 278

3.2.3 Isothermal remanent magnetisation (IRM) and anhystertic remanent susceptibility (χARM)

279

The isothermal remanent magnetisation (IRM) acquisition curves of the individual pedons display different

280

behaviours (fig. 6a). The Cy horizon in Dashli Borun pedon has the absolute lowest IRM value whereas the Bt

281

horizon in Seyyed Miran has the highest one. It follows that the lowermost IRM values are recognized for samples

282

from regions with the lowest MAP and vice versa. SIRM intensity variation show the same trend (fig. 6b). Because

283

the IRM and the SIRM are concentration-dependent properties the increase of these values in pedons with more

284

precipitation reflect an increase of the amount of magnetic materials (Evans and Heller, 2003). Hereby, the rapid rise

285

below 300 mT point towards the prominent presence of magnetically soft components, such as magnetite and

286

maghemite. Magnetic enhancement seems to be the deciding factor for the observed increase of soft magnetic

287

minerals with precipitation (Song et al., 2010; Maxbauer et al., 2016). This conclusion is strengthened by correlation

288

of SIRM versus χ shown in figure 6c, which corroborates the close positive relationship of the increase of the

289

concentration of magnetic minerals with precipitation in the Golestan province.

290

However, the IRM is not completely saturated in fields up to 2.75 T (fig. 6a); this reveals the presence of high-

291

coercivity magnetic minerals such as hematite or goethite (Zhang et al., 2016). The relative amounts of high-

292

coercivity (“hard”) remanence to low-coercivity (“soft”) remanence is shown using the S-ratio (fig. 6d). Well-

293

developed soil horizons such as the Bt and Btk soil horizons in Seyyed Miran show the highest S-ratio values (0.87),

294

whereas, less developed ones such as the Cy horizon in Dashli Borun have S-ratios of 0.76. Thereby, a larger portion

295

of high-coercivity minerals were proven in the latter location.

296 297

For the ARM susceptibility (χARM) highest values were found for the pedons of Aq Emam and Seyyed Miran, and

298

lowest values for Dashli Borun (fig. 6f). χARM is preferentially sensitive to the presence of SD particles in sample

299

material (Evans and Heller 2003), and the ratio of χARM and susceptibility is expected to be higher if the average

300

magnetic grain-size is small. Thereby, the dimensionless ratio χARM/ χlf provides information for assessing the

301

magnetic grain sizes distribution, if the dominant magnetic mineral is magnetite. The parameter increases linearly

302

with increasing magnetite concentration, whereby smaller grains are relatively more efficient at acquiring

303

remanence (Evans and Heller 2003). For smaller grains the slope is steeper than for larger ones. The high linearity of

304

the samples from the six pedons forming the clearly defined slope (fig. 6e) is therefore interpreted to indicate sample

305

material owing magnetic grains with similar grain sizes, but in different concentrations. By interpreting the data, we

306

assume particle interaction to be negligible (Yamazaki and Ioka 1997).

307

Taken as a whole, the IRM and χARM values show a positive correlate with the MAP.

308 309

Figure 6: Magnetic parameter and properties of A-horizons of the individual pedons (a) standardised magnetisation

310

versus magnetising field; (b) SIRM versus depth; (c) SIRM versus bulk magnetic susceptibility; (d) S-ratio versus

311

depth (e) χARM versus bulk magnetic susceptibility; (f) χARM versus depth.

312

3.2.4 Hysteresis properties

313

Hysteresis measurements are consulted to gain information on the magnetic grain size and magnetic mineralogy

314

present in the sediment materials. Additional information on the magnetic constituents delivered by the different

315

susceptibility measurements (3.1.2.), as well as by the SIRM and χARM values (3.2.3) are considered for a better

316

interpretation of the hysteresis data.

317 318

In table 4 selected hysteresis parameters are listed for samples from A-horizons of all pedons. All hysteresis loops

319

are only slightly opened with parallel branches. Therefore, only two examples are shown in figure 7.

320 321

Table 4: Hysteresis Parameter as determined from corrected loop hysteresis Sample Site

(Ms) [*10-3 Am2kg-1]

Mrs [*10-3 Am2kg-1]

Bc [mT]

Bcr [mT]

Dashli Borun (D-B)

32.18

3.1

11.6

45.6

Khaled Nabi (K-N)

33.68

3.8

12.0

44.4

Yelli Badraq (Y-B)

35.72

4.2

10.0

34.6

Kalaleh (K)

51.5

7.2

9.2

28.9

Aq Emam (A-E)

60.6

8.6

8.3

25.2

Seyyed Miran (S-

67.4

10.1

8.4

24.3

M) 322

323 324 325

Fig. 7: Examples of hysteresis loops after slope correction and their properties (Ms: Saturation magnetisation, Mrs:

326

Saturation remanence, Bc: Coercive force, Bcr: Coercivity of remanence

327

328

The data show an increase of the magnetisation parameters Ms and Mrs from sample site D-B to sample site S-M,

329

whilst an opposite trend is observed for Bc, and Bcr. The variations in the parameters correspond to the precipitation

330

rates in the sampled regions, with highest values of Ms and Mrs for pedons with highest precipitation and inverse

331

correlation of Bc and Bcr. The magnetisation-intensity parameter Ms shows a similar pattern as the values of the

332

susceptibility, the SIRM, and the χARM. All of these parameters are directly related to the concentration of magnetic

333

minerals. By contrast, the parameter Mrs, Bc and Bcr, are additionally affected by the magnetic grain size and the

334

coercivity of the constituents. The values of the parameters Ms and Mrs are interpreted to reflect the enhancement of

335

SSD magnetite particles during soil formation processes, as frequently described in literature (e.g. Evans and Heller

336

1994; Maher 1998; Hu et al., 2013). Bc is sensitive to the presence of SP particles, which may participate stronger in

337

intermediately developed palaeosols rather than in the highly developed palaeosol units (Deng et al. 2004).

338

However, the variations of the Bc and Bcr values may also be strongly influenced by the amount of magnetically

339

harder minerals in the sediment material. Hysteresis loops of the pedons with low precipitation close at higher

340

magnetic fields than those from samples of the high precipitation areas. Therefore, horizons developed under less

341

precipitation are characterized by significantly higher amounts of antiferromagnetic minerals. Here haematite is

342

most probable. This observation is in accordance with the fluctuations of S-ratios (Fig 6d) and the high temperature

343

susceptibility measurements (Fig. 2). It remains unclear, if the higher portion of high coercive minerals is due to

344

primary accumulated material, or in-situ formation during alteration of the sediment material by soil forming

345

processes.

346 347

Since high coercive minerals are at least partly present, the determination of the magnetic domain state of the

348

magnetic mineral assemblage using Day plots (Day et al., 1977) is complicated (Heslop and Roberts, 2012; Scheidt

349

et al., 2017). The samples with higher coercive fraction are not saturated, whereby Day plot parameters depart from

350

true values. The position of these samples is still depicted in the Day plot for comparison reasons. The ratio of

351

Mrs/Ms is fairly uniform with a mean value of 0.13 ± 0.015 for the 14 samples. Thereby, the day plot indicates an

352

average magnetic domain state of PSD in this study (Fig. 8). This trend is confirmed by the slim shape of the

353

hysteresis loop, that indicate a mixture of SP, SSD, PSD, and possibly MD magnetite particles, without dominance

354

of SSD (Tauxe et al., 1996).

355 356

357 358

Figure. 8: Day plot of variations of 6 soil horizons with low precipitation in Dashli Borun to high precipitation in

359

Seyyed Miran. Please note the change in scale of the Y-axis for enhanced recognisability.

360 361

3.3. Bulk magnetic susceptibility and precipitation

362

Heller and Liu (1982) were the first showing an increase of the amount of magnetic minerals due to pedogenic

363

processes in loess-soil sequences of the Chinese Loess Plateau. Since that study the close relationship between

364

magnetic susceptibility and precipitation, and the application of magnetic properties as paleoclimatic proxy has been

365

shown by a number of studies (e.g. Porter et al., 2001; Maher et al., 2002; 2003; and Geiss and Zanner, 2007). The

366

observed enhancement of the concentration-related magnetic parameters (e.g. χlf; χARM) is shown to be a

367

consequence of pedogenic processes for a huge part of the Eurasian semi-arid loess belt (e.g. Maher, 2016). Highs in

368

palaeosols, and lows in loess, vary by one order of magnitude and indicate, thereby, concentration changes of the

369

ferromagnetic minerals (Evans and Heller, 2003). The repeated change of higher magnetic susceptibility in soils and

370

lower magnetic susceptibility in loess are not only used as indicator for relative temperature and moisture, but

371

provide also a rapid and consistent tool for inter-pedon correlations, even over very long distances across Eurasia

372

(Marković et al., 2012, 2015). However, correlations may be complicated, if contemporary precipitation gradients

373

lead to different alteration of the material.

374

Just as the proxies shown in the former chapters (Fig. 3a, Fig 6), the pedogenic susceptibility (Maher et al., 1994,

375

2002) of the samples from the Golestan province correlate positive with mean average precipitation (Fig. 9). Large

376

differences in magnetic parameters from samples of pedons with precipitation (MAP) of 200 mm to 330 mm do not

377

occur; a low degree of pedogenesis is inferred. In turn, maximum enhancement of magnetic susceptibility in A and

378

B horizons compared to C horizons were found for the pedons with the highest MAP. Overall, the correlation

379

coefficient of pedogenic susceptibility versus precipitation R2 = 0.92 in the region.

380 381

382 383 384

Figure 9: Pedogenic susceptibility (χmax - χC horizon) along the precipitation gradient of studied pedons. Since no C

385

horizon was sampled from Aq Emam, no data is available.

386 387

In a comparison of the pedogenic susceptibility of the northern Iranian modern soils with modern soils form the

388

Chinese loess plateau (Maher et al., 1994; Porter et al., 2001) and the Russian steppe (Maher et al., 2002) the data

389

set of this study shows values in the same range, albeit at the lower end (fig. 10). By contrast, the values of this

390

study are a bit higher than those of loessic soils from the Great Plains in the Midwestern United States. Differences

391

may be due to seasonal variations in precipitation, prevalent mean temperatures or even seasonal temperature

392

changes, as well as further influences, such as differences in microbiological activity. Nonetheless, there is

393

considerable scope for the interpretation. The data set of this study may provide the backbone for future work

394

considering such questions in greater detail.

395 396 397

398 399 400

Figure 10: Variations of pedogenic susceptibility (χmax - χChorizon) material for loessic soils from the Chinese loess

401

plateau (Maher and Thompson, 1995; Porter et al., 2001), the Russian steppe (Maher et al., 2002), modern soils of

402

northern Iran, and loessic soils from the midwestern United State (Geiss and Zanner, 2007).

403

4. Conclusions

404

Investigating the properties of the loess derived modern soils along a precipitation gradient in northern Iran could

405

provide insight to reconstruct past climate conditions and landscape evolution. The present study uses magnetic

406

parameters like χlf, χfd, ARM, IRM and hysteresis parameters to correlate magnetic properties of modern soils with

407

precipitation along a precipitation gradient. It is shown that differences in χlf between the parent material (loess) and

408

the soil horizons are due to enhancement of ferromagnetic minerals. This process is related to the intensity of

409

pedogenesis, which in turn correlates with the mean annual precipitation along the studied precipitation gradient in

410

the Golestan province.

411

Susceptibility measurements (χlf) are shown to be an efficient proxy for identification of soil forming processes.

412

Overall, the values decrease within the different pedons with depth and increase along the pedon in regions with

413

higher rainfall. The calculation of the pedogenic susceptibility reveal an almost linear correlation with the amount of

414

precipitation in the studied region.

415

Ferromagnetic minerals like magnetite and maghemite clearly dominate all magnetic properties. However, high

416

coercive minerals are also present in the studied sites. There might be a more or less negative correlation with MAP

417

but influence of different provenances of the parent material are not taken into account in this study.

418

The ratio between χ and pedogenesis is similar to that of modern soils from the Chinese Loess Plateau and the

419

Russian Steppe.

420 421

References

422

Balsam, W.L., Ellwood, B.B., Ji, J., Williams, R.R., Long, X., Hassani, A.E., 2011. Magnetic susceptibility as a

423

proxy for rainfall: worldwide data from tropical and temperate climate. Quaternary Science Reviews 30, 2732-

424

2744.

425

Bloemendal, J., King, J.Hall, F., Doh, S.J., 1992. Rock magnetism of Late Neogene and Pleistocene deep‐sea

426

sediments: Relationship to sediment source, diagenetic processes, and sediment lithology. Journal of

427

Geophysical Research: Solid Earth (1978–2012), 97, 4361-4375.

428 429 430 431 432 433

Day, R., Fuller, M., Schmidt, V.A., 1977. Hysteresis properties of titanomagnetites: Grain-size and compositional dependence. Physics of the Earth and planetary interiors 13, 260–267. De Boer, C.B., Dekkers, M.J., 2000. Magnetic properties of natural and synthetic hematite. Geologica Carpathica Bratislava June, 51, 185. Dearing, J., 1999. Magnetic susceptibility. In: Walden, J., Oldfield, F., Smith, J. (Eds.), Environmental Magnetism: a Practical Guide. Technical Guide, vol. 6. Quaternary Research Association, London, 35–62.

434

Dearing, J.A., Dann, R.J.L., Hay, K., Lees, J.A., Loveland, P.J., Maher, B.A., O’Grady, K., 1996: Frequency-

435

dependent susceptibility measurements of environmental materials. – Geophysical Journal International 124,

436

228‒240.

437

Deng, C., Zhu, R., Verosub, K. L., Singer, M. J. & Vidic, N. J., 2004. Mineral magnetic properties of loess/paleosol

438

couplets of the central loess plateau of China over the last 1.2 Myr. Journal of Geophysical Research: Solid

439

Earth, 109, (B01103).

440 441 442 443 444 445 446 447

Evans, M. E., Heller, F., 1994. Magnetic enhancement and palaeoclimate: study of a loess/palaeosol couplet across the loess plateau of China. Geophysical Journal International 117, (1): 257–264. Evans, M.E., Heller, F., 2003. Environmental Magnetism-principles and Applications of Environmagnetics. Academic Press, New York, 1-299. Frechen, M., Kehl, M., Rolf, C., Sarvati, R., Skowronek, A., 2009. Loess chronology of the Caspian lowland in northern Iran. Quaternary International 198, 220-233. Gee, G.W., Bauder, J.W., 1986. Particle-size analysis. In: Klute, A. (Eds.), Methods of Soil Analysis. Part I, Physical and Mineralogical Methods, second eds. Agronomy Vol. 9, 383–411.

448 449 450 451 452 453

Geiss, C.E., Zanner, C.W., 2007. Sediment magnetic signature of climate in modern loessic soils from the Great Plains, Quaternary International 162, 97–110. Geiss, C.E., Zanner, C.W., Banerjee, S.K., Minott, J., 2004. Signature of magnetic enhancement in a loessic soil in Nebraska, United States of America. Earth and Planetary Science Letters 228 (3/4), 355-367. Ghafarpour, A., Khormali, F., Balsam, W., Karimi, A., Ayoubi, S., 2016. Climatic interpretation of loess-paleosol sequences at Mobarakabad and Aghband, Northern Iran. Quaternary Research 86(1), 95-109.

454

Heller, F., Evans, M. E., 1995. Loess magnetism. Reviews of Geophysics 33, 211 –240.

455

Heller, F., Liu, T.S., 1982. Magnetostratigraphical dating of loess deposits in China. Nature 300, 431-433.

456

Heller, F., Liu, X., Liu, T., Xu, T., 1991. Magnetic susceptibility of loess in China. Earth and Planetary Science

457 458 459

Letters 103, (1–4): 301-310. Heslop, D., Roberts, A., 2012. Unmixing Magnetic Hysteresis Loops, EGU General Assembly Conference Abstracts, 3758.

460

Hrouda, F., 1994. A technique for the measurement of thermal changes of magnetic susceptibility of weakly

461

magnetic rocks by the CS-2 apparatus and KLY-2 Kappabridge. Geophysical Journal International 118, 604–

462

612.

463 464 465 466 467 468 469 470 471 472 473 474 475 476

Hu, P.X., Liu, Q.S., Torrent, J., Barrón, V., Jin, C., 2013. Characterizing and quantifying iron oxides in Chinese loess/paleosols: implications for pedogenesis. Earth and Planetary Science Letters 369–370, 271–283. Jackson, M.L., 1975. Soil Chemical Analysis, Advanced Course. University of Wisconsin, College of Agriculture, Department of Soil Science, Madison, WI. Johns, W.D., Grim, R.E., Bradley, W.F., 1954. Quantitative estimation of clay minerals by diffraction methods. Journal of Sedimentary Petrology 24, 242-251. Jordanova, N., 2016. Soil Magnetism Applications in Pedology, Environmental Science and Agriculture. Academic Press, pp 445. Kehl, M., Frechen, M., Skowronek, A., 2005. Paleosols derived from loess and loess like sediments in the Basin of Persepolis, Southern Iran. Quaternary International 140, 135-149. Khormali, F., Kehl, M., 2011. Micromorphology and development of loess-derived surface and buried soils along a precipitation gradient in Northern Iran. Quaternary International 234, 109-123. Khormali, F., Ghergherechi, S., Kehl, M., Ayoubi, S., 2012. Soil formation in loess derived soils along a subhumid to humid climate gradient, Northeastern Iran. Geoderma 179-180, 113-122.

477

Kittrick, J. A., Hope, E. W., 1963. A procedure for the particle-size separation of soils for x-ray diffraction analysis.

478

Soil Science 96 (5), 319-325.

479

Lauer, T., Frechen, M., Vlaminck, S., Kehl, M., Lehndorff, E., Shahriari, A., Khormali, F., 2017a. Luminescence-

480

chronology of the loess palaeosol sequence Toshan, Northern Iran-A highly resolved climate archive for the

481

last glacial-interglacial cycle. Quaternary International 429 (Part B), 3-12.

482

Lauer, T., Vlaminck, S., Frechen, M., Rolf, C., Kehl, M., Sharifi, J., Khormali, F., 2017b. The Agh Band loess-

483

palaeosol sequence-a terrestrial archive for climatic shifts during the last and penultimate glacial-interglacial

484

cycles in a semiarid region in Northern Iran. Quaternary International 429 (Part B), 13-30.

485

Li, G., Xia, D., Jin, M., Jia, J., Liu, J., Zhao, S., Wen, Y., 2015. Magnetic characteristics of loess paleosol sequences

486

in Tacheng, northwestern China, and their paleoenvironmental implications. Quaternary International 372, 87-

487

96.

488 489

Liu, Q., Deng, C., Torrent, J., Zhu, R., 2007. Review of recent developments in mineral magnetism of the Chinese loess. Quaternary Science Reviews 26, 368-385.

490

Liu, Q., Deng, C., Yu, Y., Torrent, J., Jackson, M. J., Banerjee, S. K., Zhu, R., 2005. Temperature dependence of

491

magnetic susceptibility in an argon environment: Implications for pedogenesis of Chinese loess/palaeosols.

492

Geophysical Journal International 161, 102-112.

493 494 495 496 497 498

Maher, B. A., 2016. Palaeoclimatic records of the loess/palaeosol sequences of the Chinese Loess Plateau. Quaternary Science Reviews 154: 23-84. Maher, B.A., 2011. The magnetic properties of Quaternary aeolian dusts and sediments and their palaeoclimatic significance. Aeolian Research 3, 87-144. Maher, B. A., 1998. Magnetic properties of modern soils and quaternary loessic paleosols: Paleoclimatic implications. Palaeogeography, Palaeoclimatology, Palaeoecology 137, (1-2): 25-54.

499

Maher, B.A., Alekseev, A., Alekseeva, T., 2003. Magnetic mineralogy of soils across the Russian Steppe: climatic

500

dependence of pedogenic magnetite formation. Palaeogeography, Palaeoclimatology, Palaeoecology 201, 321-

501

341.

502 503 504 505

Maher, B.A., Alekseev, A., Alekseeva, T., 2002. Variations of soil magnetism across the Russian steppe: its significance for use of soil magnetism as a paleorainfall proxy. Quaternary Science Reviews 21, 1571–1576. Maher, B.A., Thompson, R., 1995. Paleorainfall reconstructions from pedogenic magnetic susceptibility variations in the Chinese loess and paleosols. Quaternary Research 44, 383–391.

506

Maher, B.A., Thompson, R., 1991. Mineral magnetic record of the Chinese loess and palaeosols. Geology 19, 3-6.

507

Maher, B.A., Thompson, R., Zhou, L.P., 1994. Spatial and temporal reconstructions of changes in the Asian

508

palaeomonsoon- a new mineral magnetic approach. Earth and Planetary Science Letters 125, 461–471.

509

Marković, S.B., Hambach, U., Stevens, T., Jovanovic, M., O’Hara-Dhand, K., Basarin, B., Lu, H., Smalley, I.,

510

Buggle, B., Zech, M., Svircev, Z., Sümegi, P., Milojkovic, N., Zöller, L., 2012. Loess in the Vojvodina region

511

(Northern Serbia): an essential link between European and Asian Pleistocene environments. Netherlands

512

Journal of Geosciences 91, 173-188.

513

Marković, S.B., Stevens, T., Kukla, G.J., Hambach, U., Fitzsimmons, K.E., Gibbard, P., Buggle, B., Zech, M., Guo,

514

Z., Hao, Q., Wu, H., O'Hara-Dhand, K., Smalley, I.J., Újvári,G., Sumegi, P., Timar-Gabor, A., Veres, D.,

515

Sirocko, F., Vasiljević, D.-A., Jary, Z.,Svensson, A., Jović, V., Lehmkuhl, F., Kovacs, J., Svircev, Z., 2015.

516

Danube loess stratigraphy – towards a pan European loess stratigraphic model. Earth Science Reviews 148,

517

228–258.

518

Maxbauer, D.P., Feinberg, J.M., Fox, D.L., 2016. Magnetic mineral assemblages in soils and paleosols as the basis

519

for paleoprecipitation proxies: A review of magnetic methods and challenges. Earth Science Reviews 155, 28-

520

48.

521 522 523 524 525 526 527 528

Nelson, D.W., Sommers, L.E., 1982. Total carbon, organic carbon, and organic matter. In: Page, A.L. (Ed.), Methods of Soil Analysis, Part II. American Society of Agronomy, Madison. WI. 539–579. Porter, S.C., Hallet, B., Wu, X., An, Z., 2001. Dependence of near-surface magnetic susceptibility on dust accumulation rate and precipitation on the Chinese loess plateau. Quaternary Research 55, 271–283. Rhoades, J.D., 1982. Soluble salts. In: Page, A.L. (Ed.), Methods of Soil Analysis, Part II, second ed., ASA, Monograph, No. 9, Madison, WI, 167-179 Salinity Laboratory Staff, 1954. Diagnosis and Improvement of Saline and Alkali Soils. United States Department of Agriculture Handbook No. 60Washington, DC.

529

Scheidt, S., Egli, R., Frederichs, T., Hambach, U., Rolf, C., 2017. A mineral magnetic characterization of the Plio-

530

Pleistocene fluvial infill of the Heidelberg Basin (Germany). Geophysical Journal International 210, (2): 743-

531

764.

532 533

Schwertmann, U., Taylor, R.M., 1989. Iron oxides, In:Dixon, J.B., Weed, S.B. (Eds.), Minerals in soil environments, 2nd ed. SSSA, Madison, WI, 379–438.

534

Shahriari, A., Khormali, F., Blasing, M., Vlaminck, S., Kehl, M., Frechen, M., Karimi, A.Lehndorff, E. 2017.

535

Biomarkers in modern and buried soils of semi-desert and forest ecosystems of northern Iran. Quaternary

536

International 429: 62-73.

537 538

Soil Survey Staff. 2014. Keys to soil Taxonomy, 12th ed. U.S. department of agriculture, Natural resources conservation service.

539

Song, Y.G., Shi, Z.T., Fang, X.M., Nie, J.S., Naoto, I., Qiang, X.K., Wang, X.L., 2010. Loess magnetic properties in

540

the Ili Basin and their correlation with the Chinese Loess Plateau. Science in China: Earth Sciences 53 (3), 419-

541

431.

542 543 544 545

SWRI - Soil and Water Research Institute Iran, 2000. Soil Resources and Use Potentiality Map of Iran (1:1 000 000), Tehran. Tauxe, L., Mullender, T., Pick, T., 1996. Potbellies, wasp-waists, and superparamagnetism in magnetic hysteresis, J. geophys. Res., 101, 571–583.

546

Vlaminck, S., Kehl, M., Rolf, C., Franz, S.O., Lauer, T., Lehndorff, E., Frechen, M., Khormali, F., 2018. Late

547

Pleistocene dust dynamics and pedogenesis in Southern Eurasia -Detailed insights from the loess profile

548

Toshan (NE Iran). Quaternary Science Reviews 180, 85-95.

549 550

Yamazaki, T., Ioka, N. 1997. Cautionary note on magnetic grain-size estimation using the ratio of ARM to magnetic susceptibility. Geophysical Research Letters, 24, 751-754.

551

Yang, T.S., Hyodo, M., Zhang, S.H., Maeda, M., Yang, Z.Y., Wu, H.C., Li, H.Y., 2013. New insights into magnetic

552

enhancement mechanism in Chinese paleosols. Palaeogeography, Palaeoclimatology, Palaeoecology 369, 493–

553

500.

554

Zeeden, C., Hambach, U., Veres, D., Fitzsimmons, K., Obreht, I., Bösken, J., Lehmkuhl, F., 2017. Millennial scale

555

climate oscillations recorded in the Lower Danube loess over the last glacial period. Palaeogeography,

556

Palaeoclimatology, Palaeoecology. https://doi.org/10.1016/j.palaeo.2016.12.029.

557 558 559

Zhang, P., Lin, S., Ao, H., Wang, L., Sun, X., An, S., 2016. Rock Magnetism of the Offshore Sediments of Lake Qinghai in the Western China. Frontiers in Earth Science. https://doi.org/10.3389/feart.2016.00062.

Declaration of Interest

Hereby we declare that there's no financial/personal interest or belief that could affect our objectivity.

Sincerely Farhad Khormali