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Similarities among the Plio-Pleistocene terrestrial aeolian dust deposits in the World and in

ARTICLE in QUATERNARY INTERNATIONAL · APRIL 2011 Impact Factor: 2.13 · DOI: 10.1016/j.quaint.2010.09.011

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Similarities among the PlioePleistocene terrestrial aeolian dust deposits in the World and in Hungary

György Varga*

Geographical Research Institute, Hungarian Academy of Sciences, H-1112 Budapest, Budaörsi út 45, Hungary article info abstract

Article history: The widely distributed PlioePleistocene aeolian dust deposits are one of the most important terrestrial Available online 13 October 2010 archives of past climate and environmental changes. The alternation of loess and palaeosol layers is regarded as evidence of the cyclic nature of Pleistocene climate changes. The loess succession is underlain by aeolian red clay, which has been formed under warmehumid climates. According to the studies of red clayeloessepalaeosol sequences from China, Central Asia, Alaska, South America and Central , the mineral dust deposition has shown similar patterns since the Pliocene. The typical loess of the last one million years reflects glacialeinterglacial conditions, whereas the old loessepalaeosol sequences could be the product of shorter aridehumid climate cycles. The similarity of the sedimentary structures could be caused by the similar global climate conditions, controlled by orbital forcing. The investigated sections from Hungary (Central Europe) have been affected by local and regional geomorphological and climate factors. Even so, they can be correlated fairly well with the major global climate changes. The Hungarian aeolian dust deposits consist of three main groups of sedimentary formations: (1) PlioceneeEarly Pleistocene aeolian red clays, (2) the oldest loessepalaeosol sequences, formed from the almost continuous Early Pleistocene dustfall, and (3) the typical, glacialeinterglacial loess deposits of the last one million years, without remarkable dust deposition in the warmer periods. Ó 2010 Elsevier Ltd and INQUA. All rights reserved.

1. Introduction The loessepalaeosol sequences are widely considered as the most important terrestrial archive of Late Cenozoic climate changes. Mineral dust particles are entrained into the atmosphere by In the Carpathian Basin, after the desiccation of Lake Pannon, deflation of surface material from aridesemiarid areas. Today, the aeolian processes played a dominant role in the sedimentation. global annual input of mineral aerosols to the atmosphere is esti- Wind-blown loess and loess-like deposits cover more than half of mated to be between 1 and 2 billion t/y (Tegen et al., 1996). The this area, generally underlain by red clay. The stratigraphic rela- amount and the physical properties (e.g. grain-size) of these dust tionship between these two formations is still controversial in this particles response sensitive to environmental and climate changes. region. In China, analytical data have demonstrated that the Plio- These reactions have been caused by changes in the precipitation, cene red clay is also wind-blown in origin, and loess-formation was in the wind strength, in the regional moisture balance and in the caused by the higher sedimentation rate and the weaker pedogenic extent of dust source areas (Pye, 1987). processes (Ding et al., 1998). In some periods in the history of Earth, the global dust emission In the opinion of some authors (e.g. Pécsi, 1984), the very and the size and frequency of the dust storms have increased by limited amount of primary loess at the PlioePleistocene boundary several orders of magnitude, compared to the present situation (w2.6 Ma, Head et al., 2008) is explained by unfavourable palae- (Kohfeld and Harrison, 2001). The aeolian dust deposits (e.g. oclimatic, palaeogeographic conditions and the low amount of loessepalaeosol sequences, marine sediments, dust samples of ice mineral dust particles. However, it could be caused by the low cores), accumulated in these dusty intervals are one of the best stratigraphic preservation potential of loess sediments, being terrestrial archives of palaeoclimate and palaeo-environmental susceptible to reworking and redeposition by hydrological variations. processes. These old aeolian sediments are found in several loess regions (e.g. China e Liu et al., 1985; Ding et al., 1997, 2000; Lu e * Present address: Budaörsi út 45, H-1112 Budapest, Hungary. et al., 2001; Tajikistan Dodonov and Baiguzina, 1995; Ding et al., E-mail addresses: [email protected], [email protected]. 1999, 2002; Bronger, 2003;Alaskae Westgate et al., 1990; Beget

1040-6182/$ e see front matter Ó 2010 Elsevier Ltd and INQUA. All rights reserved. doi:10.1016/j.quaint.2010.09.011 G. Varga / Quaternary International 234 (2011) 98e108 99 et al., 2008; South America e Zárate, 2003; Rabassa et al., 2005; the input of the PCF is only one sample. The (generally) three EMMA and Central Europe e Fink and Kukla, 1977; Kukla, 1978; Kukla and end-members of the loess samples (Prins and Vriend, 2007; Prins Cílek, 1996; Tsatskin et al., 2001). et al., 2007) could represent the average dust grain-size distributions The purpose of this study was to summarize the current state of of three temporal aeolian sediment clusters of seasonal or other knowledge about the old loess deposits and the underlying aeolian short-term intervals. In case of loess deposits, the PCF populations sediments and to discuss the similarities of the PlioePleistocene probably illustrate the background and the local-derived dust aeolian sedimentation in Hungary and in the World. The loess components, and thus the process-related factors. The wind speed at sections were selected from Asia, Europe, North and South America, a given site also follows this continuous probability distribution, so so they represent global palaeo-environmental and palaeoclimate the grain-size distribution of wind-blown sediments should reflect conditions of the Late Pliocene and the Early Pleistocene. the transport agency (Sun et al., 2004). In this paper, due to many The wind-blown origin of the red clay is a crucial point in the single data, the PCF technique has been used. discussion of the dust deposits, because the climate became more According to this method the bimodal distribution curves can be arid after its formation around 2.6 Ma. The climate and the streng- interpreted as the sum of two overlapping Weibull functions (Sun thened dust flux could create suitable conditions for enhanced dust et al., 2002, 2004). accumulation and loess-formation. This increased dust-loading can ! be identified by the detailed grain-size analysis. a 1 a11 W1 þ W2 ¼ c1 a x b 1 1 a a 2. Materials and methods ð =b Þ 1 a a ð =b Þ 2 x 1 þ a =b 2 2 1 x 2 ; ð Þ e c2 2 2 x e 1 Several hundred samples from Hungarian loessepalaeosol and where a1 and a2 are the shape parameters, defining the kurtosis of red clay successions were collected, with special attention to old the curves (so the sorting), b1 and b2 are the location parameters, loess deposits. Samples were also taken from younger successions defining the position of the curves (so the grain-size), c1 and c2 are e from Hungarian stratotype sections (e.g. Paks, Basaharc, Mende weighting parameters. Fig. 1). The grain-size distribution of all samples was measured Iterative numerical methods were used to determine the loca- using a Fritsch Analysette 22 Compact laser grain-size analyzer, tion, shape and weight parameters as a least squares problem, and e m with 0.3 300 m measurement ranges in 62 channels. Using the to assess the appropriate goodness of fit of the measured to chemical extraction procedure described by Konert and Vanden- calculated data (Fig. 2). berghe (1997), organic material, carbonate and clay minerals can be The traditional statistical measures, such as mean, standard removed sequentially from the samples. After processing the deviation, skewness and kurtosis of the younger and older palae- samples with (10 ml, 30%) H2O2 and (10 ml, 10%) HCl to remove the osols could be very similar, but the detailed investigation of the $ organic material and the carbonate, 10 ml of 3.6% Na4P2O7 10H2O sedimentary units has shown interesting differences, using the was added to the samples in order to disperse the particles. The following formula: pedogenic component is colloidal and soluble material, with P P P fi 62 62 62 a small amount of super- ne particles, produced in pedogenesis x m ¼ x m x m ¼ i¼1 i i ¼ i 1 i f i þ i¼1 i ci ; (Paton, 1978; Bronger and Heinkele, 1990; Sun et al., 2004). d P c1 P c2 P (2) 62 m 62 m 62 m The granulometric parameters have been commonly used as i¼1 i¼1 i¼1 environmental indicators in sedimentary investigations. The grain- where d is the average grain-size, xi is the ith size-class of the 62 size distribution curves of most aeolian sediments are polymodal measuring channels, mi, mfi and mci are the weight percent of the and illustrate different transport and/or depositional processes particles in the sample, in the fine-grained population and in the (Sun et al., 2002), and can be interpreted as a mixture. coarse-grained population, and c1 and c2 are weighting parameters. The grain-size populations can be partitioned with different According to this formula the average grain-size is dependent on mathematic techniques, including parametric curve-fitting (PCF) the proportion and the grain-size of the components. and end-member modeling algorithm (EMMA e Weltje, 1997; Weltje and Prins, 2003; Vriend and Prins, 2005). The difference between the results of these two methods arises from their approach. Whereas the EMMA is based on the same time analysis of 3. PlioePleistocene aeolian dust deposits in Hungary: red clay the whole sequence based on the covariance structure of the dataset, and loess

Wind-blown loess and loess-like deposits are widely distributed in the Carpathian Basin, covering more than half of the area. Traditionally, based on its lithology, five main units have been UKRAINE distinguished. The DunaújvároseTápiósüly series and the Men- SLOVAKIA deeBasaharc series belong to the young loess sediments; the Paks I and Paks II series belong to the old loess sediments; and the oldest AUSTRIA 8 7 strata of the sequence is part of the Dunaföldvár series. This lowest 6 section consists of thin loess horizons between red (Mediterranean- HUNGARY type) palaeosols, reddish clays and loess-like deposits, underlain by 5 ROMANIA 4 red clay. SLOVENIA 2 3 The upper three series are more continuous and have more 1 SERBIA accurate numerical age data (Novothny et al., 2002, 2011), and thus can be correlated well with marine isotope stages (Gábris, 2007), 0 50 100 150 km and also with the Malan, Upper Lishi and partially with the Lower Lishi series in the Chinese Loess Plateau. The correlation with Fig. 1. Locations of the investigated and sampled sections. (1. Beremend, 2. Posta Valley (Pécs), 3. (red clay samples), 4. Szekszárd, 5. Paks, 6. Mende, 7. Basaharc, 8. regional sequences, e.g. Serbian loess deposits (Markovic et al., 2006, Dunaalmás). 2009), according to the stratigraphic similarities is also possible 100 G. Varga / Quaternary International 234 (2011) 98e108

7.0% 7.0% Measured grain-size Fitted distribution curves 6.0% Sample ID: Hid-1 6.0% R2 =0.99 Type: Red clay Fine component: 32.23% 5.0% Location: Hidas (Hungary) 5.0% Coarse component: 67.77%

4.0% 4.0%

3.0% 3.0%

Frequency

Frequency 2.0% 2.0%

1.0% 1.0%

0.0% 0.0% 0.10 1.00 10.00 100.00 1000.00 0.10 1.00 10.00 100.00 1000.00 a Grain-size (µm) Grain-size (µm)

7.0% 7.0% Measured grain-size Fitted distribution curves 6.0% Sample ID: Paks-03 6.0% R2 =0.99 Type: Young loess Fine component: 18.35% 5.0% Location: Paks (Hungary) 5.0% Coarse component: 81.65%

4.0% 4.0%

3.0% 3.0%

Frequency

Frequency 2.0% 2.0%

1.0% 1.0%

0.0% 0.0% 0.10 1.00 10.00 100.00 1000.00 0.10 1.00 10.00 100.00 1000.00 b Grain-size (µm) Grain-size (µm)

Fig. 2. Measured grain-size distribution and mathematically partitioned curves of (a) typical loess and (b) red clay samples.

(Novothny et al., 2011). These sediments can be regarded as the deposits, one steppe-type palaeosol and one pedocomplex. The typical, glacialeinterglacial loessepalaeosol successions. lower, 18 m part of the succession is significantly different. The The older loess and loessial sections in Hungary are known only reddish-yellow-pink colour, the compactness of the loess deposits, from some exposures and boreholes. Most of these profiles (except the reddish palaeosols, the frequent carbonate nodule beds and the the Beremend site) have been described in detail in previous large (30e40 cm) concretions make this section different from the studies (e.g. Pécsi et al. 1987; Pécsi and Schweitzer 1993, 1995). typical Late and Middle Pleistocene loess series. Here, attention is only drawn to some of the main characteristics Typical intensely weathered red clay can be found only as filling (Fig. 3). sediment in the fissures of the karstic limestone. Mineralogical The stratigraphical column of the borehole at Szekszárd (SW studies showed that the red palaeosols can be correlated with Hungary) consists of more than 90 m thick loess deposit interca- fissure filling deposits (Dezso} et al., 2007). This and other properties lated by 18 palaeosols. The lower 35e40 m of the section is situated (structureless, reddish colour, large carbonate concretions) suggest under the B/M boundary and it is composed of superimposed the old age of the succession, although there is no numerical age reddish palaeosols, underlain by red clay (Pécsi and Schweitzer, data. 1995). The lithological properties of the old loesses (reddish-yellow, The 60 m thick loessepalaeosol sequence in the Posta Valley structureless, smaller thickness of loess layers between red palae- (Pécs, SW Hungary) reflects the palaeoclimate conditions of the osols, large carbonate concretions) of these strata are very similar past 3e4 Ma, but due to the hiatuses in the section the recon- to other “ stony loess” series from e.g. Central Asia or China struction cannot be complete. The older horizons are generally (Wucheng loess). thinner compared to the upper part of the profile. The lower section The loessepalaeosol sections are generally underlain by red clay. consists of more than 30 units, largely reddish palaeosols and thin The red clay is situated on thick grayish-yellow, mica-rich, cross- loess strata. The lowermost sediments, red clays with calcareous bedded sand and sandy clay or locally on limestone. The lower part nodule beds, can be correlated with the red clays in the side of the of the sand unit contains a variety of fossils (e.g. bone fragments, Villányi Mountains, characterized by the Pliocene fauna (Pécsi et al., such as teeth, jaws, ribs of Hipparion sp., Mastodon sp., Rhinoceros sp. 1987; Pécsi and Schweitzer, 1993). and Sus sp.) with an age of w6Ma(Kovács, 2003; Fábián et al., 2008). At Dunaalmás (N Hungary), loess and reddish palaeosol deposits According to Schweitzer and Szöor} (1997), red clays can be have been identified enclosed in the travertine sequence. According subdivided into two compositional groups. The older (typical) red to the palaeomagnetic and palaeontologic studies, the age of the clays were formed under the warm, humid climate in the Pliocene. loessepalaeosol layers is more than 1.5 Ma. The section has The younger (reddish) clays can be correlated with the lowermost reversed magnetic polarity; expect the lowermost sandy loess layer red soils of the old loessepalaeosol successions. The detailed (Pécsi and Schweitzer, 1995). comparative studies, using optical microscopic and SEM analysis, The Beremend site in SW Hungary was investigated in detail. grain-size measurements, major- and trace-element geochemical The section situated on the southern foothill of the Villányi properties and geomorphological investigations have shown that Mountain, in an active limestone quarry. The almost 30 m thick the Hungarian red clays and the Chinese “Hipparion Red-Earth loessepalaeosol sequence was divided into two parts. A major Formation” have several similarities (Kovács et al., 2008). Although hiatus separates the younger and the much older, lower part of the without numerical age data the correlation could not be complete, series. The upper, 10 m thick section consists of pale yellow loess there are uncertainties. G. Varga / Quaternary International 234 (2011) 98e108 101

General Posta-valley Szekszárd Dunaalmás Beremend 0 description (Pécs) pale yellow, porous thickness: ~40 m Dunaújváros-Tápiósüly 10 loess pale yellow loess and 2 humous horizons sandy loess 5 forest steppe soils 7 steppe-type thickness: ~21 m thickness: ~10 m 20 palaeosols thick sandy loess and pale yellow loess Mende-Basaharc 1 sand layer loess layers sehnurB steppe-type soil 5 steppe-like soils brown earth complex 30 forest steppe soil sandy horizon erosional gaps brown earth complex Paks-I. thickness: ~30 m significant erosional sandy humous soil gaps 40 hydromorphous soil 5 brown forest soils 3 warmer forest 50 Paks-II. steppe soils

60

amayutaM )m(htpeD thin (reddish-yellow), thickness: ~20 m thickness: ~25 m silt, sandy loess and thickness: ~18 m compacted loess thin loess horizons thin loess horizons reddish palaeosol reddish-yellow loess 70 horizons Mediterranean-type reddish clays enclosed in the layers Dunaföldvár series Mediterranean-type red soils or reddish sand layers travertine sequence “stony loess“ layer 4 red palaeosols 80 red soils or reddish clay clays superimposed on significant erosional with Late- horizons each other gaps Villafranchian fauna large (30-40 cm) CaCO3 nodule beds 90

100

ssu silty red clay 110 prismatic structure thickness: ~5 m thickness: ~10 m aG typical red clay in the with slickensides red clay red clay horizons fissures of the karstic Red clay CaCO nodule CaCO3 nodule intercalated by CaCO3 120 3 Mesozoic limestone horizons horizons layers

trebliG 130

140 underlain by bentonite underlain by bentonite and Miocene sand and Miocene sand

Fig. 3. Generalized red clayeloessepalaeosol profile of Hungary and the main characteristics of the old loess sections from Hungary (based on Pécsi and Schweitzer, 1993, 1995).

4. Grain-size properties of the aeolian sequences show similarities to the younger palaeosols, whereas the typical grain-size of the red clays was rather different (Fig. 4). The grain-size distribution curves of the collected samples are mostly bimodal, representing two main sediment populations. The 5. Discussion coarse-grained component has been generally transported by surface winds in short suspension episodes, during the discontin- 5.1. Aeolian origin of the red clay in Hungary uous dust storms. The source of this coarse fraction was largely local material. The fine-grained component has been mainly The time of a considerable drop of the level of Lake Pannon can transported by upper level flow, and was deposited far from the be correlated with the lowering level of the source areas, probably reflecting the continuous background dust- during the Messinian Stage, and desert-like climate in the Carpa- load (Pye, 1987; Tsoar and Pye, 1987; Sun et al., 2002, 2004). thian Basin (Schweitzer and Szöor,} 1997). After the desiccation, the The possible factors which can modify the grain-size and could be aeolian sedimentation became more intensive. The accumulation of the cause of the secondary maximums are a second source area; the the aeolian dust deposits started around the ZancleanePiacenzian background dust-load; post-depositional weathering and pedogenic boundary, w3.6 Ma (Kovács et al., 2008). This period was charac- processes; and the dispersion of the silt- and sand-sized clay- terized by a warmehumid climate, with Southeast Asian faunal aggregates. According to Sun et al. (2002, 2004), Jeong et al. (2008) elements, like Viverridae, Pteromys, Ailuridae (Kretzoi, 1969, 1983; and Yang and Ding (2004) the role of pedogenic processes and the Jánossy, 1979). Although the climate was more humid compared to aggregation have restricted effect on the grain-size of the loess the previous stage, the amount of the mineral dust in the region samples. The super-fine (submicron) pedogenic particles could be was notable. Early scientists (Lóczy, 1886; Treitz, 1903; Sümeghy, removed in the chemical pre-treatment. However, in the case of the 1944) described the Hungarian red clay as a variety of the loess, palaeosols and red clay, the weathering could be more effective (Sun sediment formed by the deposition of wind-blown silt. The aeolian et al., 2006b). theory was attacked at the time, but has been confirmed by recent Using the parameters of the mathematically separated compo- research. Geomorphological properties, the blanket-like distribu- nents (Eqs. (1) and (2)) instead of the traditional statistical tion, the particle-size characteristics and micromorphological measures could be more useful to describe and analyze the investigations suggest that the main part of the red clay is wind- samples. The coarse population (16e63 mm) has positive skewness blown in origin (Schweitzer and Szöor,} 1997; Kovács, 2008; Kovács and leptokurtic kurtosis, the material is well sorted. The skewness et al., 2008, submitted for publication). of the fine-grained component (2e8 mm) is also positive, but the The detailed granulometric analyses of the red clays show simi- kurtosis is platykurtic, poorly sorted. The proportion of the fine- larity in terms of their bimodal grain-size distribution patterns with grained population is around 31e33% in the red clay samples, loess horizons, like in the Chinese Loess Plateau (Yang and Ding, 23e26% in the palaeosols, and 18e24% in the loess deposits. The 2004). Two main components can be distinguished from the curves. modal grain-sizes of the separated populations of the loess samples The different ratio of the fine- and coarse-grained populations in the 102 G. Varga / Quaternary International 234 (2011) 98e108

8.0% 8.0% Red clay: Red palaeosol or reddish clay: 7.0% Location: Hidas 7.0% Location: Beremend Sample ID: Hid-3 Sample ID: Ber-540 6.0% Fine: 31-33%; modal gs: 2.8-3.3 µm 6.0% Fine: 27-30%; modal gs: 3.1-3.7 µm

y Coarse: 67-69%; modal gs: 14-18 µm ycn Coarse: 70-73%; modal gs: 24-30 µm c 5.0% 5.0%

ne

eu

uqerF

4.0% qe 4.0%

r 3.0% F 3.0%

2.0% 2.0%

1.0% 1.0%

0.0% 0.0% 0.10 1.00 10.00 100.00 1000.00 0.10 1.00 10.00 100.00 1000.00 Grain-size (µm) Grain-size (µm)

8.0% 8.0% Palaeosol: Loess: 7.0% Location: Paks 7.0% Location: Paks Sample ID: Paks-008 Sample ID: Paks-012 6.0% Fine: 23-26%; modal gs: 3.8-5.3 µm 6.0% Fine: 18-24%; modal gs: 3.2-5.5 µm

ycneuqerF Coarse: 74-77%; modal gs: 27-31 µm y Coarse: 76-82%; modal gs: 28-33 µm 5.0% c 5.0%

neu

4.0% qer 4.0%

3.0% F 3.0%

2.0% 2.0%

1.0% 1.0%

0.0% 0.0% 0.10 1.00 10.00 100.00 1000.00 0.10 1.00 10.00 100.00 1000.00 Grain-size (µm) Grain-size (µm)

Fig. 4. Typical grain-size distribution curves and the mathematically separated populations of the aeolian dust deposits in Hungary. case of the red clays compared to the loess deposits could result from 5.2. Possibility of the loess-formation in the Early Pleistocene additional processes. The in situ weathering was more intensive during the Pliocene, but weaker wind systems or lower local dust One of the most important questions in the loess-formation accumulation-rates under a constant background dust-load also issue is the identification of physical processes that are responsible could result in more fine particle sedimentation. for the generation of fine-grained mineral material. Field studies, The Late Miocene deposits (conglomerates, sandstones, sands, experimental investigations and laboratory simulations have clays), eroded from the Eastern Alps and the local Messinian sands demonstrated that not only the glacial grinding can convert large could be the source material of the coarse sediment population of quantities of sand-sized or even larger quartz particles into silt- the red clays (Kuhlemann et al., 2002; Kovács et al., 2008). The sized fragments (Wright, 2001a). The role of other processes (e.g. source area of the fine, background (clay- and fine silt-sized) frost weathering, salt weathering, fluvial comminution, aeolian material is yet to be fully explored. The Carpathian Basin located in abrasion) is also significant in the production of dust material (Pye, the D1b zone at the “Saharan dustfall map” from Stuut et al. (2009), 1987, 1995; McTainsh, 1987; Smalley, 1995; Assallay et al., 1998; meaning that the Saharan dust material could be incorporated into Wright, 2001b; Smith et al., 2002). the soil system and serve to increase the fine silt content (Stuut After the formation of the red clay, the climate in the Carpathian et al., 2009). Since 1991, approximately 50 episodes of Saharan dust Basin became more arid. The closed forests were replaced by open intrusion have been observed in the Carpathian Basin (Borbély-Kiss vegetation with Late Villanyian (Middle Villafranchian) ostrich and et al., 2004; Szoboszlai et al., 2009), and this is the present situation, giraffe in the fauna (Kretzoi, 1969, 1983). The rate and the frequency which is a less dusty interval in the region. of the dust-falling episodes increased in the warm semi-desert The connection between large scale atmospheric patterns (El environment. Niño Southern Oscillation, North Atlantic Oscillation) and the Similarly to the red clay, the main part of the material of the loess quantity of Saharan dust is controversial. According to Prospero and could originate from local sources. The enhanced erosion in the Lamb (2003), major dust outbreaks could be associated with major mountain areas (Alps, Carpathians), around the onset of the Northern El Niño events. During the Pliocene a permanent El Niño-like state Hemisphere glaciation produced enormous amount of unconsoli- (El Padre) has influenced the climate conditions (Ravelo et al., dated sediments (Kuhlemann et al., 2002), and almost w100,000 km3 2006; Shukla et al., 2009), so the Saharan dust outbreaks could be material was supplied by the rivers (Újvári et al., 2008)and/orbythe dominant factors of the sedimentation in the Carpathian Basin. westerlies into the Carpathian Basin (Kovács et al., 2008). Since 5 Ma, Sahara has been the main dust source area. Aeolian The grain-size distribution curves of loess deposits show strong dust material from Africa can be found in the Mediterranean and similarity with the red clays. The bimodal pattern could also be Atlantic marine sediments (e.g. Wehausen and Brumsack, 1998; identified, indicating that two sediment populations have been deMenocal, 2004), in the Terra Rossae around the Mediterranean involved in the loess-formation. Under the warm, arid conditions Sea (Yaalon and Ganor, 1973), and even at Bermuda (Herwitz et al., and open vegetation cover, the river-supplied floodplain-sediments 1996). Thus, its effect is global and very significant (Goudie and together with other local, loose granular deposits could be the main Middleton, 2006). source material of the proximal, coarse sediment population. The G. Varga / Quaternary International 234 (2011) 98e108 103

fine-grained populations in the grain-size distribution curves of and the higher wind speed have resulted in higher mass accumu- loess deposits have a lower percentage, compared to the red clay lation rate and higher modal grain-size for each sediment pop- samples. This suggests that the proximal mineral material may ulations. Throughout the moister phases, the grain-sizes have been have played much larger role in the sedimentation than did the reduced by the weaker winds, and the amount of the local loose background dust. However, this does not mean that the amount of material has been also decreased. The palaeo-environmental and the distal dust material was reduced, but the increased quantity sedimentary data suggest that the formation of the old loess has of the local material caused a decrease in the relative proportion of been influenced by the Early Pleistocene changes in the moisture the fine-grained particles. The source area of the fine sediment balance rather than by classical glacial conditions. population is still controversial, but Saharan dust outbreaks could have played an important role in the supply of the clay and very- 5.3. The oldest loess sequences of the World fine silt-sized material into the Carpathian Basin. The old loess series are intercalated by red palaeosols or reddish 5.3.1. Chinese Loess Plateau clays. In the younger palaeosols the proportion of the fine-grained In China, loess covers an area of w450,000 km2 on the Loess components is higher compared to the underlying loess units, but Plateau, in the middle reaches of the Yellow River. The maximum the modal grain-size of the sediment populations is almost iden- thickness is more than 400 m, but over most of the plateau 150 m is tically. While, the fine-coarse ratio of the old, reddish palaeosols typical (Liu et al., 1985). During glacial periods the growth of conti- was very similar to the loess units, the lower grain-size was caused nental ice sheets and the intensification of the winter monsoon by the lower modal grain-sizes of the sedimentary components. resulted in the expansion of the inland deserts and high atmospheric Based on the detailed granulometric analysis, the red palaeosols dust influx, leading to loess deposition. The aeolian sedimentation can be interpreted as transitional types between the red clays and rate was reduced during interglacial periods, when the summer the loessepalaeosol deposits. monsoon was the dominant, which permitted soil to develop (Ding According to these granulometric properties (Fig. 5), the young et al., 2000). On the basis of their ages and lithological features, the palaeosols could be formed completely from the underlying loess loessesoil successions can be divided into five units: the Potou, the deposits of the former glacial periods, and there was no interglacial Malan, the Upper Lishi, the Lower Lishi and the Wucheng loess series. dust deposition or it could be neglected. The various grain-size The last two units belong to the old loesses (Liu et al., 1985). The characteristics of the old loesses and palaeosols reflect a largely colour and the structure of the old loess are different from the different depositional system. The differences in the modal grain- younger loess deposits. These layers are darker, the oldest part is sizes show that the parent material of the red palaeosols could not nearly reddish-brown or red and the structure is more massive with originate from the underlying loess successions. These reddish large carbonate concretions and calcareous nodule beds. The thick- layers have been formed as vertically accreted soils direct from the ness of the palaeosols is relatively less, and only thin loess layers wind-blown dust. separate them. Generally, aeolian red clay can be found under the old The Early Pleistocene warmearid and warmesubhumid small- loess (Ding et al., 1997, 1998; Lu et al., 2001; Sun et al., 2004). amplitude oscillations were suitable for almost continuous dust Therefore, the loess layers can be regarded as the continuation of the deposition. During the arid periods, the reduced vegetation cover atmospheric dust deposition. The shift from the red clay to the loess

7.0% 7.0%

MoL-coarse = Mo PS-coarse 6.0% 6.0%

5.0% 5.0%

4.0% 4.0%

3.0% 3.0% MoL-fine = Mo PS-fine

Frequency Frequency 2.0% 2.0%

1.0% 1.0%

0.0% 0.0% 0.10 1.00 10.00 100.00 1000.00 0.10 1.00 10.00 100.00 1000.00 a Grain-size (µm) Grain-size (µm)

7.0% 7.0% MoL-coarse > Mo PS-coarse 6.0% 6.0%

5.0% 5.0%

4.0% 4.0%

3.0% 3.0% MoL-fine > Mo PS-fine

Frequency Frequency 2.0% 2.0%

1.0% 1.0%

0.0% 0.0% 0.10 1.00 10.00 100.00 1000.00 0.10 1.00 10.00 100.00 1000.00 b Grain-size (µm) Grain-size (µm)

Fig. 5. The modal grain-size values of the mathematically separated sediment populations show differences of the (a) younger palaeosols and the (b) old, red palaeosols (or reddish clays) in Hungary. 104 G. Varga / Quaternary International 234 (2011) 98e108

80°

Red Hill loess Age: 1.5-2 Myr Roxolany-N. Etuliya Age: more than 1.5 Myr 60° Krems-Stranzendorf loess Age: 2.5-3 Myr Gold Hill loess Age: 3 Myr 40° Chasmanigar loess Age: 2-2.5 Myr Tarim Basin Age: 5 Myr Wucheng loess 20° Age: 2.6 Myr

0°

20°

40° Pampean loess Age: 2-2.5 Myr

60°

150° 120° 90° 60° 30° 0° 30° 60° 90° 120° 150° 180°

Fig. 6. Schematic map showing loess distribution around the World and the oldest loess deposits (after: Pécsi, 1990; Muhs and Bettis, 2003).

is approximately at the M/G palaeomagnetic boundary, around (Dodonov and Baiguzina, 1995; Ding et al., 2002). While the Chinese 2.6 Ma. This time was the onset of the glaciation of the Northern loessesoil layers reflect the variation of the East Asian monsoon, the Hemisphere (Shackleton et al., 1984). The stronger northwesterly alternations in the Tajik aeolian sequences were caused by the wind and the coldearid climate resulted in a higher sedimentation varying westerlies. During interglacial periods the precipitation has rate and weaker pedogenesis (Ding et al., 1997; An, 2000). been supplied by the moisture-laden Mediterranean cyclones. In the glacial times the penetration of the moist westerly air-masses 5.3.2. Tarim Basin was blocked by the northern winds from the European Ice Sheet One of the major mineral dust source areas of the Chinese loess (Dodonov and Baiguzina, 1995). The loessepalaeosol sequences in is the Taklimakan Desert in the Tarim Basin (Liu et al., 1985). Early southern Tajikistan (Chashmanigar, Karamaydan) recorded the studies suggest that the Taklimakan was formed in the Middle oscillation of dry and wet periods, rather than cold and warm Pleistocene (Zhu, 1981), but according to the detailed analysis of the stages. According to palaeomagnetic, palaeontologic, and micro- buried aeolian sands this age is heavily underestimated, and the mophologic investigations, and correlations of the marker horizons area became desert in the Late Miocene (Dong et al., 1991; Zheng with well-known Chinese loess sequences, the dust accumulation et al., 2000). This period was the onset of the red clay formation in and the loess-formation in Central Asia started around 2e2.5 the main part of the Loess Plateau, with material originating partly million years ago (Dodonov and Baiguzina, 1995). The thickness of from the Tarim Basin. The 5000 m thick continuous molassic this dust deposits reaches 180e200 m (e.g. at Chashmanigar). The sediments in the southern part of the Tarim Basin have recorded upper part of the Chashmanigar section consists of 10 well-devel- the uplift history of the Tibetan region and the palaeo-environ- oped soils, separated by 3e12 m thick loess horizons. In the lower, mental conditions since the Miocene. Aeolian siltstones or loess older part, the reddish palaeosols are intercalated by thin loess sediments have been preserved as intercalated bands and lenses in layers or only by carbonate nodule horizons. This structure is very these molassic deposits (sandstones, sandy mudstones, conglom- similar to the Chinese Wucheng loess, suggesting that the balance erates). The old loess layers in the Artux and Xiyu Formations show between the two competing processes, loess deposition and pedo- very similar grain-size distribution patterns with the typical genesis, varied similarly to the Chinese episodes (Bronger, 2003; Pleistocene Xinjiang Group loess (Zheng et al., 2003). So, the Dodonov, 2005). loessial sedimentation started around 5 Ma in the Tarim Basin. It could be correlated with the red clay formation in the Loess Plateau, 5.3.4. Gold Hill Loess, Alaska (USA) but due to the closer source area and the higher aridity, the dust Late Cenozoic fine-grained deposits are common in Alaska, accumulation led to loess-formation in the foreland basins of the especially in the valley of the Tanana and Yukon Rivers. Péwé (1951) Kunlun and Altyn Plateau. was the first who recognized that the silt material of these sedi- ments is aeolian in origin, and can be considered as loess. As this 5.3.3. Tajikistan, Central Asia area occurs within the zone of influence of volcanoes, there are After the Chinese Loess Plateau, the second most extensive several tephra beds originating from the Aleutian Arc and the loessepalaeosol successions can be found in Tajikistan, Central Asia Wrangell Volcanic Field. Fission-track dating studies show that the G. Varga / Quaternary International 234 (2011) 98e108 105

Fig. 7. Correlation of the PlioePleistocene loessepalaeosol sequences. age of the oldest tephra layer (PA tephra bed located w11 m from Formation (the lower part of the so-called Pampean sediments e the bottom of the loess section) is 2.02 Ma (Westgate et al., 2003). Bidegain et al., 2009) is probably the oldest South American The loess units are intercalated by several palaeosols (e.g. Eve loessepalaeosol succession, made up of loess layers, reddish Creek, Dawson Cut Forest Bed), which were formed during inter- palaeosols and carbonate accumulation horizons, and concretions. glacial periods. The mass accumulation rate of these loess sections The age of these sediments, based on magnetostratigraphic and is very low compared with other sections from the World. In the palaeontologic investigations is about 2e2.5 Ma (Rabassa et al., absence of numerical age data on the lower loess unit, the teph- 2005). rochronology, the palaeomagnetic investigations and the low mass accumulation rate suggest that the deposition of the loess material 5.3.6. Central European old loess deposits began w3Ma(Westgate et al.,1990; Beget,1996; Beget et al., 2008). Sequences of loess deposits with interbedded soils along the bluffs and terraces of Central European rivers provide a detailed 5.3.5. Pampean Loess, South America Late PlioceneePleistocene climate archive of the area. The aeolian PlioePleistocene aeolian dust deposits cover over an area of sediments at KremseStranzendorf (Austria) and at Cerveny Kopec about 1 million km2 in the South American Pampas and in the (Czech Republic) can be designated as the oldest loess deposits in Argentinean Chaco (Iriondo, 1997). Glacialeinterglacial variations the region (Kukla and Cílek, 1996). The corridor position in the non- dominated the climatic conditions from the Miocene to the Pleis- glaciated region between the Fennoscandinavian ice sheet and the toceneeHolocene boundary. The aeolian sedimentation started Alpine glaciers could explain the very detailed and complete around 10 Ma, but the palaeogeographic conditions were not suit- preservation of the climate history in the loessepalaeosol succes- able for loess-formation from the accumulated dust (Zárate, 2003). sions. The B/M boundary can be found in the upper part of the Traditionally, these sediments have been called loess-like, loessoid, Krems site, in the loess horizon between the KR4 and KR5 palae- loessic deposits or secondary loesses. Even the old (4e5 Ma) silty osols, while the three red sub-Mediterranean soils at the bottom aeolian sequences, with abundant remains of vertebrate fossils from belong to the Gauss Chron. Thus, the loessepalaeosol profile at the Chapadmalalan stage along the Mar del Plata sea-cliffs cannot be Krems completed with the drilling data from Stranzendorf, fully regarded as loess. The sedimentary record consists of palae- stretches back to 2.5e3Ma(Fink and Kukla, 1977). osols, calcrete crusts, carbonate nodules and thin loess layers. The loess layers at Cerveny Kopec, covering five alluvial terraces According to Rabassa and Coronato (2009), the climate of of the Svrtka River in the easternmost foreland basin of the Alps Patagonia became colder w2.5 Ma, and this glacial environment provide information about palaeo-environmental conditions since could be more suitable for loess-formation. The Ensenada the Early Pleistocene. Kukla (1978) has compared the sequence 106 G. Varga / Quaternary International 234 (2011) 98e108 with oxygen-isotope stages and distinguished 11 glacial cycles in the carbonate nodule beds in the sections reflect these short-term the profile. oscillations. The almost constant grain-size, the many carbonate Thick loessepalaeosol sequences can be found on the old nodule horizons and the colour variations in the red clay reflect the terraces of the Lower Danube and Dniester rivers in the Western Pliocene low-amplitude (19e23 kyr), precession-related cycles. Black Sea region (Veklich, 1979; Gendler et al., 2006). The loess According to deMenocal (2004), the quantity and frequency of the record at Roxolany and Novaya Etuliya stretches back to at least Saharan dust outbreaks also followed these short-term climate 1.5 Ma (Tsatskin et al., 2001). The underlying subaerial layers, changes in the Pliocene. intercalated by red soils and the lower part by red clay were formed The formation of the oldest loess deposits started around 2.6 Ma. also from aeolian dust. The lower palaeosols are well-developed This period was the onset of the glaciation on the Northern Hemi- Mediterranean soils, upward the sequence consists of forest soils, sphere (Shackleton et al., 1984) and the acceleration of the uplift in forest-steppe soils and chernozems, indicating gradual decrease of mountain areas such as the Tibetan Plateau (Ruddiman and Kutz- the precipitation since 4.6 Ma to the Holocene. The B/M boundary is bach, 1989) and other Central Asian mountain ranges (Bullen et al., situated around the PK7 quadruple pedocomplex, called “Roxolany 2001), the Alaska Range (Fitzgerald et al., 1993) and the Andes loessesoil suite” (Faustov et al., 2009). Below the palaeomagnetic (Jordan et al., 1983; Strecker et al., 1989). The causal relationship reversal, the sequence at Novaya Etuliya consists of six between the Late Cenozoic climate changes and the uplift of loessepalaeosol couplets. The oldest Danube terrace (XII) can be mountain ranges is still disputable (Molnar and England, 1990; Hay found under the loess section, with Khaprovian faunal complex, et al., 2002; Kuhlemann et al., 2002; Whipple, 2009). which age is almost 2.5 Myr (Nikiforova, 1997). 6.2. PlioePleistocene aeolian dust deposits 6. Conclusions PlioePleistocene aeolian dust deposits are widely distributed in 6.1. Possible causes of the similarity of the PlioePleistocene aeolian the World, recording the palaeo-environmental and palaeoclimatic dust depositional patterns conditions at least of the last 3.5 Myr. According to the studies of marine sediments and red clayeloessepalaeosol sequences, the As a consequence of the above-mentioned profiles, the oldest amount of the aerosolic mineral dust has risen around the onset of loess sequences of the World have some very similar properties the Northern Hemisphere glaciation. This period could be the (Figs. 6 and 7). The reddish-yellow colour, the structureless nature, beginning of the loess-formation in several places, due to the the smaller thickness of loess layers between the red palaeosols, enhanced quantity of silt-sized material and the suitable environ- the large carbonate concretions and the age of the oldest loess mental conditions. horizons are common features of the old loess deposits. These The wind-blown sequences (red clay, loess-like or loessoid lithological and stratigraphic characteristics are fairly different sediments), underlying the oldest loess deposits suggest that the from the pale yellow, porous, “typical” loess of the last about one aeolian processes were dominant factors in the sedimentation also million years (Pécsi, 1984). The aeolian sediments (red clay, loess- in former periods. The loess layers can be regarded as the like, loessoid deposits) underlying the old loess were formed also continuation of the atmospheric dust deposition. Recent investi- from falling-dust, but due to the palaeogeographic conditions and/ gations of the red clay in the Carpathian Basin show that the main or the low amount of mineral dust material, loess-formation was part of the material is wind-blown in origin (Kovács, 2008; Kovács obstructed in that period. et al., 2008). These results have been confirmed during the The red clayeloessepalaeosol record in the Chinese Loess detailed granulometric analysis of present work. The grain-size Plateau indicates that the dust deposition started at least w7.2 Ma in distribution curves of the red clay indicate similar depositional the area (Sun et al., 1998). Dust record of the ODP 885/886 site processes to the loess. (North Pacific Ocean) shows strong similarity in terms of their mean According to the particle-size characteristics of the old linear sedimentation rate pattern, indicating a period of increasing loessepalaeosol sequences, frequent, small-amplitude climatic dust production in the inner part of the Asian continent (Rea and oscillations have been archived in the Early Pleistocene loess and Hovan, 1995; Rea et al., 1998; Sun et al., 2006a). During the loess-like layers. The smaller thickness of the loess horizons indi- warmemoist Pliocene climate, the extent of the source areas and cates that the episodes of loess-formation were shorter than in the the dust accumulation-rates were smaller, while the post-deposi- Middle and Late Pleistocene, but the palaeosols could be formed also tional pedogenic processes were stronger as compared to the direct from the falling-dust. This phenomenon could be consistent Pleistocene conditions. The shift from this moist and warm climate with the orbital forced climate dynamics, so the thin loess layers can to a more arid one allowed the formation of the oldest loess deposits be interpreted as the result of the short-term, 41 kyr cycles, which around 2.6 Ma. were the dominant before the Middle Pleistocene revolution. According to the spectral analysis of marine sediments and Chinese loess deposits, the amount of the deposited mineral dust Acknowledgements material varied with the Earth’s orbital parameters. In the Pliocene, e the 19 23 kyr precessional cycles were the dominant. At about the The author wishes to express his deepest thanks to Dr. János w e onset of the Northern Hemisphere glaciation ( 2.6 2.8 Ma) the Kovács from the Department of Geology, University of Pécs and to fi obliquity-related 41 kyr cycles can be identi ed as the main factor, Prof. Ferenc Schweitzer from the Geographical Research Institute and about 1 Ma the 100 kyr cycles became the prominent (Raymo Hungarian Academy of Sciences for suggestions. Dr. Ágnes Novothny et al., 1997; Liu et al., 1999; deMenocal, 2004; Lisiecki and Raymo, and an anonymous reviewer are thanked for their constructive 2005, 2007). comments and suggestions. I am also grateful to Prof. Norm Catto for The loess layers and also the palaeosols of the last 1 Myr language improvement. demonstrate that the loess-forming processes increased in response to the pronounced warmecold 100 kyr cycles (Dodonov, References 2005). 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