Quaternary Loess-paleosol Sequence Research Articles

The usefulness of the magnetic susceptibility of loess paleosol sequences for paleoclimate and stratigraphic studies: The case of the Quaternary Palouse loess, northwestern United States

Worldwide, Quaternary loess-paleosol sequences archive terrestrial paleoenvironmental information. The Palouse loess in the northwestern USA is one such deposit representing at least a million years of sediment accumulation. Loess paleosol sequences are often studied via the magnetic susceptibility of sediments and the changes in susceptibility with depth. However, since variations in magnetic susceptibility can have different underlying causes, the interpretation of the magnetic susceptibility of loess depends on factors specific to each major loess region. We measured the magnetic susceptibility of sediments along depth profiles in a well-studied exposure of the Palouse loess in eastern Washington, USA (the “CLY-2 site,” 46.3131° N, 118.4874° W, WGS84). Our measurements show that the magnetic susceptibility of sediments in the Palouse loess varies systematically and predictably with depth and can be correlated with other magnetic susceptibility profiles at the outcrop scale and at the regional scale. We also measured changes in grain size, elemental abundance, mineralogy, and other magnetic properties to determine the most likely cause of the magnetic susceptibility signal. Based on these results, variations in magnetic susceptibility in the Palouse are likely driven mostly by changes in coarse sediment supply and accumulation of tephra rather than changes in weathering. Magnetic susceptibility is useful as an inexpensive, non-destructive tool for stratigraphic correlation of Quaternary loess deposits in the Palouse, especially in combination with paleosol stratigraphic markers and known tephra deposits.

Iron oxide characteristics of the Chinese loess-red clay sequences and their implications for the evolution of the East Asian summer monsoon since the Late Oligocene

The most significant climatic change in East Asia involved the formation and evolution of the coupled monsoon-arid environmental system during the Cenozoic, which was dynamically linked to global cooling and the growth of the Qinghai-Tibet Plateau. However, our understanding of monsoon evolution since the Late Oligocene remains controversial due to differences in the interpretation of various environmental proxies from loess archives. In this study, the composition and relative abundance of pedogenic iron oxides of two eolian sequences from the Lingtai section and the Zhuanglang drill core were investigated using rock magnetic, optical spectroscopy, and geochemical analyses. The results indicate that while the composition of iron oxides in the Mio-Pliocene red clay and Quaternary loess-paleosol sequences is similar, the concentrations of magnetite, maghemite, hematite and goethite are quite different between loess, paleosol and red clay. The combination of magnetic proxies (magnetic susceptibility, Fed/Fet, and color a* values) reveals that precipitation and temperature played varying roles in driving pedogenesis and chemical weathering since the Late Oligocene. During the Late Oligocene to Early Miocene, the occurrence of relatively strong pedogenesis and chemical weathering was likely the result of high temperatures rather than high precipitation. The East Asian summer monsoon intensified during the Middle Miocene Climate Optimum (16.5–14.5 Ma), in response to global climatic warming; subsequently, during the Middle to Late Miocene, the monsoon intensity gradually weakened due to global cooling. After ~8 Ma, the summer monsoon strengthened substantially and reached a maximum during 4.5–2.6 Ma, possibly as a result of the uplift of the northeastern margin of the Qinghai-Tibetan Plateau during the Late Miocene. The monsoon intensity then commenced a decreasing trend in the Early Pleistocene, but then strengthened again after ~1.0 Ma.

Geochemistry of a Late Quaternary loess-paleosol sequence in central Argentina: Implications for weathering, sedimentary recycling and provenance

A loess-paleosol sequence in the Pampean Plain, central Argentina was analyzed geochemically, in order to evaluate the weathering signature and sedimentary recycling as well as to analyze the origin of these loessic sediments. Corralito I sequence is composed of three paleosols and a buried soil separated by loess layers. The loess-paleosol sequence shows a similar geochemical composition throughout, suggesting that pedogenesis has not been intense enough to mask the chemical signature of the parent material. Weathering indices (CIA, CIW, PIA and LWI), elemental ratios (Rb/Sr, CaO/TiO2 and Na2O/TiO2), and the A-CN-K ternary diagram indicate incipient chemical alteration for this sequence, compatible with a weathering-limited regime. As expected, paleosols (CIAs ~60) exhibit a slightly higher chemical alteration than loess layers (CIAs ~58). Mass balance calculations reveal the losses of some major oxides (i.e., CaO, Na2O) and Sr in the buried soil and paleosols compared to its loess mantles, reflecting the weathering of plagioclase. Besides, the losses of K2O and Ba in the buried soil and paleosols I and II, when compared to its loess layers, suggest the chemical alteration of K-feldspar. The chemical alteration of volcanic glass is evidenced by the relative losses of As in almost all levels. Conversely, the relative gains of Fe2O3 and MgO reveal that pyroxenes and amphiboles or Fe oxy-hydroxides are concentrated in paleosols and the buried soil compared to its loess mantles. The geochemical approach used to constrain the origin of these Pampean Plain loessic sediments indicates they derive mainly from the Andean region. Conversely, the Pampean ranges, the Paraná River basin and Uruguayan Precambrian outcrops, which were pointed out as minor local sources, do not contribute significantly to the loess deposits. This work also shows that Corralito I loess-paleosol sequence and other loess samples from Argentina do not evidence sedimentary recycling, suggesting that these Pampean Plain loess deposits are mainly composed by young materials derived from undifferentiated volcanic rocks.

Quaternary loess-paleosol sequences in East and Central Asia in comparison with Central Europe – micromorphological and paleoclimatological conclusions

Quaternary loess-paleosol sequences in East and Central Asia in comparison with Central Europe – micromorphological and paleoclimatological conclusions

Magnetostratigraphic dating of the Linyi Fauna and implications for sequencing the mammalian faunas on the Chinese Loess Plateau

AbstractThe Chinese Loess Plateau (CLP) in North China is an important terrestrial archive that witnessed the environmental changes and mammal and early human evolution in Asia over the past 2.6 Ma. Establishing precise ages for the Pleistocene faunas on the CLP is critical for better understanding of these environmental, biological, and archaeological issues. Here we report a new magnetostratigraphic record that places age constraints on the Linyi Fauna on the southeastern CLP. Our investigated 170-m-thick Linyi section mainly consists of two portions: (1) an overlying eolian Quaternary loess-paleosol sequence and (2) underlying fluvial-lacustrine sand and silty clay. Paleomagnetic results suggest that the composite section records the Brunhes chron, Jaramillo and Olduvai subchrons, and successive reverse polarity portions of the intervening Matuyama chron. The Linyi Fauna is located between Jaramillo and Olduvai subchrons in the fluvial-lacustrine interval, with an estimated age of ~1.5–1.6 Ma. Combining previously dated faunas, we establish a Pleistocene magnetochronology spanning from 2.54 to 0.65 Ma for the faunas on the CLP.

Mineral magnetic record of the Miocene-Pliocene climate transition on the Chinese Loess Plateau, North China

AbstractPre-Quaternary terrestrial climate variability is less well understood than that during the Quaternary. The continuous eolian Red Clay sequence underlying the well-known Quaternary loess-paleosol sequence on the Chinese Loess Plateau (CLP) provides an opportunity to study pre-Quaternary terrestrial climate variability in East Asia. Here, we present new mineral magnetic records for a recently found Red Clay succession from Shilou area on the eastern CLP, and demonstrate a marked East Asian climate shift across the Miocene-Pliocene boundary (MPB). Pedogenic fine-grained magnetite populations, ranging from superparamagnetic (SP)/single domain (SD) up to small pseudo-single domain (PSD) sizes (i.e., from <30 nm up to ~1000 nm), dominate the magnetic properties. Importantly, our mineral magnetic results indicate that both pedogenic formation of SP grains and transformation of SP grains to SD and small PSD grains accelerated across the MPB in the Shilou Red Clay, which are indicative of enhanced pedogenesis. We relate this enhanced pedogenesis to increased soil moisture availability on the CLP, associated with stronger Asian Summer Monsoon precipitation during an overall period of global cooling. Our study thus provides new insights into the Miocene-Pliocene climate transition in East Asia.

Tectonic uplift-influenced monsoonal changes promoted hominin occupation of the Luonan Basin: Insights from a loess-paleosol sequence, eastern Qinling Mountains, central China

Quaternary soil deposits from northern and southern China are distinctly different, reflecting variability of the East Asian monsoon north and south of the Qinling Mountains. Coeval sediments from the transitional climatic zone of central China, which are little studied to date, have the potential to improve our understanding of Quaternary monsoon changes and associated influences on hominin occupation of this region. Here, we investigate in detail a well-preserved and continuous Quaternary loess-paleosol sequence (Shangbaichuan) from the Luonan Basin, using a variety of weathering indices including major and trace element ratios, clay mineralogy, and Fe-oxide mineralogy. The whole-rock samples display similar rare earth element patterns characterized by upper continental crustal ratios: (La/Yb)N ≈ 9.5 and Eu/Eu* ≈ 0.65. Elemental data such as (La/Yb)N, La/Th and Eu/Eu* ratios show a high degree of homogeneity, suggesting that dust in the source region may have been thoroughly mixed and recycled, resulting in all samples having a uniform initial composition. Indices for pedogenic weathering such as Na/K, Ba/Sr, Rb/Sr, CIA, CIW, CPA, PIA, kaolinite/illite, (kaolinite + smectite)/illite, and hematite/(hematite + goethite) exhibit similar secular trends and reveal a four-stage accumulation history. The indices also indicate that the climate was warmer and wetter during the most recent interglacial stage, compared with coeval environments of the Chinese Loess Plateau. Secular changes in weathering intensity can be related to stepwise uplift of the Qinling Mountains and variation in East Asian monsoon intensity, both of which played significant roles in controlling climate evolution in the Luonan Basin. Furthermore, intensified aridity and winter monsoon strength in dust source areas, as evidenced by mineralogic and geochemical changes, may have been due to the mid-Pleistocene climate transition. Based on temporal correlation of warmer and wetter climatic conditions with more frequent hominin occupation, we infer that the paleoclimate in the eastern Qinling Mountains remained mild and favorable during glacial stages of the Late Quaternary, thus promoting early human settlement.

U-Pb ages of detrital zircon and provenances of Red Clay in the Chinese Loess Plateau

The Chinese Loess Plateau (CLP), which is located in the central part of China, mainly contains two sequences: the Quaternary loess-paleosol sequence and the late Miocene-Pliocene Red Clay sequence. U-Pb ages of detrital zircon from the Quaternary loess-paleosol sequences indicate that the current spatial pattern of central Asian aridification was largely established during the early Quaternary. U-Pb ages of detrital zircon from the underlying Red Clay sequences demonstrate that the northern source regions were important contributors for the dust since the late Miocene, except for the periods of ∼8Ma and ∼5.5 to ∼4Ma. These two periods correspond to increased and decreased dust deposition in the North Pacific, respectively, ascribed to the late Miocene aridification of the Qaidam Basin (in the west of the CLP) and the early Pliocene aridification of the Tarim Basin (in the west of the CLP). We attribute the increase of the Qaidam Basin-derived North Pacific dust fluxes to the uplift of the NE Tibetan Plateau. Such uplift also controlled the climatic and environmental changes in central Asian during the late Miocene. This study highlights the dynamical process of the central Asian aridification during the late Miocene-Pliocene.

Zircon U-Pb Ages of Quaternary Loess-Paleosol Sequences from the Luochuan Section: Implication for Sediment Provenance

Zircon U-Pb Ages of Quaternary Loess-Paleosol Sequences from the Luochuan Section: Implication for Sediment Provenance

Micromorphological investigations of the Late Quaternary loess–paleosol sequences of the Kashmir Valley, India

The loess–paleosol sequences of the Karewa Group preserve a valuable repository of the Late Quaternary climatic changes and the landscape evolution history of the Karewa Basin of Kashmir Valley in their lithological and pedogenic records. Three representative loess–paleosol sections at Shankerpora (SP), Khan Sahib (KS) and Pattan (PT) localities were chosen for detailed lithostratigraphic fieldwork and micromorphological observations of thin sections. Lithostratigraphic analysis revealed lateral and vertical variation in thickness and number of paleosol profiles from south-west to north-west of the Karewa Basin suggesting the availability of land-surface for periodic loess deposition. The SP section is marked by 6 (SP-S6, S7, S8, S9, S10, S12), KS section by 3 (KS-S2, S4, S5) and PT section by 2 (PT-S1, S3) thick mature paleosol profiles. Theses paleosols have well developed ‘Ah’ and ‘Btk’ horizons representing prolonged land-surface stability when pedogenic processes outpace loess deposition. On the other hand comparatively thin to thick paleosol profiles represent weak to moderate pedogenic maturity indicating short stratigraphic breaks with rapid loess deposition. Micromorphological observations of thin sections suggested that clay illuviation and CaCO3 accumulation have operated within the paleosol profiles. CaCO3 features are often associated with clay coatings suggesting decalcification of carbonates followed by clay illuviation. Pedogenic CaCO3 probably resulted from the precipitation of the soil solution near the average depth of wetting front. The pedogenic CaCO3, illuvial clay, mottles, iron manganese features, pedal microstructure and blocky aggregates reveal variation in the pedogenic maturity among and within the loess–paleosol sections. The morphological (both micro- and macro-morphological) attributes of loess–paleosols suggest variation of climatic conditions during the Late Quaternary period in the Karewa Basin of Kashmir Valley, India.

Comment on: Isotopic and micromorphological studies of Late Quaternary loess–paleosol sequences of the Karewa Group: Inferences for palaeoclimate of Kashmir Valley by Dar et al., 2014 (article in press)

Dar and his research team have studied the young sedimentary deposits of the Kashmir Basin (KB) to understand its paleo-geography, paleoecology and paleoclimatic conditions; however, there are some scientific concerns, which if addressed will make this contribution much useful. These are highlighted in this comment. For example, one of the important parts of the study is about the presentation of lithologs through detailed field investigations; however all the studied sections shown in the paper are not backed by field evidence and the data shown is not clearly expressed in some sections. Similarly, authors can produce records on the dominance of specific micromorphological features, which are indicative of a particular pedogenic process. This reveals information specific to climatic and geomorphic conditions besides providing information on tectonic conditions.

Reply to the comment by Shah on “Isotopic and micromorphological studies of Late Quaternary loess-paleosol sequences of the Karewa Group: inferences for palaeoclimate of Kashmir Valley”

Reply to the comment by Shah on “Isotopic and micromorphological studies of Late Quaternary loess-paleosol sequences of the Karewa Group: inferences for palaeoclimate of Kashmir Valley”

Isotopic and micromorphological studies of Late Quaternary loess–paleosol sequences of the Karewa Group: Inferences for palaeoclimate of Kashmir Valley

Pedogenic carbonates, widespread in paleosols throughout the geological ages, have been widely used to infer climatic conditions and vegetation type during their formation. They are ubiquitous and widespread in the Late Quaternary loess–paleosol sequence of the Kashmir Valley, mostly in the form of carbonate nodules. In the present study, pedogenic carbonates are studied to analyze trends in the stable isotopic composition of carbonate nodules across three well-developed loess–paleosol sections in the Kashmir Valley. The stable carbon isotopic (δ13C) analysis reveals a gradual increase of the C4 vegetation towards the top of the sections. The development of C4 plant biomass towards the top of sections possibly reflects water stress and/or reduced atmospheric pCO2 and increasing aridity. The oxygen (δ18O) isotopic analysis reveals little variation with the values ranging from −6.37‰ to −7.75‰, reflecting stable climatic conditions during the development of pedogenic carbonate nodules. The use of geospatial data including digital elevation model (DEM) and Landsat TM remote sensing imagery have added morphological characterization of the topographic and landform features observed in the area. The tectonic uplift of the Pir Panjal Range, variation in the geometry of Karewa Basin and the slope gradient have played a key role in the spatial variation of loess–paleosol sequences in the valley. The Late Quaternary climate changes, deposition of loessic sediments, formation of the interbedded paleosol profiles and the subsequent denudation processes have resulted in the present day typical geomorphic landscape of the Kashmir Valley. The micromorphological analysis of loess–paleosol horizons reveals cold arid to semi-arid climatic conditions prevailed during the Late Quaternary in the valley.

Stable isotope composition of bulk and secondary carbonates from the Quaternary loess-paleosol sequence in Süttő, Hungary

Stable carbon and oxygen isotope composition of pedogenic carbonates were studied from the Quaternary loess-paleosol sequence of Süttő in Hungary to investigate genetic processes in a paleoenvironmental context and to distinguish subtypes. Bulk carbonate samples taken at 2 cm vertical resolution, and microscale secondary (authigenic) carbonates (calcified root cells, carbonate coatings, hypocoatings, and earthworm biospheroids) and concretions at 10 cm resolution were analysed to interpret stable isotope variations. Isotope values of bulk samples were in the range of 2.6‰ to −13.9‰ and −2.3‰ to −17.0‰ (vs. VPDB) for δ13C and δ18O, respectively. The isotope compositions of secondary carbonates clearly distinguished between the organically related and inorganic (direct) precipitation of the different subtypes. In general, secondary carbonates showed more depleted values than bulk samples. Calcified root cells have the most depleted isotope composition with mean values of −16.0‰ and −11.8‰ for δ13C and δ18O, respectively. Results indicate that loess and paleosol secondary carbonates reveal pedogenetic information during the different climatic phases. Carbon and oxygen isotope analyses are valuable to classify secondary carbonates and to serve as proxies for the interpretation of paleoenvironmental conditions, e.g. moisture conditions, leaching, the role of organic matter or vegetation. Secondary carbonates are more reliable than bulk samples because of their direct connection to the host strata.

Stratigraphies and chronologies of late Quaternary loess–paleosol sequences in the core area of the central Asian arid zone

The sporadic distribution of the Quaternary loess in Central Asia makes it hard to establish a regional pedostratigraphy through visual tracing of marker strata. The pedostratigraphic correlation presented here is thus completely based on the radiocarbon chronologies of the four studied sections. The first noticeable feature is that poorly-drained conditions predominated in the period between ∼48,000 and ∼30,000 14C BP, during which three entisols developed at ∼45,000 14C BP, ∼40,000 14C BP, and ∼35,000 14C BP. After a period of loess deposition between ∼30,000 and ∼18,000 14C BP under poorly-drained conditions, an entisol at the westernmost site (Valikhanov, south-central Kazakhstan) developed between ∼18,000 and ∼10,000 14C BP, also under poorly-drained conditions. The time equivalent deposits at Romantic and Zeketai sections to the east do not exhibit any soil-forming characteristics, although poorly-drained conditions are also imprinted in the time-equivalent loess. The Holocene sequences in the Central Asian domain consist of an early Holocene loess unit deposited between ∼10,000 and ∼5,000 14C BP and a late Holocene soil formed during the past ∼5000 years. In comparison, the climate was also wet between ∼48,000 and ∼20,000 14C BP, during which three mollisols developed under well-drained conditions in the Chinese Loess Plateau of the East Asian domain. The loess deposited between ∼23,000 and ∼10,000 14C BP in the Chinese Loess Plateau has neither observable marks of soil formation nor imprints of poorly-drained conditions. The Holocene sequence in the East Asian domain exhibits an out-of-phase relationship with that in the Central Asian domain, consisting of an early Holocene soil formed between ∼9000 and ∼4000 14C BP and a late Holocene loess unit deposited during the past ∼4000 years.

Mid-Late Quaternary loess-paleosol sequence in Lantian’s Yushan, China: An environmental magnetism approach and its paleoclimatic significance

The application of rock magnetism methods to investigating the variations of magnetic minerals in the sediments is an important approach to the reestablishment of paleoclimate evolution. Thus we performed fine magnetic measurements on the loess-paleosol sequence (from L15 upwards to S5, in which L is short for Loess, S is short for Paleosol, the same hereinafter) of Yushan stratigraphic section, which is on the southeastern margin of Chinese Loess Plateau, in Lantian County of China’s Shaanxi Province, and the thickness of which is ca. 40 m. Our study shows that the primary magnetic carriers of loess and paleosol in this section are magnetite, maghemite, hematite and goethite. Thermomagnetic analyses on the samples of representative horizons show that the higher pedogenesis degree of the sediments, the smaller variations of magnetization there will be before and after heating, probably related to the pedogenic alteration of loess sediments. Analyses of several magnetic parameters show a significant discrepancy between the paleoclimatic conditions recorded in the strata from the loess unit L15 upward to the paleosol unit S5 in the study area and those recorded in the relative strata of other sections on the Chinese Loess Plateau, and those recorded in marine sediments, indicating the great impact of regional geological background. Similarly, the rapid and intensive change recorded in the segment from L15 to S9-1, and the significant difference between the paleoclimate evolutions of the two periods before and after the change (from L15 to S9-1, and from L9 to the base of S6) indicate the strong alteration of magnetic carriers in the study area as a result of the alternations of summer and winter monsoons in East Asia.

Correlation of paleoclimatic records between Chinese eolian sediments and Baikal lacustrine sediments

Paleo-records from continental sources such as lacustrine sediments and loess deposits have shown that terrestrial climatic change is closely synchronized with global climate change. The Baikal Drilling Project (BDP) has retrieved cores containing 1 600 m of sediment from the Baikal Lake (BKL) since 1993 (Williams et al., 2001). The unique archive contains a series of paleoclimate and paleoenvironmental proxies resolvable on different time scales over the last 5–12 million years (Kashiwaya et al., 2001a). These long cores provide essential records not only for compari-son with oceanic records of marine processes, but also for the usage as the benchmarks which can help to in-terpret other continental records. Late Cenozoic eolian deposit including Neogene red clay and Quaternary loess-paleosol sequences is widespread in the Chinese loess plateau (CLP), and is regarded as one of the best continental archives of paleoclimate change. The

Characteristics and formation mechanism of pedogenic hematite in Quaternary Chinese loess and paleosols

Abstract Hematite is an important iron oxide mineral in loess–paleosol sequences in northwest China. Samples containing hematite and related minerals in the loess and paleosol units from Chinese Loess Plateau were investigated using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and high resolution transmission microscopy (HRTEM). The results show that there are at least three genetic types of hematite in Quaternary loess–paleosol sequences of northern China: (1) Weathering products of Fe-bearing silicate minerals, such as chlorite and biotite, that precipitated as aggregates of hematite nano-crystals on mineral surfaces; (2) oxidation products of eolian magnetite grains with hematite nano-crystals closely associated with magnetite; (3) coarse (silt-sized) hematite grains present in the fresh loess. Hematite with a nanoporous texture indicates that dehydration of iron hydroxide ferrihydrite is the main mechanism for the formation of hematite coating during chemical weathering of Fe-bearing silicates. It is proposed that nano-phase hematite is primarily responsible for the red color of the paleosol units. Paleosol layers are also characterized by higher magnetic susceptibility and increased oxidation of eolian magnetite. It is proposed that the major contribution to magnetic susceptibility is from the nano-phase magnetite that may be related to microbial activity. This research demonstrates that the study of mineral characteristics, formation mechanisms and the relationship between hematite, other iron oxides, and Fe-bearing silicate minerals helps to understand better the geochemical process in loess, both before and after dust deposition. In addition our study helps to explain the correlation between magnetic susceptibility and paleoclimate in northern China during the Quaternary.

Influence of the aging of Fe oxides on the decline of magnetic susceptibility of the Tertiary red clay in the Chinese Loess Plateau

Magnetic properties, free and active Fe oxides, grain size distribution and mineral assemblage of a Quaternary loess–Tertiary red clay (TRC) section in Lingtai County in the Chinese Loess Plateau were studied. The results suggest that the TRC of the Lingtai section shares similar aeolian characteristics with the overlying Quaternary loess-paleosol sequence (QLPS), but the former is generally more intensively weathered than the latter, as indicated by its higher citrate–bicarbonate–dithionite (CBD) extractable Fe (Fe d), finer grain size and lower content of easily weathered primary minerals. However, magnetic susceptibility ( χ lf) and magnetic remanence ( χ arm, SIRM and SOFT etc.) of the main part of the TRC are significantly lower, implying the decline of ferrimagnetic minerals (FM). In contrast, hematite and goethite in the TRC is significantly enhanced, as indicated by its higher HIRM. The acid ammonium oxalate (AAO) extractable Fe (Fe o) of the whole section sharply decreases with increasing age. Fe o and Fe o/Fe d values of the section are significantly correlated with χ lf. Especially in the TRC, the low values of Fe o and Fe o/Fe d correspond to weak χ lf. This suggests a significant influence of the age-related transformation of Fe oxides on the decline of FM in the TRC. Lower FM and higher hematite and/or goethite in the TRC further suggest the transformation of FM into hematite with the aging of Fe oxides during post-depositional processes, though more evidence is needed to understand the processes involved. χ lf of the TRC in the Chinese Loess Plateau mostly cannot be regarded as a promising paleoclimatic proxy because its weak magnetism does not correlate to its strong pedogenesis.

Magnetic susceptibility of the Xifeng section and its paleoclimate significance

Magnetic susceptibility (MS) is one of the most important indicators of the East- Asia summer monsoon. Presented in this study is a high resolution magnetic susceptibility record from the Xifeng section, which consists of Quaternary loess-paleosol sequence and Pliocene red clay. Variations in magnetic susceptibility are well correlated with the δ18O record in deep-sea sediments and the eolian flux of Greenland. The climatic evolution in the Xifeng section shows that since the Late Tertiary, the driving force of the East-Asia paleo-monsoon is correlated with solar radiation on a 10-ka time scale.