Chinese Loess-paleosol Sequences Research Articles

Morphological characters and multi-element isotopic signatures of carbonates from Chinese loess–paleosol sequences

Morphological characters and multi-element isotopic compositions of carbonates from the loess–paleosol sequences in Northwestern China are examined to explore the origin of the minerals. Samples are collected from various sections ranging from Holocene to 0.9 Ma within the sequences and fractions with grain sizes >45 and <2 μm are separated from the bulk soil and examined by SEM and TEM. The results show that the grains >45 μm exhibit an almost perfect spherical shape while those <2 μm are dominated by nano-rods having diameters of 30–50 nm and lengths of 0.3–2 μm, presumably indicating the detrital origin of the coarse fractions and the authigenic characters of the fine ones. Such implications are corroborated by the multi-elemental isotopic compositions of the carbonate minerals. A comparison of the δ 13C and δ 18O values between minerals and biologically originated samples indicates that the <2 μm fractions have a similar composition to those of coexisting land snail shells. Additional differences between the two size fractions also manifest in the ratios of 206Pb/ 204Pb, 207Pb/ 204Pb, 208Pb/ 204Pb, and 87Sr/ 86Sr. These results suggest the utility of fine carbonate particles in the soil profile in reconstructing a potentially higher resolution δ 13C and δ 18O time series to elucidate the paleoclimatic fluctuation in the Chinese Loess Plateau during Pleistocene. The discovery of the nano-rod calcite in Chinese loess, together with previous findings of the similar mineral form in Asian dust, strongly suggests the possibility that these highly reactive CaCO 3 form may alter the aerosol properties during transport.

Climatic conditions recorded by terrestrial mollusc assemblages in the Chinese Loess Plateau during marine Oxygen Isotope Stages 12–10

Past analogs for our present interglacial have been sought for better understanding of our present and future climate. Marine Isotope Stage 11 (MIS 11) has long been considered to be a good candidate and has gained increasing attention in recent studies of marine and terrestrial records. In the Chinese loess–paleosol sequences, S4 soil, interpreted as equivalent to MIS 11, yields a very precise terrestrial paleoclimate record of environmental changes that prevailed during this period. In this study, two high-resolution terrestrial mollusc records from the Loess Plateau have been analyzed to characterize climate variability during the periods of MIS 12–10. The changes in environment and climate, indicated by the variations in abundance of land mollusc species, are thus documented. Our mollusc results show that the L5 loess, equivalent of MIS 12, developed under relatively cold and dry conditions. Climate during this period was not as severe as indicated in the marine isotopic records. An episode of warmer and more humid condition occurred at the middle stage of the MIS 12, reflecting a summer monsoon strengthened during the glacial interval. A similar scenario has been observed in the middle part of MIS 10. In addition, our mollusc records provide insight into the climate conditions over the Loess Plateau during MIS 11, a general warm–humid climate dominated during the formation of S4 soil. But at least four fluctuations occurred at Xifeng region, reflecting unstable climate conditions and regional climate differences within the Loess Plateau during this period. Our study shows that the early part of S4, spanning over 30 ka, was very warm and humid, while the late part was characterized by mild-cool conditions. Comparison of mollusc species compositions of both MIS 11 and Holocene intervals reveals different climate conditions. The early part of MIS 11 was warmer and more humid than the Holocene optimum period, while the late part of MIS 11 was similar or cooler. Our study indicates that the extent of warming during the Holocene in the Loess Plateau might be significantly less than the conditions that prevailed during the MIS 11 interglacial period.

Loess–paleosol stratigraphy of Dukso area, Namyangju City, Korea (South)

As Korea lies between China, with a drier climate, and the wetter Japanese Islands, the Korean loess–paleosol stratigraphy constitutes an important record of variations in the East Asian monsoon climate. The loess–paleosol sequence consists of three loess layers (L1LL1, L1LL2, and L2) and three paleosols (L1SS1, S1, and S2) in the study area. L1LL1 accumulated near the surface, and is only about 5 cm in outcrop because it was removed for farming. L1SS1 is about 103 cm thick. Soil crack structures developed in the upper part of L1SS1 were formed by shrinkage or as seasonally frozen ground soil wedges during the early cold-dry stage of glacial period. L2 is 48 cm thick, with OSL ages of 167,000 and 186,000 yr. Magnetic susceptibilities of paleosols were higher than the loess layers. Fine quartz grains in the loess layers are characterized by rounded shape and pitted surfaces. Based on the presence of the AT tephra, OSL ages, soil color, soil crack structure, magnetic susceptibility, and median diameter, the loess–paleosol sequence of the Dukso section can be correlated with the Chinese loess–paleosol sequence between MIS 2 and 7.

Oxygen-isotope record of paleorainwater in authigenic carbonates of Chinese loess-paleosol sequences and its paleoclimatic significance

Oxygen isotopic compositions of rhizoconcretions and land snail shells were measured to reconstruct the δ 18O profiles of paleorainwater ( δ 18O p) for well-dated loess-paleosols in Luochuan, China. To assess the paleoclimatic significance of δ 18O p, factors that control the spatial and temporal δ 18O variations of rainwater in East Asian monsoon regions were investigated. Modern records indicate that the spatial δ 18O variations of modern rainwater ( δ 18O m) are closely related to near surface temperature ( T) and the amount of precipitation ( P). In order to separate the effects of T and P on the δ 18O m, a linear relationship between δ 18O m, T and the natural logarithm of P is established by multiple regressing analyses: δ 18 O m = 1.070 + 0.326 × T − 2.041 × ln ⁡ P The δ 18O of paleorainwater over the past 130 Ka in Luochuan area is calculated by the modern-spatial δ 18O– T– P relationship using estimated T and P from other paleoclimate records. The calculated δ 18O match well to those reconstructed from the authigenic carbonates, which implies that the spatial and temporal δ 18O variations of rainwater in East Asian monsoon regions have similar δ 18O– T– P relationships and the authigenic carbonates in Chinese loess-paleosol sequences can serve as valid records of δ 18O p. As an application of the δ 18O– T– P relationship, P variation in the past 130 ka in Luochuan was evaluated. The reconstructed P is in good agreement with other studies using different approaches. Our results suggest higher precipitation in Marine Isotope Stages 1, 3 and 5, reflecting intense summer monsoon influences during these periods of time.

Weathering history indicated by the luminescence emissions in Chinese loess and paleosol

In the past several decades, luminescence emissions from quartz and feldspar grains have been used mainly for optical dating of detrital sediments. Here we extend the luminescence application field, with variations in luminescence emissions being introduced to reflect weathering degree and recover its potential paleoclimate information in the Chinese loess–paleosol sequence. Four wavebands (320–340, 405–425, 465–495 and 545–575 nm) of infrared stimulated luminescence (IRSL) from polymineral grains (4–11 μm) are presented, and IRSL intensities show distinct variation between the well-developed paleosol, weakly developed soil and typical loess in the last glacial-interglacial cycle. Based on the facts that IRSL signal originates from feldspars and optically stimulated luminescence (OSL) after long duration of Infrared stimulation from quartz grains, referred to as [post-IR] OSL signal, the IRSL/[post-IR] OSL ratios were proposed to represent the relative abundance of feldspar and quartz. This ratio was linked to the degree of weathering in Chinese loess and paleosol units. In addition, the ratios between the four IRSL emissions may also show the relative abundances of four corresponding feldspar groups. Compared to the magnetic susceptibility record, the IRSL/[post-IR] OSL ratios are more sensitive to the degree of weathering in Chinese loess. Convenient to measure and available as a byproduct of routine optical dating, such ratios may act as potential proxies of paleoclimate in Chinese loess.

Effect of Magnetotactic bacteria on the susceptibility in Chinese loess–paleosol sequences

A simulated experiment of Magnetotactic bacteria (MB) effect on susceptibility in the samples from the 5th to 6th loess layers (L 5–S 5–L 6) in Xifeng and Duangjiapo sections was performed. It is demonstrated that MB can increase the susceptibility of the samples and promote newly produced magnetic minerals from paleosol layers under the suitable condition. The tiny magnetic particles and arranged as a chain in the minerals less than 30 μm were found in the paleosol sample of Duangjiapo section.

Periodicities of palaeoclimatic variations recorded by loess-paleosol sequences in China

Palaeoclimatic periodicity recorded by Chinese loess-paleosol sequence has been investigated for a number of years. However, conclusions from previous investigations are still controversial, and interpretation of cycle evolution is quite equivocal. In this study, two typical loess-paleosol sequences (148 and 191m in thickness, respectively) in the central Chinese Loess Plateau are sampled (3872 samples total) and measured for grain size distribution and magnetic susceptibility in order to reconstruct the palaeoclimatic changes over the past three million years. On the basis of a new, sensitive proxy indicator of palaeoclimate and a newly developed independent time scale (not orbitally-tuned), two time series of Asian dust storm variations, which are highly related to the palaeoclimate system changes, are obtained. Wavelet and spectrum analyses indicate that there are approximately 400, 200, 100, 66, 57, 41, 31, 27 and 22kyr cycles in these typical loess-paleosol records. Some orbital-driven cycles are weak and are not well presented in the new time series while some non-orbital cycles are found. Since the eccentricity frequencies of the solar irradiance of approximately 400 and 100kyr are preserved in these palaeoclimatic sequences, the lack of relatively short-time orbital cycles of 41-kyr-obliquity and 22-kyr-precession cycles in part of the two time series may be explained by the relatively low time-resolution of the loess-paleosol deposits. Through an astronomical estimate, the obliquity and precession cycles should leave stronger footprints on records of palaeoclimatic variations at the middle latitudes of the northern hemisphere. The presence of non-orbital cycles may be explained by unstable dust deposition processes and pedogenic processes in the paleosol units, which could misrepresent or obliterate the imprint of the solar irradiance frequency. This conclusion may indicate that one should be cautious when investigating specific palaeoclimatic changes (e.g., at sub-orbital time scales) recorded in loess deposits, especially in the paleosol units.

Characterization of the Chinese loess–paleosol stratigraphy by whiteness measurement

Changing color is one of the most striking features of loess–paleosol sequences in central China: the loess is light yellow and the interstratified paleosols are reddish-brown. Until a few years ago, conventional color description of loess sediments was made using a qualitative visual method, the Munsell system. To better understand the character of the color changes and to quantify results, whiteness and magnetic susceptibility were compared from four loess–paleosol sequences. Results show that the two parameters are highly correlated in the four sequences studied. Grain-size analysis and chemical extraction experiments indicate that the concentration and species of fine-grained iron oxides are major factors determining color changes in loess and paleosols. Whiteness and latitude values from the last glacial–interglacial sequence exhibit a linear relationship suggesting that whiteness will be a useful tool for reconstructing past atmospheric circulation, especially the East Asian summer monsoon. Whiteness and magnetic susceptibility in the Luochuan profile over the past 0.9 Myr display a strong correlation indicating that whiteness can be also used to reveal a long climatic history from Chinese loess–paleosol sequences.

Rapid and Quantitative Measurement of Hematite and Goethite in the Chinese Loess-Paleosol Sequence by Diffuse Reflectance Spectroscopy

AbstractThe long, continuous deposition of dust in the Chinese loess plateau offers a unique opportunity to study the nature of Fe oxide formation in a wide range of climatic conditions. A technique to obtain quantitative estimates of the concentration of hematite and goethite in loess and paleosol samples is reported. Experiments using diffuse reflectance spectroscopy on sets of laboratory mixed and natural loess and paleosol samples show that it is possible to obtain rapid and quantitative estimates of the absolute concentration of hematite and goethite in the Chinese loess sediments. Typical loess and paleosol samples were deferrated using the CBD procedure to produce a natural matrix material to which hematite and goethite in known weight percentages were added to produce a set of calibration standards. Spectral violet, blue, green, yellow, orange, red and brightness of standards were calculated from the reflectance data and served as independent variables for a multiple linear regression analysis. The effect of changing matrix from loess to paleosol was overcome by including a variety of different loess and paleosol samples in the regression equations. The resulting calibration equations provide estimates of wt.% hematite and goethite and have correlation coefficients &gt;0.93. The total measured hematite and goethite concentrations exhibited consistent variations with CBD extractable iron. Tests of the equations for buffering changes in matrix composition were run with samples of varying mineralogical composition (calcite, illite, etc.) and demonstrated that the equations are well buffered for changes in matrix composition from loess to paleosol.

Multiple origins and interpretations of the magnetic susceptibility signal in Chinese wind-blown sediments

In most Chinese loess–paleosol sequences, high magnetic susceptibility values are found in the soil horizons, with low values in the loess layers. The susceptibility signal has been widely used as a proxy climatic indicator. However, both the causes and mechanisms which control susceptibility still remain controversial. Our recent studies challenge some earlier interpretations of the magnetic susceptibility signal in Chinese wind-blown sediments. First, the prevailing hypothesis of pedogenic origin cannot totally account for the susceptibility variations in many sections. Second, in some cases, the principal carrier of the magnetization seems not to be the ultrafine pedogenic minerals, rather coarse lithogenic magnetic minerals derived from local sources can also contribute significantly to the susceptibility signal. Finally, not all the Chinese soils have higher susceptibility values than that of loess or sand layers, opposite relationships do exist. It is concluded that the source and causes of susceptibility may be different from site to site or even at different times at a given site. Any single hypothesis cannot completely account for the susceptibility variations in the Chinese Loess Plateau and its surrounding regions. Besides the previous explanations of carbonate leaching, pedogenic processes and organic decomposition, the contribution of source materials to magnetic susceptibility must also be taken into account.

Paleo-environmental study on the growth of magnetotactic bacteria and precipitation of magnetosomes in Chinese loess-paleosol sequences

405 samples were collected from L5-S5-L6 in consideration of obvious variations in susceptibility of the geological sections, which are section Xifeng in Gansu Province and section Duanjiapo in Shaanxi Province for study of magnetotactic bacteria (MB) and magnetosomes (MS) in Chinese loess-paleosol sequences. MB in each sample were observed by TEM after being cultured under 8–18°C., room temperature (RT), 25°C., 26°C and 30°C conditions. In general, MB are distributed widely in loess-paleosol sequences, fewer in loess layers with predomination of vibriod in shape. However, there are more MB in paleosol layers with morphological varieties such as roddish, vibriod and occasionally approximately coccus. The magnetosomes (MS) in MB of paleosol are usually arranged in chains along the cells. It was also found that MB growth and MS formation are associated with the environment in which MB live. It can be inferred from the distributions of MB and MS that the paleoclimates fluctuated during the formation of loess-paleosol sequences in the Chinese Loess Plateau. The climate became gradually warmer but displayed more frequent fluctuations from the northwest to the southeast of the Plateau.

EPR studies of Mn2+ in the Loess Plateau of central China: Implication for variation of the East Asia summer monsoon

Mn2+ EPR intensity recorded in the Chinese loess-paleosol sequence shows close correlation with magnetic susceptibility and Sr content as well as the oscillation of paleoclimate. Thus Mn2+ EPR signal can serve as an indicator sensitive to the East Asia summer monsoon intensity fluctuations.

Variable shape of magnetic hysteresis loops in the Chinese loess-paleosol sequence

Shape of magnetic hysteresis loops of the Chinese loess-paleosol sequence is variable with low-field susceptibility and is weakly constricted in samples with intermediate susceptibility (~1.0 × 10−6 m3/kg). The analyses of the hysteresis loops show that both low- (ferrimagnetic) and high-coercivity (antiferromagnetic) components are present and the ferrimagnetic component dominate the magnetic characteristics. The ratio of ferrimagnetic over antiferromagnetic minerals (S ratio) and the superparamagnetic fraction increase with increasing susceptibility. Neither simple two-component mixtures of ferrimagnetic and antiferromagnetic minerals nor of single-domain and superparamagnetic grains fully explain the constricted hysteresis loops. We interpret the variation of the loop shape with susceptibility in the following way. When the ratio of the ferrimagnetic to antiferromagnetic contribution is relatively low (low susceptibility), the broad loop is controlled by lithogenic ferrimagnetic and antiferromagnetic minerals. For samples with intermediate susceptibility values, constricted shape originates from an addition of a broad loop from the lithogenic fraction and a narrow loop from a pedogenic fraction with high superparamagnetic content. Then with further susceptibility increase, the constricted shape almost disappears and the loop is dominated by the pedogenic fraction. The variation of hysteresis loop shape with susceptibility can be a useful indicator of the degree of pedogenesis for loess-paleosol samples.

地球環境変化とヒマラヤ・チベット山塊の役割 中国内陸部のレス・古土壌堆積物と日本海堆物の粘土鉱物からみた東アジアにおける過去２４０万年間のモンスーン・偏西風変動

Activities of Asian monsoon and westerlies during the last 2.4Ma were determined through the investigation of sedimentary features in the Chinese loess-paleosol sequences and the deep-sea sediments of the Sea of Japan. It was already known that sequential changes of magnetic susceptibility in the loess-paleosol sequences of the Chinese Loess Plateau were closely concerned with the glacial-interglacial cycles. Also, sequential changes of illite crystallinity, expressing as full width of half maximum of 10 A peaks by X-ray diffraction patterns in late Quaternary fine-grained sediments at Site 795A of Ocean Drilling Program in northeastern part of the Sea of Japan, were well correlated to standard records of oxygen isotope changes by SPECMAP. The samples of this research were derived from the Luochuan of northwestern China and from deep-sea sediments in ODP site 795A. This research is dealing with the changes of magnetic susceptibility and/or clay mineralogy of the loess-paleosol sequences during the last 2.4 Ma.The results are summarized as follows:1) Illite is one of the main detrital minerals in the loess-paleosol sequences, and illite concentrations in loess are higher than those concentrations found in paleosol. Therefore, illite crystallinity and concentrations are useful indicators to detect concentrations of eolian dust deriving from the Chinese Loess Plateau.2) During interglacial periods, wet atmospheres drifted from the Eastern China Sea into the inland area of the Asian Continent. This increase of moisture has promoted the hydration and decomposition of illite crystals in paleosols.3) According to the investigation of sedimentary features, it is obvious that there was little supply of eolian dust origin minerals transported from the arid area of western China to the Chinese Loess Plateau. This fact cannot always support the formation process of the loess-paleosol sequences, as it was interpreted by Kukla et al.(1988).4) The large amplitudes of Magnetic susceptibility in the loess-paleosol sequences during the last 0.6 Ma and there was a high degree of illite crystallinity in the deep-sea sediments during the last 0.8 Ma appeared. These facts suggest that changes of atmospheric circulations were caused by the uplift of the Himalayan/Tibetan Plateau about 0.6-0.8 Ma ago.

The role of maghemite in the enhancement of magnetic signal in the Chinese loess-paleosol sequence: An extensive rock magnetic study combined with citrate-bicarbonate-dithionite treatment

We have conducted a rock magnetic study of selected Chinese loess samples before and after citrate-bicarbonate-dithionite (CBD) treatment. Our study is more extensive than previous ones and reveals new details of the magnetic carriers which are related to paleoclimate change. Three pairs of paleosol S1 (the top paleosol layer in the Lishi Formation) and loess L2 (underlying S1) from three localities (Xining, Xifeng, and Jixian) were investigated by using a variety of magnetic methods. After the paleosols were treated with CBD, which removes all maghemite grains and the finest grains of magnetite, magnetic susceptibility decreased from 77 × 10 −8 to 20 × 10 −8 m 3/kg in Xining, from 165 × 10 −8 to 30 × 10 −8 m 3/kg in Xifeng, and from 180 × 10 −8 to 25 × 10 −8 m 3/kg in Jixian, anhysteretic remanent magnetizations (ARM) were reduced to less than one tenth of the original values in the three sites, and saturation magnetization ( J s) decreased by about 60% in Xining and 70% in Xifeng and Jixian. These reduced values in the paleosols after CBD treatment are similar to those of the corresponding underlying loess samples, which, however, did not show significant decrease after CBD treatment. Room-temperature frequency dependence of susceptibility, high-temperature dependence of susceptibility, and low-temperature SIRM demagnetization of the paleosol and loess samples before and after CBD treatment confirm that in addition to superparamagnetic (SP) particles (magnetite and/or maghemite), the CBD removable magnetic carriers also include maghemite of grain sizes larger than SP.

Grain Size of Quartz as an Indicator of Winter Monsoon Strength on the Loess Plateau of Central China during the Last 130,000 Yr

The Chinese loess-paleosol sequence constitutes an important record of variations in Asian monsoon climate over the past 2.4 myr. Magnetic susceptibility of loess and paleosols has been used as a proxy for summer monsoon intensity, while median grain size has been regarded as a measure of the strength of winter monsoon winds that were responsible for most of the dust transport. However, median grain size is only an approximate index of winter monsoon strength because both paleosols and loess have been modified, to various degrees, by weathering processes that have produced pedogenic clay. The quartz component of loess and paleosols is largely unaffected by weathering processes and therefore constitutes a more reliable proxy index of monsoon wind strength. Median grain size (Qmd) and maximum grain size (Qmax) values of monomineralic quartz isolated from the loess-paleosol section at Luochuan in the central Loess Plateau are characterized by two main intervals during the last ca. 130,000 yr when these parameters were significantly greater than 9 and 85 μm, respectively, and three main intervals when they were lower. The data imply that the winter monsoon weakened during the intervals with low Qmd and Qmax values, which coincide with marine oxygen isotope stages 5, 3, and 1, and was strongest ca. 67,000 and 20,000 yr ago during isotope stages 4 and 2. However, both quartz grainsize records display second-order high-frequency, high-amplitude variations, which are lacking in the magnetic susceptibility record, that imply rapid and significant changes in atmospheric conditions that affect dust transport and deposition.

Pedogenesis and paleoclimate: Interpretation of the magnetic susceptibility record of Chinese loess-paleosol sequences: Comments and Reply

Research Article| September 01, 1994 Pedogenesis and paleoclimate: Interpretation of the magnetic susceptibility record of Chinese loess-paleosol sequences: Comments and Reply B. A. Maher; B. A. Maher 1School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom Search for other works by this author on: GSW Google Scholar R. Thompson; R. Thompson 2Department of Geology and Geophysics, University of Edinburgh, Edinburgh EH8 9YL, United Kingdom Search for other works by this author on: GSW Google Scholar Xiuming Liu; Xiuming Liu 3Department of Geography, University of Liverpool, Liverpool L69 3BX, United Kingdom Search for other works by this author on: GSW Google Scholar Jan Bloemendal; Jan Bloemendal 3Department of Geography, University of Liverpool, Liverpool L69 3BX, United Kingdom Search for other works by this author on: GSW Google Scholar Tim Rolph; Tim Rolph 4Geomagnetism Laboratory, University of Liverpool, Liverpool L69 3BX, United Kingdom Search for other works by this author on: GSW Google Scholar Kenneth L. Verosub; Kenneth L. Verosub 5Department of Geology, University of California, Davis, California 95616 Search for other works by this author on: GSW Google Scholar Pinchas Fine; Pinchas Fine 6Institute of Soils and Water, Volcani Center, Bet Dagan 50-250, Israel Search for other works by this author on: GSW Google Scholar Michael J. Singer; Michael J. Singer 7Department of Land, Air and Water Resources, University of California, Davis, California 95616 Search for other works by this author on: GSW Google Scholar Jeff TenPas Jeff TenPas 7Department of Land, Air and Water Resources, University of California, Davis, California 95616 Search for other works by this author on: GSW Google Scholar Geology (1994) 22 (9): 857–860. https://doi.org/10.1130/0091-7613(1994)022<0857:PAPIOT>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation B. A. Maher, R. Thompson, Xiuming Liu, Jan Bloemendal, Tim Rolph, Kenneth L. Verosub, Pinchas Fine, Michael J. Singer, Jeff TenPas; Pedogenesis and paleoclimate: Interpretation of the magnetic susceptibility record of Chinese loess-paleosol sequences: Comments and Reply. Geology 1994;; 22 (9): 857–860. doi: https://doi.org/10.1130/0091-7613(1994)022<0857:PAPIOT>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract No abstract available This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Pedogenesis and paleoclimate: Interpretation of the magnetic susceptibility record of Chinese loess-paleosol sequences

Research Article| November 01, 1993 Pedogenesis and paleoclimate: Interpretation of the magnetic susceptibility record of Chinese loess-paleosol sequences Kenneth L. Verosub; Kenneth L. Verosub 1Department of Geology, University of California, Davis, California 95616 Search for other works by this author on: GSW Google Scholar Pinchas Fine; Pinchas Fine 2Institute of Soils and Water, Volcani Center, Bet Dagan 50-250, Israel Search for other works by this author on: GSW Google Scholar Michael J. Singer; Michael J. Singer 3Department of Land, Air and Water Resources, University of California, Davis, California 95616 Search for other works by this author on: GSW Google Scholar Jeff TenPas Jeff TenPas 3Department of Land, Air and Water Resources, University of California, Davis, California 95616 Search for other works by this author on: GSW Google Scholar Geology (1993) 21 (11): 1011–1014. https://doi.org/10.1130/0091-7613(1993)021<1011:PAPIOT>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Kenneth L. Verosub, Pinchas Fine, Michael J. Singer, Jeff TenPas; Pedogenesis and paleoclimate: Interpretation of the magnetic susceptibility record of Chinese loess-paleosol sequences. Geology 1993;; 21 (11): 1011–1014. doi: https://doi.org/10.1130/0091-7613(1993)021<1011:PAPIOT>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract In the Chinese loess-paleosol sequences from Luochuan, Haanxi province, China, variations in the magnetic susceptibility have been accepted as an excellent proxy for paleoclimate, and the standard interpretation is that climatic processes have enhanced the magnetic susceptibility of the paleosols beyond the base-line level of the loess. By using mineral magnetic properties and a soil-chemistry extraction procedure, we show that most of the magnetic susceptibility signal in both the paleosols and the loess is due to pedogenesis. In effect, loess deposition and pedogenesis are competing processes at all times, and the presence of a paleosol simply indicates that the latter process was predominant. These results imply that any interpretation of the paleoclimate record of loess-paleosol sequences must recognize the pedogenic nature of the magnetic susceptibility signal and that the focus of future research must be on the critical role of climate in the development of the paleosols. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Magnetic susceptibility evidence of monsoon variation on the Loess Plateau of central China during the last 130,000 years

The magnetic susceptibility of loess and paleosols in central China represents a proxy climate index closely related to past changes of precipitation and vegetation, and thus to summer monsoon intensity. Time series of magnetic susceptibility constructed for three loess-paleosol sequences in the southern part of the Chinese Loess Plateau document the history of summer monsoon variation during the last 130,000 yr. They correlate closely with the oxygen isotope record of stages 1 to 5 in deep-sea sediments. Soils were forming during intervals of strong summer monsoon, whereas loess units were deposited at times of reduced monsoon intensity. The Chinese loess-paleosol sequence can thus be viewed as a proxy record of Asian monsoon variability extending over the last 2.5 myr.