https://orcid.org/0000-0002-2112-0082
Figures
Abstract
The upper Hanjiang River basin has been an important area for human life and production since ancient times. Marine Isotope Stage 3 (MIS 3) is a special period of relatively warm and humid climate during the last glacial period. However, the climate record of MIS 3 in this region, especially the difference of chemical weathering characteristics between this region and the northern Loess Plateau, remains unclear. An in-depth field investigation was conducted in this study on the upper Hanjiang River valley and we found a typical loess-paleosol profile named Tuojiawan (TJW). Multi-proxy indicators including sedimentology, chronology, magnetic susceptibility, grain size, and geochemistry were used to analyze the climate change characteristics. The results show that the stratigraphic consists of fluvial deposits (T1-al1), interaction layer (T1-al2), Malan loess (L1-3), paleosol (L1-S2), Malan loess (L1-2), paleosol (L1-S1), Malan loess (L1-1), transitional loess (Lt), paleosol (S0), recent loess (L0), and modern soil (MS). The pedogenic intensity varies significantly in different layers and presents a tendency of S0 > L1-S2 > L1-S1 > Lt > L1 (L1-1, L1-2, L1-3). This indicates that MIS 3 is not a continuously dry and cold stage. TJW profile also showed a phase of gradual shift to warm-wet (11.5–8.5 ka BP), maximum warm-wet period (8.5–3.1 ka BP), and a phase of gradual shift to cool-dry (after 3.1 ka BP). Compared with the records of the Loess Plateau, the chemical weathering intensity of the warm and humid event in the upper reaches of the Hanjiang River in the late MIS 3 is different, which reveals the unique response mode of the region to global climate change and may be controlled by different monsoon subsystems.
Citation: Zhang W, Lv L, Lu J, Lv Y, Wang H, Xu X, et al. (2026) Multi-index analysis of climate change events recorded by loess-paleosol deposits in the upper Hanjiang River valley since MIS 3. PLoS One 21(3): e0341061. https://doi.org/10.1371/journal.pone.0341061
Editor: Yougui Song, Institute of Earth and Environment, Chinese Academy of Sciences, CHINA
Received: April 27, 2025; Accepted: December 30, 2025; Published: March 4, 2026
Copyright: © 2026 Zhang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the manuscript and its Supporting Information files.
Funding: LJY, ZWT acknowledge funding support from the Yancheng Science and Technology Bureau to Yancheng Natural Science Foundation (grant number YCBK2024006).
Competing interests: The authors have declared that no competing interests exist.
1. Introduction
Loess-paleosol sequence is considered to be one of the best terrestrial archives for recording paleo-environmental evolution [1]. Many Loess Plateau profiles recorded a relatively warm-wet climate stage in the last glacial period [1–6], which was significantly in contrast to the dry-cold climate, and the temperature and humidity degree was lower than that of the Holocene and the last interglacial period [3,7], occurrence time of which may correspond to MIS 3 period [7,8]. This relatively warm-wet climate change event has also been recorded in loess profiles in the middle and lower reaches of the Yangtze River [9]. Although climate during MIS 3 was relatively warm and wet, as recorded in many loess profiles, the changing characteristics recorded by various profiles were still quite different [3,7,8], as different classification standards for climate change may lead to different divisions of cool and warm stages, while the late and early temperature and humidity in MIS 3 are consistent. Further theoretical verification of these issues is needed.
Located at the southern foot of the Qinling Mountains in China, the Hanjiang River lies within the transition zone between the temperate and subtropical monsoon climates, making it highly sensitive to climate change. In recent years, the spatial distribution, stratigraphy, chronology and characteristics of pedogenesis of the Hanjiang River valley loess have been studied deeply [5,6,10–12]. However, the climate change record during MIS 3 in this area has not been studied yet. It is also important to examine whether these climate changes are regional or global. In this study, we focused on Tuojiawan (TJW) loess-paleosol profile in the upper Hanjiang River valley. Through a comprehensive study of its magnetic susceptibility, grain size, geochemical elements, with optical stimulated luminescence (OSL) age, and aimed at: (1) using alternative climate indicators to study the process of climate change in the upper reaches of the Hanjiang River since MIS 3; (2) comparing with climate records from different regions, and obtaining the regional climate change records since the end of the Late Pleistocene period.
2. Geographical setting
The Hanjiang River, a major tributary of the Yangtze River in China, flows through Shaanxi and Hubei provinces in central China (Fig 1A). The Hanjiang River has a length of 1577 km and a catchment area of 1.59 × 105 km2. The mean annual runoff is 5.17 × 1010 m3 and the mean suspended sediment load is 2.5 kg/m3. The upper reach of the mainstream (Danjiangkou Reservoir upstream) is 925 km long with a drainage area of 9.53 × 104 km2 and an average annual runoff of 3.79 × 1010 m3 [13]. In addition, the upper Hanjiang River plays an important role in furnishing the main water source for the Middle Route Project of the South-North Water Transfer Project of China [14].
(A) The location of the upper Hanjiang River drainage basin between the Yunxi and Yunxian Reaches (the area enclosed in red lines). (B) The location of the TJW profile and other comparison profile sites (after https://www.gscloud.cn) [5,6] within the Yunxian Basin in the reaches of the Hanjiang River valley. (C) Monthly average temperature and precipitation in Yunxi County from 1981 to 2010 (after https://www.nmc.cn). (D) Photo of TJW profile.
The upper Hanjiang River flows from west to east between the Qinling and Dabashan Mountains and cuts into granitic and metamorphic rocks, forming deep and narrow bedrock gorges with some large and small basins along the mainstream of the Hangjiang River [15]. Three visible alluvial terraces, which are 10–15 m, 30–40 m, 60–70 m above present river water level respectively, have been identified in the basins of the upper Hanjiang River [10,16]. In exposed riverbank cliffs, eolian loess-paleosol sequences were often found overlying past fluvial deposits such as floodplain sediments and gravels [5,13].
The upper Hanjiang River is located in the humid region with a subtropical monsoonal environment that is extremely sensitive to climate change. Mean annual temperature ranges from 14–16 °C and mean annual precipitation from 800–900 mm, which is affected by the warm and humid air currents of East Asian summer monsoon and Indian summer monsoon (Fig 1A). Over 75% of precipitation occurs during May and October due to the special hydro-climate conditions of high seasonal variability.
3. Materials and methods
3.1. Materials
Extensive field investigations were carried out on the first terrace in the Yunxian Basin from 2010 to 2014. Detailed geomorphological, pedological, sedimentological and stratigraphic observations were performed throughout the Yunxian Basin. A complete loess-paleosol sequence that had not been disturbed by human activities or soil erosion processes was discovered at the village of TJW in the town of Guanyin, Yunxian county, Hubei Province, China (TJW profile, 32°05’47“N, 110°22’51”E, 168 m asl, Fig 1B). The pedostratigraphy of the TJW profile from bottom to top is listed as fluvial deposits (T1-al1) →Interaction layer (T1-al2) → Malan Loess (L1-3) →Paleosol (L1-S2) →Malan Loess (L1-2) →Paleosol (L1-S1) →Malan Loess (L1-1) →Transitional loess (Lt) →Paleosol (S0) →Recent loess (L0) →Modern soil (MS). The detailed stratigraphic description at the TJW profile is shown in Table 1. The stratigraphic characteristics of TJW profile are basically the same as those of other loess profiles in the Hanjiang River basin, such as Guixianhekou (GXHK) profile, Mituosi (MTS) profile and Qianfangcun (QFC) profile in Yunxian County [5-6,12], as shown in Fig 2. The TJW profile provides a well-preserved record of regional climate evolution since 55 ka BP.
3.2. Methods
After pedo-stratigraphic subdivisions, 353 sediment samples were collected at 2 cm intervals from 0 to 570 cm and at 4 cm intervals from 570 to 838 cm in the TJW profile. All the experiments were carried out in the Environment Change Laboratory of Shaanxi Normal University. Magnetic susceptibility was measured using 10 g of sample with a Bartington MS2 magnetic susceptibility meter (0.47/4.7 kHz). The grain size distribution of the samples were analyzed using a Beckman Coulter laser diffraction particle size analyzer with dispersant (Calgon) after digestion with 10% H2O2 and 10% HCl to remove organic matter and carbonates, respectively [17]. Geochemical element analysis was performed using a PANalytical PW2404 X-ray fluorescence spectrometer.
Samples for optically stimulated luminescence (OSL) dating were taken with a steel cylinder from the profile and immediately packed with aluminum foil during the fieldwork. The OSL measurements were performed in the OSL laboratory at Shaanxi Normal University. OSL dating on quartz grains (90–125 μm) was performed using the single-aliquot regenerative (SAR) dose protocol [18]. The preheat and cut-heat temperatures were 260 °C and 220 °C, respectively. Here, 12 aliquots were measured for each sample. The equivalent dose of all aliquots was measured with an automated Risø–TL/OSL DA–20 DASH Reader with a combined blue (470 nm, 50 mW/cm2) and infrared (875 nm, 150 mW/cm2) light-emitting diode (LED) unit, and a 90Sr/90Y beta source for irradiation [19]. U, Th, and K concentrations were measured using neutron activation analysis (NAA) at the China Institute of Atomic Energy. Effective dose rate was calculated from elemental concentrations using revised dose rate conversion factors [20]. The computer program Age.exe was used to calculate OSL dates [21]. In order to ensure the accuracy and reliability of the OSL data of the TJW profile, the distribution of the single De value, the dispersion of the natural OSL signal of the sample, and the dispersion of the OSL signal of the first regeneration dose of the sample were analyzed [17,22]. The age-depth relationship was determined using the interpolation method.
4. Results
4.1. Lithology and chronology in TJW profile
Eleven lithological units were identified from the base upwards in the TJW profile (Figs 2, 3), as described in Table 1. Reliable chronology is vitally important for reconstructing paleoclimatic and pedogenic environmental changes, as well as for correlating with other dated records on a time-scale [23]. The ages of loess-paleosol deposits in the upper Hanjiang River are obtained with OSL dating. OSL ages in loess-paleosol profiles at TJW, GXHK, MTS, and QFC sites are presented in Fig 2. The loess-paleosol sequence overlies T1-al1 in the basal part of the TJW profile. OSL samples from the top part of the T1-al1 were dated to 55.11 ± 5.20 ka and 54.65 ± 2.90 ka. The sample from the bottom part of the T1-al2 was dated to 53.48 ± 3.97 ka. The sample from the bottom part of L1 was dated to 53.95 ± 3.84 ka (Figs 2 and 5). Thus, the boundary between T1-al1 and T1-al2 can be constrained to 55.0 ka BP, marking the uplift period of the first terrace of the Hanjiang River and the beginning accumulation of the Malan loess. OSL samples at the bottom of the L1-S2 layer were dated to 27.26 ± 1.44 ka, and at the bottom of L1-S1 layer was dated to 21.59 ± 1.20 ka. Therefore, the results indicates that these two layers were formed about 27.26 ± 1.44 ka BP and 21.59 ± 1.20 ka BP, respectively. OSL samples from the top part of Malan loess (L1-1) were dated to 15.26 ± 1.05 ka (200–205 cm) and 13.57 ± 1.33 ka (190–195 cm). Similar results were observed in the GXHK profile (Fig 2). The L1 is directly covered by the transitional loess (Lt) of the early Holocene. Previous studies have reported that the bottom of the Lt was dated to 10.72 ± 0.39 ka in the MTS profile, and 12.37 ± 0.28 ka in the QFC profile [5,6]. Therefore, the boundary between L1 and Lt can be confined to 11.5 ka BP in the TJW profile.
Paleosol (S0) is widely underlain by Lt of the early Holocene and is buried by recent loess (L0) and Modern soil (MS) of the late Holocene. OSL samples from the top of the Lt were dated to 8.24 ± 0.58 ka in the MTS profile, and 9.68 ± 0.65 ka in the QFC profile. OSL samples from the bottom part of S0 were dated 8.11 ± 0.68 ka in the GXHK profile, and 8.28 ± 0.32 ka in the QFC profile. The boundary between Lt and S0 can be confined to 8.5 ka BP. OSL samples from the top of S0 were dated to 3.35 ± 0.51 ka in the MTS profile, and from the bottom of L0 were dated to 3.09 ± 0.32 ka in the GXHK profile, and 2.90 ± 0.15 ka in the QFC profile. Thus, the major boundary between S0 and L0 can be confined to 3.1 ka BP.
4.2. Vertical distribution of magnetic susceptibility, grain size, loss-on-ignition and geochemical elements in TJW profile
Magnetic susceptibility, grain size composition, and geochemical element changes are consistent with lithological changes (Figs 3, 4) and are described as follows:
Unit 11 (838–818 cm; > 55.0 ka BP). The magnetic susceptibility decreases upward, the sand (>63 μm) exhibits the same trend, i.e., 77.60 × 10−8–97.40 × 10−8 m3·kg-1 and 74.87–85.81%, while clay (<4 μm) and silt (4–63 μm) exhibit the opposite trend (Table 2, Fig 3). Al2O3, Fe2O3, Rb, and Rb/Sr contents increase upward, while Na2O and Sr contents exhibit opposite trends (Table 3, Fig 4).
Unit 10 (818–560 cm; 55.0–36.0 ka BP). Magnetic susceptibility is the lowest value of the whole profile, i.e., 51.09 × 10−8 m3·kg-1 (Table 2), and it increases gradually from bottom to top (Fig 3). The clay content and clay/silt ratio exhibit low values. Fine silt (4–16 μm) and coarse silt (16–63 μm) contents increase markedly compared with unit 11 (Fig 3). The contents of Al2O3, Fe2O3, Rb, and Rb/Sr ratio exhibit the same trend with fine silt, increase markedly compared with unit 11, while Na2O and Sr show opposite trends (Fig 4).
Unit 9 (560–370 cm). The magnetic susceptibility and clay/silt ratio increase slightly compared to unit 10, i.e., 76.15 × 10−8 m3·kg-1 and 0.18 (Table 2). The contents of clay, silt and geochemical element are basically the same with unit 10 (Tables 2 and 3; Figs 3 and 4).
Unit 8 (370–294 cm). Magnetic susceptibility (162.59 × 10−8 m3·kg-1), clay content (15.86%), fine silt (29%), and clay/silt ratio (0.26) increase significantly compared to unit 9. Sand content shows an opposite trend of 21.99% (Table 2, Fig 3). Al2O3, Fe2O3, Rb, and Rb/Sr contents exhibit the same trend with clay and fine silt, with unit 8, while Na2O, CaO and Sr contents exhibit opposite trends (Table 3, Fig 4).
Unit 7 (294–260 cm). Magnetic susceptibility, the contents of clay, fine silt, and clay/silt ratio decrease markedly compared to unit 8. In contrast, the sand content exhibits the opposite trend (Table 2, Fig 3). The contents of Al2O3, Fe2O3, Rb, and Rb/Sr ratio exhibit the same trend as clay and fine silt, increasing with unit 7, while the contents of Na2O, CaO and Sr exhibit opposite trends (Table 3, Fig 4).
Unit 6 (260–228 cm). Magnetic susceptibility, the contents of clay, fine silt, and clay/silt ratio increase markedly compared to unit 7, slightly lower than unit 8 (Fig 3). In contrast, the sand content exhibits the opposite trend (Fig 3). The contents of Al2O3, Fe2O3, Rb, and Rb/Sr ratio exhibit the same trend with clay and fine silt, increasing with unit 7, while the contents of Na2O, CaO and Sr exhibit opposite trends (Table 3; Fig 4).
Unit 5 (228–178 cm; ~ 20–11.5 ka BP) is very similar to units 7 and 9 (Fig 3).
Unit 4 (178–160 cm; 11.5–8.5 ka BP). Magnetic susceptibility, contents of clay, fine silt, and clay/silt ratio increase compared to unit 5 (Fig 3). The contents of Al2O3, Fe2O3, Rb, and Rb/Sr ratio exhibit the same trend as clay and fine silt, increasing with unit 5, while the contents of Na2O, CaO and Sr exhibit opposite trends (Table 3, Fig 4).
Unit 3 (160–66 cm; 8.5–3.1 ka BP). Magnetic susceptibility, the contents of clay, fine silt, coarse silt, and clay/silt ratio increase markedly compared to unit 4, are the high value of the whole profile, i.e., 166.15 × 10−8 m3·kg-1, 14.24%, 31.09%, 30.67%, and 0.28, the sand content varies little within the unit, only 21% (Table 2, Fig 3). The contents of Al2O3, Fe2O3, Rb, and Rb/Sr ratio exhibit the same trend with clay and fine silt, increasing markedly with unit 4, while the contents of Na2O, CaO and Sr exhibit opposite trends (Table 3, Fig 4).
Unit 2 (66–30 cm; 3.1–1.5 ka BP). Magnetic susceptibility, the contents of clay, fine silt, coarse silt, and clay/silt ratio decrease compared to unit 3, sand content increases markedly with unit 3 (Table 2, Fig 3). The contents of Al2O3, Fe2O3, Rb, and Rb/Sr ratio exhibit the same trend with clay and fine silt, decreasing with unit 4, while the contents of Na2O, CaO and Sr exhibit opposite trends (Table 3, Fig 4).
5. Discussion
5.1. Pedogenic intensity change in the TJW profile
Magnetic susceptibility is closely associated with the enrichment of fine-grained ferromagnetic minerals in loess-paleosol profiles [24,25]. It has been widely used as a proxy to reflect pedogenic intensity and paleoclimatic and environmental changes in semi-arid and semi-humid climate regions [26–29]. Generally, higher MS values indicate intensive pedogenesis and a warm and wet climate, while lower values imply weaker pedogenesis and a cold and dry climate [1,30–32]. The magnetic susceptibility values of the TJW profile range from 29.40 × 10-8 to 207.80 × 10-8 m3·kg-1. The S0 layer shows a relatively high value (166.15 × 10-8 m3·kg-1), indicating intensive pedogenesis and the formation of abundant secondary ferromagnetic minerals during 8.5–3.1 ka BP. This suggests warm and humid climate conditions. This is consistent with the middle Holocene Megathermal period [33]. Magnetic susceptibility values in loess (L1-1, L1-2, L1-3) are relatively low, indicating weak pedogenesis and a cold and dry climate. It is noteworthy that in the Malan Loess, the magnetic susceptibility shows one peak around 27 ka and another one around 21 ka (Table 2, Fig 3), with mean values of 139.08 × 10-8 m3·kg-1 and 162.59 × 10-8 m3·kg-1, respectively. These values are higher than those of L1(L1-1, L1-2, L1-3), indicating that these soils underwent a certain degree of pedogenesis and represent weakly developed paleosols. However, the magnetic susceptibility values of L1-S1 and L1-S2 are lower than those of S0, indicating weaker soil formation compared with paleosol S0.
Grain size distribution characteristics of loess are widely used as a surrogate indicator of East Asian monsoon changes [1,4,34–36]. Generally, the content of sand (>63 μm) is used to reflect the rise and fall of the winter monsoon, and the content of clay (<4 μm) indicates the pedogenesis and strength of the summer monsoon [3,37]. The results show that the grain size composition of TJW profile is mainly silt (4–63 μm). In general, the peak clay content occurs in S0 (17.24%), whereas lower mean values (11.12%, 11.30%, 9.99%) are observed in the loess layers (L1-1, L1-2, L1-3). Sand content exhibits the opposite trend to clay in S0 and L1 layers. These characteristics indicate that the S0 underwent intense weathering and pedogenesis and unstable minerals were decomposed to form a large number of fine secondary clay minerals, while loess (L1-1, L1-2, L1-3) underwent weak pedogenesis. At the same time, the grain-size variation curve also shows two distinct peaks around 27 ka and 21 ka (Fig 3), corresponding to the weak paleosol layers L1-S1 and L1-S2. The content of clay (mean value: 13.81% and 15.86%) in the paleosol layer (L1-S1 and L1-S2) is significantly higher than that of loess (L1-1, L1-2, L1-3), but lower than that of S0 (mean value: 17.24%, Table 2), and sand content shows the opposite pattern. These characteristics indicate that the weak paleosols underwent noticeable pedogenic alteration. However, their pedogenic intensity is weaker than that of S0.
The abundances of geochemical elements in aeolian deposits provide critical information on their provenance and on evolutionary characteristics related to weathering and pedogenic intensity [1,38–40]. The enrichment of major elements Al2O3 and Fe2O3 is associated with the formation of secondary clay minerals during weathering and pedogenesis [41]. The enrichment of Rb in paleosol indicates a warm and humid climate, while the higher content of Sr in the loess layers suggests a dry and cold climate [42,43]. The curves of these elements (Al2O3, Fe2O3, Rb) present a similar pattern to the curve of clay content (Figs 3 and 4). Higher concentrations occur in S0 (mean value: 82.5 g/kg, 67.2 g/kg, 111.1 mg/kg) whereas lower concentrations occur in the loess layers (L1-1, L1-2, L1-3). Additionally, the geochemical elements (Al2O3, Fe2O3 and Rb) variation curves show two obvious peaks around 27 ka and 21 ka (Fig 4), corresponding to the weak paleosol layers (L1-S1 and L1-S2). The contents of Al2O3, Fe2O3 and Rb (Table 3, Fig 4) in paleosol layers (L1-S1 and L1-S2) were significantly higher than the contents of Al2O3, Fe2O3 and Rb in loess layers (L1-1, L1-2, L1-3), but lower than these of S0 (Table 2), and the contents of Na2O, CaO, and Sr exhibit the opposite trend, which indicates that the weak paleosol had undergone obvious changes in pedogenesis. However, its weathering intensity is weaker than that of S0.
Based on the analysis of magnetic susceptibility, grain size, and geochemical elements, it can be concluded that the chemical weathering degree of S0 is obviously higher than that of L1 (L1-1, L1-2, L1-3), and the chemical weathering degree of L1-S1 and L1-S2 is also higher than that of L1 (L1-1, L1-2, L1-3).
5.2. MIS 3 and LGM climate fluctuations in the TJW profile
The above analysis shows that the climate in Yunxian county can be divided into four stages, with cold dry (55–11.5 ka) → from cold and dry to warm and humid (11.5–8.5 ka) → warm and humid (8.5–3.1 ka) → from warm and humid to cold and dry (3.1–1.5 ka).
The climate during the L1 stage (55–11.5 ka) was dry and cold, dominated by strong winter winds. It is worth noting that two layers of L1-S2 and L1-S1 in L1 layer indicate two warm and humid periods, which occurred approximately at 27.26 ± 1.44 ka and 21.59 ± 1.20 ka respectively (Fig 5, 6). Considering the location and dating error of the samples, it can be inferred that the formation time of the two layers is about 28.5–21.5 ka BP, indicating that the two relatively warm and humid events occurred in the Hanjiang River region during this period, and there were obvious fluctuations of cold and warm. The formation time of L1-S2 (27.26 ± 1.44 ka) was about the same as that of late MIS 3 in the world, indicating that the warm and humid climate of late MIS 3 was also present in the Hanjiang River region. The formation of L1-S1 (21.59 ± 1.20 ka) may indicate climatic fluctuations during the last glacial maximum. Based on multi-index analysis, the degree of warmth and humidity during these two periods was slightly lower than that during the S0 formation stage (Fig 3, Fig 4). The climate during the Lt stage (11.5–8.5 ka) changed from dry and cold to warm and humid. The S0 stage (8.5–3.1 ka) was the warmest and most humid conditions, as indicated by the intensity of weathering recorded in the TJW profile. The climate in the L0 stage (after 3.1 ka) changed from warm and humid to dry and cold.
(D) The stacked paleo-weathering curve of the loess profiles at Weinan, Luochuan, and Yichuan sites [3]. (E) The magnetic susceptibility variation of the Yuanbao profile in Linxia City [7]. (F) The Rb/Sr ratio variation of the Huining profile in Gansu Province [8]. (G). The content of δ18O in Guliya ice core [47].
5.3. MIS 3 climate events and regional comparison recorded in TJW profile
Climate change trends towards relatively warm and humid conditions during MIS 3 have been recorded in many other regions of the world [44,45]. For instance, in the northwest region where there are significant differences in precipitation, temperature and the upper reaches of the Hanjiang River, similar climate fluctuation phenomena similar to those observed in the MIS3 stage of the TJW profile were also recorded [7,8]. According to paleo-weathering curves of loess profiles in Luochuan and other places, MIS 3 can be roughly divided into three warm and wet stages and two cold and dry stages, but the temperature and humidity degree of the late stage is weaker than that of the early stage [3] (Fig 6). The study of Yuanbao profile in Linxia county (Fig 6) shows that climate in this period can be divided into five stages, with high temperature and humidity (56.1–42.2 ka) → cold dried (42.2–39.3 ka) → mild temperature (39.3–33.1 ka) → cold dry (33.1–31.0 ka) → medium isothermal wet (31.0–25.0 ka), the temperature and humidity of the late stage in MIS 3 was lower than that of the early stage [7]. The MIS 3 climate recorded from the Huining profile in Gansu Province (Fig 6) can be divided into three stages: low temperature and humidity (55.5–45.9 ka) → dry cold (45.9–27.3 ka) → high temperature (27.3–23.8 ka), the temperature and humidity degree of the late period is higher than that of the early period [8]. Although there are climatic differences between the northwest region and the upper reaches of the Hanjiang River, due to the influence of the regional atmospheric circulation pattern, the overall soil formation process remains similar. In addition, ice-cores also recorded the climate fluctuation phenomena during the MIS 3 period [46–48]. For example, δ18O studies from Greenland ice-cores indicate that climate during the MIS 3 is anomalous and warm [46,47]. The Gurilya ice core also records that there were two periods of climate warming during MIS 3 [48]. Zheng et al selected three sedimentary cores with relatively high and continuous sedimentation rates in the north, west and south of the South China Sea as their research subjects. They revealed that there were multiple rapid climate change events during the MIS 3 period [49]. Johan et al conducted a study on the sediments of the Scandinavian Peninsula, and the results showed that from 55 ka to 35 ka, it was an ice retreat period, and then the ice sheet began to expand [50]. It indicates that there were fluctuations in temperature during the MIS 3 period.
In conclusion, the MIS 3 recorded in the TJW profile represents a specific response of this region to global climate change. It is found that climate change records of MIS 3 period are not identical among different sites. It is speculated that these differences mainly exist in the following aspects: First, the upper reaches of the Hanjiang River are located in the south of the Qinling Mountains, which is the intersection area of various monsoon/air masses (East Asian summer monsoon, Indian monsoon), and its hydrothermal configuration is different from that of the Loess Plateau dominated by the pure East Asian monsoon. The second is the terrain effect: the barrier effect of Qinling Mountains may weaken the influence of cold air in the north, and may also modulate the water vapor transport. The third is the sensitivity of alternative indicators: discuss the possible differences in the climatic significance of the same indicator (such as magnetic susceptibility) in different climatic regions. The relevance of our findings to global records such as the Guliya ice core suggests that it is both a response to global signals and has regional characteristics.
6. Conclusion
An in-depth survey was carried out on the first terrace of the Hanjiang River valley, and a loess-paleosol profile was identified. Multi-proxy analysis was used to reconstruct the climate changes recorded in this profile during MIS 3. The main conclusions are as follows:
- Chemical weathering of S0 is the strongest in the formation period, and the weathering of Malan loess is weak in the formation period, but the weathering of Malan loess is stronger in the depths of 228–260 cm and 294–370 cm, and the pedogenesis is obvious. It belongs to weak a paleosol layer (L1-S1 and L1-S2).
- Malan Loess layer indicates that the climate was dry and cold. Weak paleosol layers (L1-S1 and L1-S2) suggest that the climate was not continuously dry and cold during late MIS 3. There are two periods of warm and humid climate during about 28.5–21.5 ka. Loess (Lt) indicates that the climate changes from dry-cold to warm-wet.
- There are significant differences in the manifestation and intensity of the relative warm and humid climate in the MIS 3 between the north and south of China. The upper reaches of the Hanjiang River may record the unique information of the interaction between the East Asian monsoon system and the middle and low latitude climate system.
Supporting information
S1 File. Dataset of Magnetic Susceptibility and Grain Size from the Tuojiawan Profile.
https://doi.org/10.1371/journal.pone.0341061.s001
(XLSX)
S2 File. Dataset of Geochemical Elements from the Tuojiawan Profile.
https://doi.org/10.1371/journal.pone.0341061.s002
(XLSX)
References
- 1.
Liu T. Loess and the Environment. Science Press, Beijing, 1985.
- 2. An Z, Lu Y. Climate and stratigraphy of the Malan loess of late Pleistocene in northern China. Chinese Sci Bull. 1984;29:228–31.
- 3. Guo Z, Liu T, Guiot J, Wu N, Lü H, Han J, et al. High frequency pulses of East Asian monsoon climate in the last two glaciations: Link with the North Atlantic. Climate Dynamics. 1996;12(10):701–9.
- 4. Ding ZL, Derbyshire E, Yang SL, Yu ZW, Xiong SF, Liu TS. Stacked 2.6‐Ma grain size record from the Chinese loess based on five sections and correlation with the deep‐sea δ18O record. Paleoceanography. 2002;17(3).
- 5. Mao P, Pang J, Huang C, Zha X, Zhou Y, Guo Y, et al. A multi-index analysis of the extraordinary paleoflood events recorded by slackwater deposits in the Yunxi Reach of the upper Hanjiang River, China. CATENA. 2016;145:1–14.
- 6. Mao P, Pang J, Huang C, Zha X, Zhou Y, Guo Y. Loess deposits of the upper Hanjiang River valley, south of Qinling Mountains, China: Implication for the pedogenic dynamics controlled by paleomonsoon climate evolution. Aeolian Research. 2017;25:63–77.
- 7. Chen Y, Rao Z, Zhang J, Chen X. Comparative study of MIS 3 climatic features recorded in Malan loess in the western part of the Loess Plateau and global records. Quat Sci. 2004;24:359–65.
- 8. Zhai X, Wu S, Li F. Geochemistry characteristics of elements in loess in the Huining profile in MIS 3 and climate change. Arid Zone Res. 2013;30:156–61.
- 9. Zhang X, Zhou A, Zhang C, Hao S, Zhao Y, An C. High‐resolution records of climate change in arid eastern central Asia during MIS 3 (51 600–25 300 cal a BP) from Wulungu Lake, north‐western China. J Quaternary Science. 2016;31(6):577–86.
- 10. Guo Y, Huang CC, Pang J, Zha X, Zhou Y, Zhang Y, et al. Sedimentological study of the stratigraphy at the site of Homo erectus yunxianensis in the upper Hanjiang River valley, China. Quaternary International. 2013;300:75–82.
- 11. Guo Y, Huang CC, Pang J, Zha X, Zhou Y, Wang L, et al. Investigating extreme flood response to Holocene palaeoclimate in the Chinese monsoonal zone: A palaeoflood case study from the Hanjiang River. Geomorphology. 2015;238:187–97.
- 12. Bian H, Pang J, Huang C, Zhang W. The response of transitional pedogenic characteristics of loess in the Yunxian Basin to abrupt climatic events in the northern subtropics since the Last Glacial Maximum. CATENA. 2018;171:166–75.
- 13. Huang CC, Pang J, Zha X, Zhou Y, Yin S, Su H, et al. Extraordinary hydro-climatic events during the period AD 200−300 recorded by slackwater deposits in the upper Hanjiang River valley, China. Palaeogeography, Palaeoclimatology, Palaeoecology. 2013;374:274–83.
- 14. Zhang Y, Huang CC, Pang J, Zha X, Zhou Y, Gu H. Holocene paleofloods related to climatic events in the upper reaches of the Hanjiang River valley, middle Yangtze River basin, China. Geomorphology. 2013;195:1–12.
- 15. Shen Y. The formation and evolution of landforms in the Han River valley. Acta Geograph Sin. 1956;22:295–322.
- 16. Pang J, Huang C, Zhou Y, Zha X. Eolian loess-paleosol sequence and OSL age of the first terraces within the Yunxi Basin along the upper Hanjiang River China. Acta Geograph Sin. 2015;70:63–71.
- 17. Zhang W, Pang J, Huang C, Zhou Y, Zha X, Cui T, et al. OSL daring of TJW section in the Upper Hangjiang River Valley and its environment significance. J Desert Research. 2017;37:885–92.
- 18. Murray AS, Wintle AG. Luminescence dating of quartz using an improved single-aliquot regenerative-dose protocol. Radiation Measurements. 2000;32(1):57–73.
- 19. Bøtter-Jensen L, Duller GAT. A new system for measuring optically stimulated luminescence from quartz samples. International Journal of Radiation Applications and Instrumentation Part D Nuclear Tracks and Radiation Measurements. 1992;20(4):549–53.
- 20. Adamiec G, Aitken MJ. Dose-rate conversion factors: update. ATL. 1998;16(2):37–50.
- 21.
Grün R. The age.exe computer program for the calculation of luminescence dates. Canberra: RSES. 2003.
- 22. Pang J, Huang C, Zhou Y, Zha X, Zhang W, Cui T, et al. Luminescence dating and stratigraphic chronology of Tuojiawan profile in Hubei and recorded 55 ka BP climate change. Acta Geologica Sinica. 2017;91:2841–53.
- 23. Porter SC. Chinese loess record of monsoon climate during the last glacial–interglacial cycle. Earth-Science Reviews. 2001;54(1–3):115–28.
- 24. Heller F, Liu T. Palaeoclimatic and sedimentary history from magnetic susceptibility of loess in China. Geophys Res Lett. 1986;13:1169–72.
- 25.
Thompson R, Oldfield F. Environmental magnetism. Beijing: Geological Publishing House. 1995.
- 26. Maher BA. Magnetic properties of modern soils and Quaternary loessic paleosols: paleoclimatic implications. Palaeogeography, Palaeoclimatology, Palaeoecology. 1998;137(1–2):25–54.
- 27. Hao Q, Oldfield F, Bloemendal J, Guo Z. The magnetic properties of loess and paleosol samples from the Chinese Loess Plateau spanning the last 22 million years. Palaeogeography, Palaeoclimatology, Palaeoecology. 2008;260:389–404.
- 28. Zhang W, Dong C, Ye L, Ma H, Yu L. Magnetic properties of coastal loess on the Midao islands, northern China: Implications for provenance and weathering intensity. Palaeogeography, Palaeoclimatology, Palaeoecology. 2012;333–334:160–7.
- 29. Buggle B, Hambach U, Müller K, Zöller L, Marković SB, Glaser B. Iron mineralogical proxies and Quaternary climate change in SE-European loess–paleosol sequences. Catena. 2014;117:4–22.
- 30. An Z, Kukla G, Liu T. Loess stratigraphy in Luochuan of China. Quat Sci. 1989;2:157–68.
- 31. Liu X. Pedogenic modification of magnetic susceptibility signals recording paleoclimate – an explanation of regional changes to Alaskan, Chinese and Siberian loess. Quaternary International. 2012;279–280:283.
- 32. Bloemendal J, Liu X, Sun Y, Li N. An assessment of magnetic and geochemical indicators of weathering and pedogenesis at two contrasting sites on the Chinese Loess plateau. Palaeogeography, Palaeoclimatology, Palaeoecology. 2008;257(1–2):152–68.
- 33. Wang H, Chen J, Zhang X, Chen F. Palaeosol development in the Chinese Loess Plateau as an indicator of the strength of the East Asian summer monsoon: Evidence for a mid-Holocene maximum. Quaternary International. 2014;334–335:155–64.
- 34.
Kutzbach JE, Guetter PJ, Behling PJ, Selin R. Simulated climatic changes: Results of the COHMAP climate-model experiments. Wright HE, Kutzbach JE, Webb ZT, Ruddiman WF, Street-Perrott FA, Bartlein PJ. Global climates since the last glacial maximum. Minneapolis, MN: Univ Minnesota Press. 1993. 24–93.
- 35. Xiao J, Porter SC, An Z, Kumai H, Yoshikawa S. Grain size of quartz as an indicator of winter monsoon strength on the loess plateau of central China during the Last 130,000 Yr. Quat res. 1995;43(1):22–9.
- 36. Farrell EJ, Sherman DJ, Ellis JT, Li B. Vertical distribution of grain size for wind blown sand. Aeolian Research. 2012;7:51–61.
- 37. Zhao S, Liu Z, Colin C, Zhao Y, Wang X, Jian Z. Responses of the East Asian summer monsoon in the low‐latitude South China sea to high‐latitude millennial‐scale climatic changes during the last glaciation: Evidence from a high‐resolution clay mineralogical record. Paleoceanog and Paleoclimatol. 2018;33(7):745–65.
- 38. Jahn B, Gallet S, Han J. Geochemistry of the Xining, Xifeng and Jixian sections, Loess Plateau of China: eolian dust provenance and paleosol evolution during the last 140 ka. Chemical Geology. 2001;178(1–4):71–94.
- 39. Hao Q, Guo Z, Qiao Y, Xu B, Oldcfield F. Geochemical evidence for the provenance of middle Pleistocene loess deposits in southern China. Quat. Sci. Rev. 2010, 29, 3317–26.
- 40. Qiao Y, Hao Q, Peng S, Wang Y, Li J, Liu Z. Geochemical characteristics of the eolian deposits in southern China, and their implications for provenance and weathering intensity. Palaeogeography, Palaeoclimatology, Palaeoecology. 2011;308(3–4):513–23.
- 41. Gallet S, Jahn B, Torii M. Geochemical characterization of the Luochuan loess-paleosol sequence, China, and paleoclimatic implications. Chemical Geology. 1996;133(1–4):67–88.
- 42. Diao G, Wen Q, Wu M, Pan J. Study on the average contents and correlativity of trace elements in Malan Loess from the middle reaches of the Yellow River. Mar Geol Quat Geol. 1996; 16: 85–92.
- 43. Roy I, Gandhi N. Trace element variations in Indian speleothems: Insights into the Holocene climate. Quaternary International. 2024;709:55–65.
- 44. Grigg LD, Whitlock C, Dean WE. Evidence for Millennial-Scale Climate Change During Marine Isotope Stages 2 and 3 at Little Lake, Western Oregon, U.S.A. Quat res. 2001;56(1):10–22.
- 45. Woronko B, Karasiewicz TM, Rychel J, Kupryjanowicz M, Fiłoc M, Moska P, et al. A palaeoenvironmental record of MIS 3 climate change in NE Poland—Sedimentary and geochemical evidence. Quaternary International. 2022;617:80–100.
- 46. Mogensen IA, Johnsen SJ, Ganopolski A, Rahmstorf S. An investigation of rapid warm transitions during MIS2 and MIS3 using Greenland ice-core data and the CLIMBER-2 model. Ann Glaciol. 2002;35:398–402.
- 47. Rousseau D-D, Boers N, Sima A, Svensson A, Bigler M, Lagroix F, et al. (MIS3 & 2) millennial oscillations in Greenland dust and Eurasian aeolian records – A paleosol perspective. Quaternary Science Reviews. 2017;169:99–113.
- 48. Shi Y, Yao T, Yang B. Climate change on a scale of 10 years in the Guliya ice core over nearly 2,000 years and its comparison with the documentary records in eastern China. Science in China (Series D). 1999;S1:79–86.
- 49. Zheng H, Yang W, He J, Mei X, Chen G, Xie X, et al. Marine Isotope Stage 3 (MIS3) of South China Sea. Quaternary Sci. 2008;28:68–78.
- 50. Kleman J, Hättestrand M, Borgström I, Fabel D, Preusser F. Age and duration of a MIS 3 interstadial in the Fennoscandian Ice Sheet core area – Implications for ice sheet dynamics. Quaternary Science Reviews. 2021;264:107011.