Pub Date : 2025-01-28DOI: 10.1016/j.palaeo.2025.112783
Qiaoyi Ma , Yusheng (Chris) Liu , Qijia Li , Cheng Quan
There is still much debate on the origin, development, and evolution of the Asian monsoon system, particularly regarding its form and time period. The present study used the Climate Leaf Analysis Multivariate Program to statistically reconstruct the late Early Oligocene climate of Baise, Guangxi, low-latitude China, based on the Fuping flora. The results suggest that Baise's mean annual temperature (MAT) during in the Oligocene was 20.5 ± 2.3 °C, which is lower than its current MAT of 22.9 °C. Baise's paleogeographical relocation and modern topography, which is influenced by the Föhn effect, might be the cause of the variation in MATs. With monsoon indices of 3.27 and 8.61, respectively, the precipitation ratio of 3-WET to 3-DRY months indicates a weaker monsoon during the Oligocene than it does now. Furthermore, our results for the vegetation show that the Fuping flora's leaf physiognomy spectrum has a spatial distribution that is comparable to that of the Transition Area (TA) of East Asian Monsoon (EAM) and South Asian Monsoon (SAM), with an inclination toward the SAM zone. This implies that the SAM was formed in Baise by the late Early Oligocene, which may have something to do with the uplift of the Tibetan Plateau and the retreat of the Paratethys Sea. The enhanced cooling at high latitudes was probably caused by the transition from TA-SAM to EAM and the correspondingly stronger monsoon from the late Early Oligocene to the present periods of Baise.
{"title":"Early Oligocene Asian monsoon: Evidence from the Fuping flora of Baise, Guangxi, low-latitude China","authors":"Qiaoyi Ma , Yusheng (Chris) Liu , Qijia Li , Cheng Quan","doi":"10.1016/j.palaeo.2025.112783","DOIUrl":"10.1016/j.palaeo.2025.112783","url":null,"abstract":"<div><div>There is still much debate on the origin, development, and evolution of the Asian monsoon system, particularly regarding its form and time period. The present study used the Climate Leaf Analysis Multivariate Program to statistically reconstruct the late Early Oligocene climate of Baise, Guangxi, low-latitude China, based on the Fuping flora. The results suggest that Baise's mean annual temperature (MAT) during in the Oligocene was 20.5 ± 2.3 °C, which is lower than its current MAT of 22.9 °C. Baise's paleogeographical relocation and modern topography, which is influenced by the Föhn effect, might be the cause of the variation in MATs. With monsoon indices of 3.27 and 8.61, respectively, the precipitation ratio of 3-WET to 3-DRY months indicates a weaker monsoon during the Oligocene than it does now. Furthermore, our results for the vegetation show that the Fuping flora's leaf physiognomy spectrum has a spatial distribution that is comparable to that of the Transition Area (TA) of East Asian Monsoon (EAM) and South Asian Monsoon (SAM), with an inclination toward the SAM zone. This implies that the SAM was formed in Baise by the late Early Oligocene, which may have something to do with the uplift of the Tibetan Plateau and the retreat of the Paratethys Sea. The enhanced cooling at high latitudes was probably caused by the transition from TA-SAM to EAM and the correspondingly stronger monsoon from the late Early Oligocene to the present periods of Baise.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"662 ","pages":"Article 112783"},"PeriodicalIF":2.6,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-28DOI: 10.1016/j.palaeo.2025.112771
Fukang Wei , Yajie Dong , Naiqin Wu , Fengjiang Li , Houyuan Lu
Snails, as common indicator species, have been widely used to reconstruct past climatic and environmental changes. However, whether their relationships with climate have changed over time has not been systematically investigated. This study integrates modern and fossil data to assess the stability of snail-climate relationships of dominant snail species in Chinese loess deposits since the Last Glacial Maximum. Using boosted regression trees (BRT) and local polynomial regression (LOESS), we analyzed the optimal summer temperature and precipitation response ranges of dominant snail species across five time-intervals (18–12 ka, 12–6 ka, 6–2 ka, 2 ka to present, and the present). The results show that different snail species exhibit varying preferred climatic ranges, consistent with their respective ecological types. Despite these ecological differences, their climatic ranges have shown no significant changes across the five periods, indicating a general similar pattern of snail-climate associations. For instance, Vallonia tenera exhibits its strongest response at summer temperatures of ∼12–15 °C and precipitation below ∼100 mm/month across the five periods, while Macrochlamys angigyra exhibits peak responses to summer temperatures exceeding ∼15 °C and precipitation levels of ∼120–150 mm/month. Furthermore, species differ in their dependence on summer temperature and precipitation, with V. tenera more reliant on precipitation, and M. angigyra and Opeas striatissimum more sensitive to temperature across all time intervals. Overall, the stability of these snail-climate relationships since the Last Glacial Maximum confirms their use as paleoclimate proxies, and their differing climatic dependencies offers valuable insights for climate reconstructions.
{"title":"Assessing the temporal stability of snail-climate relationships since the Last Glacial Maximum: Insights from boosted regression trees and LOESS models","authors":"Fukang Wei , Yajie Dong , Naiqin Wu , Fengjiang Li , Houyuan Lu","doi":"10.1016/j.palaeo.2025.112771","DOIUrl":"10.1016/j.palaeo.2025.112771","url":null,"abstract":"<div><div>Snails, as common indicator species, have been widely used to reconstruct past climatic and environmental changes. However, whether their relationships with climate have changed over time has not been systematically investigated. This study integrates modern and fossil data to assess the stability of snail-climate relationships of dominant snail species in Chinese loess deposits since the Last Glacial Maximum. Using boosted regression trees (BRT) and local polynomial regression (LOESS), we analyzed the optimal summer temperature and precipitation response ranges of dominant snail species across five time-intervals (18–12 ka, 12–6 ka, 6–2 ka, 2 ka to present, and the present). The results show that different snail species exhibit varying preferred climatic ranges, consistent with their respective ecological types. Despite these ecological differences, their climatic ranges have shown no significant changes across the five periods, indicating a general similar pattern of snail-climate associations. For instance, <em>Vallonia tenera</em> exhibits its strongest response at summer temperatures of ∼12–15 °C and precipitation below ∼100 mm/month across the five periods, while <em>Macrochlamys angigyra</em> exhibits peak responses to summer temperatures exceeding ∼15 °C and precipitation levels of ∼120–150 mm/month. Furthermore, species differ in their dependence on summer temperature and precipitation, with <em>V. tenera</em> more reliant on precipitation, and <em>M. angigyra</em> and <em>Opeas striatissimum</em> more sensitive to temperature across all time intervals. Overall, the stability of these snail-climate relationships since the Last Glacial Maximum confirms their use as paleoclimate proxies, and their differing climatic dependencies offers valuable insights for climate reconstructions.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"662 ","pages":"Article 112771"},"PeriodicalIF":2.6,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148620","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-28DOI: 10.1016/j.palaeo.2025.112781
Haixin Lu , Fucai Duan , Zhenqiu Zhang , Jianshun Chen , Junji Zhu , Qingfeng Shao , Yongjin Wang
Characterization of the Asian summer monsoon (ASM) during the Last Glacial Maximum (LGM) would significantly improve our understanding of ASM dynamics in the current interglacial period. However, the variability of the ASM and its global teleconnection during the LGM remain unclear. Here we offer high-resolution δ13C and rather coarse Mg/Ca data from a stalagmite in southern China spanning 23.1 to 19.3 ka. This high-resolution δ13C record, generally corroborated by the Mg/Ca record, reveals an increase in ASM precipitation in southern China during 22–21 ka, a period of rapid growth in global ice volume. We propose that the high ASM precipitation was associated with the additional southward migration of the ASM rain belt and the strengthening of the Atlantic Meridional Overturning Circulation notwithstanding the significant ice accumulation. Furthermore, we show that the LGM was characterized by centennial and multi-centennial oscillations common to the Holocene Thermal Maximum (HTM). The common oscillations between the two different periods show that they are independent of global ice volume. Further studies show that the multi-centennial oscillations during the LGM are associated with changes in air temperature over Antarctica and sea surface temperature in the southeastern and tropical Pacific. These relationships demonstrate the influence of Antarctic temperature and El Niño-Southern Oscillation (ENSO) variability on ASM precipitation on the multi-centennial scale during the LGM. In conclusion, our analysis shows that the multi-scale changes in ASM precipitation in southern China are related to conditions in the ocean circulation and ENSO mode during the LGM. The persistent multi-centennial variations between the LGM and HTM indicate that the multi-centennial scale may be a viable window for estimating future ASM precipitation in southern China.
{"title":"Hydroclimate variability over East Asia linked to ocean circulation, Antarctic and Pacific temperature changes during the LGM","authors":"Haixin Lu , Fucai Duan , Zhenqiu Zhang , Jianshun Chen , Junji Zhu , Qingfeng Shao , Yongjin Wang","doi":"10.1016/j.palaeo.2025.112781","DOIUrl":"10.1016/j.palaeo.2025.112781","url":null,"abstract":"<div><div>Characterization of the Asian summer monsoon (ASM) during the Last Glacial Maximum (LGM) would significantly improve our understanding of ASM dynamics in the current interglacial period. However, the variability of the ASM and its global teleconnection during the LGM remain unclear. Here we offer high-resolution δ<sup>13</sup>C and rather coarse Mg/Ca data from a stalagmite in southern China spanning 23.1 to 19.3 ka. This high-resolution δ<sup>13</sup>C record, generally corroborated by the Mg/Ca record, reveals an increase in ASM precipitation in southern China during 22–21 ka, a period of rapid growth in global ice volume. We propose that the high ASM precipitation was associated with the additional southward migration of the ASM rain belt and the strengthening of the Atlantic Meridional Overturning Circulation notwithstanding the significant ice accumulation. Furthermore, we show that the LGM was characterized by centennial and multi-centennial oscillations common to the Holocene Thermal Maximum (HTM). The common oscillations between the two different periods show that they are independent of global ice volume. Further studies show that the multi-centennial oscillations during the LGM are associated with changes in air temperature over Antarctica and sea surface temperature in the southeastern and tropical Pacific. These relationships demonstrate the influence of Antarctic temperature and El Niño-Southern Oscillation (ENSO) variability on ASM precipitation on the multi-centennial scale during the LGM. In conclusion, our analysis shows that the multi-scale changes in ASM precipitation in southern China are related to conditions in the ocean circulation and ENSO mode during the LGM. The persistent multi-centennial variations between the LGM and HTM indicate that the multi-centennial scale may be a viable window for estimating future ASM precipitation in southern China.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"662 ","pages":"Article 112781"},"PeriodicalIF":2.6,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148621","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-28DOI: 10.1016/j.palaeo.2025.112779
Kristine Steinsland , Danielle M. Grant , Kirsten Fahl , Ruediger Stein , Tine L. Rasmussen , Bjørg Risebrobakken , Ulysses S. Ninnemann , Jochen Knies , Julie Heggdal Velle , Stijn De Schepper
The ongoing reduction of Arctic sea ice underscores the need to understand the drivers behind sea ice variability and associated ocean-climate impacts. The Last Interglacial, Marine Isotope (sub)Stage (MIS) 5e, and its transitions offer insights into sea ice variability during a period warmer than pre-industrial, and intervals of large climatic changes. This study examines a marine sediment core from the eastern Fram Strait, covering late MIS 6 to early MIS 5b (140–90 ka). We analysed organic biomarkers, including the PIP25 sea ice index and dinoflagellate cyst assemblages, complemented by stable oxygen isotopes, total organic carbon, and sediment physical properties (ice rafted debris, X-ray fluorescence, magnetic susceptibility). Our findings demonstrate a progression from extensive sea ice cover during late MIS 6 to a marginal ice zone during Termination II (T II) and open ocean conditions during MIS 5e, influenced by the Svalbard–Barents Sea Ice Sheet (SBIS) and warm Atlantic surface waters, superimposed on the gradual changes in Northern Hemisphere summer insolation. During late MIS 6, intermittent local polynyas formed by katabatic winds and Atlantic water intrusions temporarily disrupted the sea ice cover. During T II, the marginal ice zone environment, combined with organic matter-rich meltwater influx from the retreating SBIS may have enhanced the biological pump. MIS 5e exhibited a “two-step” warming with the strongest influence of Atlantic waters around ∼120 ka. Low to absent concentrations of biomarkers and dinoflagellate cysts immediately following MIS 5e complicate interpretations of sea ice and oceanic conditions during MIS 5d to MIS 5c, a crucial climatic interval characterised by periods with Northern Hemisphere summer insolation values comparable to today. These findings highlight the complexities of understanding Arctic sea ice responses to ocean-climate drivers and the need for further investigation into the unresolved MIS 5 proxy signals, important for improving our understanding of future sea ice decline and the associated ocean-climate impacts.
{"title":"Sea ice variability from the penultimate glacial to the last interglacial in the eastern Fram Strait","authors":"Kristine Steinsland , Danielle M. Grant , Kirsten Fahl , Ruediger Stein , Tine L. Rasmussen , Bjørg Risebrobakken , Ulysses S. Ninnemann , Jochen Knies , Julie Heggdal Velle , Stijn De Schepper","doi":"10.1016/j.palaeo.2025.112779","DOIUrl":"10.1016/j.palaeo.2025.112779","url":null,"abstract":"<div><div>The ongoing reduction of Arctic sea ice underscores the need to understand the drivers behind sea ice variability and associated ocean-climate impacts. The Last Interglacial, Marine Isotope (sub)Stage (MIS) 5e, and its transitions offer insights into sea ice variability during a period warmer than pre-industrial, and intervals of large climatic changes. This study examines a marine sediment core from the eastern Fram Strait, covering late MIS 6 to early MIS 5b (140–90 ka). We analysed organic biomarkers, including the PIP<sub>25</sub> sea ice index and dinoflagellate cyst assemblages, complemented by stable oxygen isotopes, total organic carbon, and sediment physical properties (ice rafted debris, X-ray fluorescence, magnetic susceptibility). Our findings demonstrate a progression from extensive sea ice cover during late MIS 6 to a marginal ice zone during Termination II (T II) and open ocean conditions during MIS 5e, influenced by the Svalbard–Barents Sea Ice Sheet (SBIS) and warm Atlantic surface waters, superimposed on the gradual changes in Northern Hemisphere summer insolation. During late MIS 6, intermittent local polynyas formed by katabatic winds and Atlantic water intrusions temporarily disrupted the sea ice cover. During T II, the marginal ice zone environment, combined with organic matter-rich meltwater influx from the retreating SBIS may have enhanced the biological pump. MIS 5e exhibited a “two-step” warming with the strongest influence of Atlantic waters around ∼120 ka. Low to absent concentrations of biomarkers and dinoflagellate cysts immediately following MIS 5e complicate interpretations of sea ice and oceanic conditions during MIS 5d to MIS 5c, a crucial climatic interval characterised by periods with Northern Hemisphere summer insolation values comparable to today. These findings highlight the complexities of understanding Arctic sea ice responses to ocean-climate drivers and the need for further investigation into the unresolved MIS 5 proxy signals, important for improving our understanding of future sea ice decline and the associated ocean-climate impacts.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"663 ","pages":"Article 112779"},"PeriodicalIF":2.6,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143355561","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-28DOI: 10.1016/j.palaeo.2025.112777
Jessica A. Jacobs , Julie N. Richey , Jennifer A. Flannery , Kaustubh Thirumalai , Lauren T. Toth
Large-scale Holocene climate reconstructions rely heavily on extratropical proxy records. Coral-based temperature reconstructions from the tropical and subtropical oceans therefore fill a critical spatial and temporal data gap, allowing for reconstruction of seasonally resolved temperature variability. We present five new, monthly-resolved sea-surface temperature (SST) reconstructions (between 39 and 57 years in length) from 2 to 7 thousand years ago (ka) based on the strontium-to‑calcium ratio (Sr/Ca) of Orbicella faveolata corals from subtropical reefs in south Florida. Modern calibrations between O. faveolata Sr/Ca and in situ SST from the region allow us to directly compare the mean and variability of SSTs since the mid-Holocene. In contrast to the low climate variability observed in more tropical areas of the western Atlantic during the Holocene, our records from subtropical south Florida exhibit pronounced changes in mean SST and variability. Our records suggest that mid-Holocene SSTs in the Florida Keys were highly variable, with relatively cooler winters driving a cooler mean SST at ∼6.7 ka (23.7 ± 0.6°C at 6.7 ka and 25.0 ± 0.5°C at 6.6 ka), and relatively warmer summers and more variable temperatures by 5.8 ka (27.1 ± 0.4°C, seasonality of 8.7°C). We also analyzed stable oxygen isotopes in two of our corals and those data support our Sr/Ca-based estimate of climatic warming between 6.6 ka and 5.8 ka (−3.6‰ and − 3.9‰). Both winter and summer temperatures were significantly cooler than the other mid-to-late Holocene snapshots at 3.6 ka (21.2 ± 0.5°C) and SST warmed but remained highly variable at 2.6 ka (25.0 ± 0.6°C, seasonality of 7.9°C). These centennial-scale changes in climate variability potentially contributed to the regional shutdown of reef accretion by the late Holocene. Our reconstructions provide a proof-of-concept study that highlights the value of coral-based SST records from highly sensitive, subtropical locations for understanding Holocene climate on seasonal to centennial timescales.
{"title":"Snapshots of mid-to-late Holocene sea-surface temperature variability from a subtropical western Atlantic coral reef","authors":"Jessica A. Jacobs , Julie N. Richey , Jennifer A. Flannery , Kaustubh Thirumalai , Lauren T. Toth","doi":"10.1016/j.palaeo.2025.112777","DOIUrl":"10.1016/j.palaeo.2025.112777","url":null,"abstract":"<div><div>Large-scale Holocene climate reconstructions rely heavily on extratropical proxy records. Coral-based temperature reconstructions from the tropical and subtropical oceans therefore fill a critical spatial and temporal data gap, allowing for reconstruction of seasonally resolved temperature variability. We present five new, monthly-resolved sea-surface temperature (SST) reconstructions (between 39 and 57 years in length) from 2 to 7 thousand years ago (ka) based on the strontium-to‑calcium ratio (Sr/Ca) of <em>Orbicella faveolata</em> corals from subtropical reefs in south Florida. Modern calibrations between <em>O. faveolata</em> Sr/Ca and in situ SST from the region allow us to directly compare the mean and variability of SSTs since the mid-Holocene. In contrast to the low climate variability observed in more tropical areas of the western Atlantic during the Holocene, our records from subtropical south Florida exhibit pronounced changes in mean SST and variability. Our records suggest that mid-Holocene SSTs in the Florida Keys were highly variable, with relatively cooler winters driving a cooler mean SST at ∼6.7 ka (23.7 ± 0.6°C at 6.7 ka and 25.0 ± 0.5°C at 6.6 ka), and relatively warmer summers and more variable temperatures by 5.8 ka (27.1 ± 0.4°C, seasonality of 8.7°C). We also analyzed stable oxygen isotopes in two of our corals and those data support our Sr/Ca-based estimate of climatic warming between 6.6 ka and 5.8 ka (−3.6‰ and − 3.9‰). Both winter and summer temperatures were significantly cooler than the other mid-to-late Holocene snapshots at 3.6 ka (21.2 ± 0.5°C) and SST warmed but remained highly variable at 2.6 ka (25.0 ± 0.6°C, seasonality of 7.9°C). These centennial-scale changes in climate variability potentially contributed to the regional shutdown of reef accretion by the late Holocene. Our reconstructions provide a proof-of-concept study that highlights the value of coral-based SST records from highly sensitive, subtropical locations for understanding Holocene climate on seasonal to centennial timescales.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"663 ","pages":"Article 112777"},"PeriodicalIF":2.6,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143098196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-28DOI: 10.1016/j.palaeo.2025.112780
Tianran Chen , Guoqiao Xiao , Qing Pan , Qian Wang , Huiru Xu
Magnetostratigraphic dating is an important method for establishing the chronological framework of Chinese loess. However, the positions of geomagnetic polarity boundaries and anomalous geomagnetic excursions have been reported inconsistently across different loess sections. Previous studies have questioned the fidelity of the primary remanent magnetization recorded by coarse loess layers, as it may be influenced by remagnetization processes during subsequent geomagnetic reversals. In this study, we simulated magnetic field reversals in the laboratory to investigate their effect on paleomagnetic records in Middle and Late Pleistocene loess and paleosol samples from the western and southeastern Chinese Loess Plateau (CLP). The results reveal that: 1) Remagnetization processes are more likely to occur in surface subsamples from the same block of loess compared to interior subsamples, while such phenomena are rare in paleosol samples. 2) Individual specimens from the western CLP are more prone to exhibiting anomalous remanent magnetization components, suggesting that coarser and more porous samples are more susceptible to recording erratic paleomagnetic information. 3) Secondary remanent magnetization acquired in the laboratory is unstable and exhibits varied thermal demagnetization behaviors among individual subsamples. These observations suggest that the reliability of short geomagnetic reversals, as well as the transition processes and behaviors recorded in Chinese loess, should be carefully re-evaluated. The effects of remagnetization cannot be ignored when investigating the magnetostratigraphy of Chinese loess.
{"title":"An experimental assessment on the stability of remanent magnetization of Chinese loess and implications for the loess magnetostratigraphy investigations","authors":"Tianran Chen , Guoqiao Xiao , Qing Pan , Qian Wang , Huiru Xu","doi":"10.1016/j.palaeo.2025.112780","DOIUrl":"10.1016/j.palaeo.2025.112780","url":null,"abstract":"<div><div>Magnetostratigraphic dating is an important method for establishing the chronological framework of Chinese loess. However, the positions of geomagnetic polarity boundaries and anomalous geomagnetic excursions have been reported inconsistently across different loess sections. Previous studies have questioned the fidelity of the primary remanent magnetization recorded by coarse loess layers, as it may be influenced by remagnetization processes during subsequent geomagnetic reversals. In this study, we simulated magnetic field reversals in the laboratory to investigate their effect on paleomagnetic records in Middle and Late Pleistocene loess and paleosol samples from the western and southeastern Chinese Loess Plateau (CLP). The results reveal that: 1) Remagnetization processes are more likely to occur in surface subsamples from the same block of loess compared to interior subsamples, while such phenomena are rare in paleosol samples. 2) Individual specimens from the western CLP are more prone to exhibiting anomalous remanent magnetization components, suggesting that coarser and more porous samples are more susceptible to recording erratic paleomagnetic information. 3) Secondary remanent magnetization acquired in the laboratory is unstable and exhibits varied thermal demagnetization behaviors among individual subsamples. These observations suggest that the reliability of short geomagnetic reversals, as well as the transition processes and behaviors recorded in Chinese loess, should be carefully re-evaluated. The effects of remagnetization cannot be ignored when investigating the magnetostratigraphy of Chinese loess.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"662 ","pages":"Article 112780"},"PeriodicalIF":2.6,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143147545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Pearl River delta (PRD) is situated on the southeastern coast of the Chinese mainland, facing the northern part of the South China Sea. Its estuary serves as the main sedimentary region for river discharge. The Quaternary sedimentary units consist primarily of two major sets of transgressive and regressive sequences. However, controversy exists regarding the chronology of the late Pleistocene marine transgression sequence. High-resolution records for the paleovegetation and paleoclimate of the late Quaternary upper and lower marine cycles are also lacking. In this study, a detailed analysis involving pollen, microfossils, and particle size has been carried out on a core from the Macau Sea area in the southwest of the Pearl River estuary. Chronostratigraphic models were based on accelerator mass spectrometry (AMS) 14C and optically stimulated luminescence (OSL) dating, combined with regional stratigraphic correlations. The reconstructed sediment facies for the late Pleistocene were mainly tidal flat, delta front, and pro-delta, corresponding to Marine Isotope Stage 5 (MIS5). The finding of mangrove Sonneratia pollen along with numerous tropical rain forest elements in the late Pleistocene sediments not only indicates a mud tidal flat environment in the PRD, but also reflects tropical climatic conditions. By comparing the pollen assemblages from the MIS5 and early part of the Holocene period (9.2–7.5 cal kyr BP) statistically, we obtained a consistent assemblage dominated by the same pollen taxa favoring warm and humid tropical conditions, which further confirmed the late (i.e. MIS5) age for the Pleistocene sequence. For the topmost samples representing the last 900 years, high percentages of Poaceae, Artemisia, Cyperaceae and fern spores, significantly different from those observed in samples from the early to mid-Holocene as well as the MIS5 interglacial sediments, indicated a strong anthropogenic impact on land cover.
{"title":"The vegetation response to MIS5 and MIS1 as revealed by pollen data from the Pearl River estuary, China","authors":"Shaohua Yu , Fang Chen , Kangyou Huang , Yang Zhou , Qing Zhu , Cong Wu , Chang Zhuang , Kaijun Cao , Lu Yamin , Jinpeng Zhang , Zhuo Zheng","doi":"10.1016/j.palaeo.2025.112774","DOIUrl":"10.1016/j.palaeo.2025.112774","url":null,"abstract":"<div><div>The Pearl River delta (PRD) is situated on the southeastern coast of the Chinese mainland, facing the northern part of the South China Sea. Its estuary serves as the main sedimentary region for river discharge. The Quaternary sedimentary units consist primarily of two major sets of transgressive and regressive sequences. However, controversy exists regarding the chronology of the late Pleistocene marine transgression sequence. High-resolution records for the paleovegetation and paleoclimate of the late Quaternary upper and lower marine cycles are also lacking. In this study, a detailed analysis involving pollen, microfossils, and particle size has been carried out on a core from the Macau Sea area in the southwest of the Pearl River estuary. Chronostratigraphic models were based on accelerator mass spectrometry (AMS) <sup>14</sup>C and optically stimulated luminescence (OSL) dating, combined with regional stratigraphic correlations. The reconstructed sediment facies for the late Pleistocene were mainly tidal flat, delta front, and pro-delta, corresponding to Marine Isotope Stage 5 (MIS5). The finding of mangrove <em>Sonneratia</em> pollen along with numerous tropical rain forest elements in the late Pleistocene sediments not only indicates a mud tidal flat environment in the PRD, but also reflects tropical climatic conditions. By comparing the pollen assemblages from the MIS5 and early part of the Holocene period (9.2–7.5 cal kyr BP) statistically, we obtained a consistent assemblage dominated by the same pollen taxa favoring warm and humid tropical conditions, which further confirmed the late (i.e. MIS5) age for the Pleistocene sequence. For the topmost samples representing the last 900 years, high percentages of Poaceae, <em>Artemisia</em>, Cyperaceae and fern spores, significantly different from those observed in samples from the early to mid-Holocene as well as the MIS5 interglacial sediments, indicated a strong anthropogenic impact on land cover.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"662 ","pages":"Article 112774"},"PeriodicalIF":2.6,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-28DOI: 10.1016/j.palaeo.2025.112776
Ruxi Dou , Jianjun Zou , Zhi Dong , Xuefa Shi , Yonghua Wu , Aimei Zhu , Xuguang Feng , Xinqing Zou , Sergey A. Gorbarenko , Yuriy P. Vasilenko , Aleksandr A. Bosin
The Sea of Japan (JS) is characterized by hydrodynamics that are highly sensitive to climate change. Current knowledge of JS hydrodynamics over geological timescales stems mainly from studies of sediment lithology, biomarkers and microfossils. However, the relationship between sedimentological proxies, such as Sortable Silt (SS), and hydrodynamics remains poorly understood. Here we analyzed SS parameters and elemental ratios from sediment cores collected at three distinct locations (southwestern, central, and northwestern JS) to investigate hydrodynamic changes during the last glaciation. Our results suggest hydrodynamics intensified in the southwestern JS around 18 ka, coinciding with the initial intrusion of the Tsushima Warm Current (TWC). Enhanced hydrodynamics occurred in the central JS around 16 ka, driven by sustained TWC's intrusion and northward shift of the subpolar front (SPF). Accompanied the northern shift of SPF, the convergence of northern cold and southern warm waters around the SPF caused surface water densification and sinking in the central JS, enhancing local hydrodynamics and sediment sorting at that time. In the northwestern JS, hydrodynamics is primarily influenced by brine rejection process induced by sea-ice activity. Our records show the TWC and sea-ice activity primarily drove site-specific hydrodynamics changes in the JS during the last deglaciation, providing valuable insights into JS paleoceanography from a hydrodynamic perspective.
{"title":"The impacts of Tsushima Warm Current and sea-ice on hydrodynamics in the Sea of Japan during the last deglaciation","authors":"Ruxi Dou , Jianjun Zou , Zhi Dong , Xuefa Shi , Yonghua Wu , Aimei Zhu , Xuguang Feng , Xinqing Zou , Sergey A. Gorbarenko , Yuriy P. Vasilenko , Aleksandr A. Bosin","doi":"10.1016/j.palaeo.2025.112776","DOIUrl":"10.1016/j.palaeo.2025.112776","url":null,"abstract":"<div><div>The Sea of Japan (JS) is characterized by hydrodynamics that are highly sensitive to climate change. Current knowledge of JS hydrodynamics over geological timescales stems mainly from studies of sediment lithology, biomarkers and microfossils. However, the relationship between sedimentological proxies, such as Sortable Silt (SS), and hydrodynamics remains poorly understood. Here we analyzed SS parameters and elemental ratios from sediment cores collected at three distinct locations (southwestern, central, and northwestern JS) to investigate hydrodynamic changes during the last glaciation. Our results suggest hydrodynamics intensified in the southwestern JS around 18 ka, coinciding with the initial intrusion of the Tsushima Warm Current (TWC). Enhanced hydrodynamics occurred in the central JS around 16 ka, driven by sustained TWC's intrusion and northward shift of the subpolar front (SPF). Accompanied the northern shift of SPF, the convergence of northern cold and southern warm waters around the SPF caused surface water densification and sinking in the central JS, enhancing local hydrodynamics and sediment sorting at that time. In the northwestern JS, hydrodynamics is primarily influenced by brine rejection process induced by sea-ice activity. Our records show the TWC and sea-ice activity primarily drove site-specific hydrodynamics changes in the JS during the last deglaciation, providing valuable insights into JS paleoceanography from a hydrodynamic perspective.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"662 ","pages":"Article 112776"},"PeriodicalIF":2.6,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143147553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-28DOI: 10.1016/j.palaeo.2025.112782
Zhigang Zhang , Dan Zhao , Chaogang Zheng , Jian Wang , Jiahong Zheng , Haitao Cui , Zhijun Zhao , Xinggong Kong , Xiaobin Xu , Zhiyang Chang , Yiman Li
Quaternary climate change on the Tibetan Plateau is vital for understanding environmental evolution both globally and in the Northern Hemisphere. The Paleo-Daocheng Ice Cap (PDIC), located on the southeastern Tibetan Plateau (TP), plays a crucial role in exploring the coupling mechanism between TP uplift and climate change. This study sampled granules, pebbles, boulders, and coarse-grained sand from the surfaces of moraines and bedrock samples in the PDIC area. The new 10Be exposure ages of 23 samples from three different glacial remnants of the PDIC ranged from 71.0 ± 4.6 to 15.6 ± 1.0 ka. Subsequently, a comprehensive analysis of both new and previously-compiled 10Be ages from the Shaluli Mountains was conducted. This analysis confirmed that the area entered the cryosphere around 0.8–0.6 Ma. Probabilistic cosmogenic age analysis tool (P-CAAT) analysis on the 10Be ages since Marine Isotope Stage (MIS) 6 was also conducted. This identified at least four significant glacial fluctuations (at 153.5 ± 17.6 ka, 109.7 ± 18.6 ka, 54.0 ± 14.4 ka, and 19.4 ± 9.2 ka). These glacial fluctuations represent a comprehensive response to temperature, precipitation, and insolation, with these climate determinants making varying contributions across different stages since MIS 6.
{"title":"Quaternary glacial history of the Paleo-Daocheng ice cap (southeast Tibetan Plateau) reconstructed from in situ cosmogenic 10Be ages","authors":"Zhigang Zhang , Dan Zhao , Chaogang Zheng , Jian Wang , Jiahong Zheng , Haitao Cui , Zhijun Zhao , Xinggong Kong , Xiaobin Xu , Zhiyang Chang , Yiman Li","doi":"10.1016/j.palaeo.2025.112782","DOIUrl":"10.1016/j.palaeo.2025.112782","url":null,"abstract":"<div><div>Quaternary climate change on the Tibetan Plateau is vital for understanding environmental evolution both globally and in the Northern Hemisphere. The Paleo-Daocheng Ice Cap (PDIC), located on the southeastern Tibetan Plateau (TP), plays a crucial role in exploring the coupling mechanism between TP uplift and climate change. This study sampled granules, pebbles, boulders, and coarse-grained sand from the surfaces of moraines and bedrock samples in the PDIC area. The new <sup>10</sup>Be exposure ages of 23 samples from three different glacial remnants of the PDIC ranged from 71.0 ± 4.6 to 15.6 ± 1.0 ka. Subsequently, a comprehensive analysis of both new and previously-compiled <sup>10</sup>Be ages from the Shaluli Mountains was conducted. This analysis confirmed that the area entered the cryosphere around 0.8–0.6 Ma. Probabilistic cosmogenic age analysis tool (P-CAAT) analysis on the <sup>10</sup>Be ages since Marine Isotope Stage (MIS) 6 was also conducted. This identified at least four significant glacial fluctuations (at 153.5 ± 17.6 ka, 109.7 ± 18.6 ka, 54.0 ± 14.4 ka, and 19.4 ± 9.2 ka). These glacial fluctuations represent a comprehensive response to temperature, precipitation, and insolation, with these climate determinants making varying contributions across different stages since MIS 6.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"663 ","pages":"Article 112782"},"PeriodicalIF":2.6,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143312212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-27DOI: 10.1016/j.palaeo.2025.112763
Jonathan E. Bellinzoni , Luciano O. Valenzuela , José L. Prado
The extinction of megamammals during the Late Pleistocene in South America remains a topic of considerable debate, particularly regarding the influence of human activity. This study employs stable isotope analysis (δ13C and δ18O) to investigate the paleoecology of two extinct horse species, Equus neogeus and Hippidion principale, from the Argentine Pampas. Our findings reveal consistent temporal trends in the horses' isotopic values across both Pleistocene and Marine Isotope Stages (MIS) of the last glacial (MIS 1–2) and interglacial (MIS 5–6) period, with notable differences emerging in the Late Pleistocene. While both species maintained similar feeding habits for much of the Pleistocene, Equus neogeus exhibited greater δ13C variability in the Late Pleistocene, indicating dietary flexibility and a shift towards C4 vegetation. In contrast, Hippidion principale maintained a more stable diet. These results suggest that Equus adapted to changing vegetation driven by climatic fluctuations, while Hippidion may have been more vulnerable to environmental changes and human presence, potentially contributing to its extinction. We expanded the spatial and temporal scope of horse isotope data by incorporating previously unstudied localities and underrepresented periods, providing new isotopic values for both species. Our study offers fresh insights into the complex interplay between climate, human activity, and megafaunal extinctions in the Argentine Pampas.
{"title":"Isotopic evidence of dietary strategies and taxa-specific adaptive responses in the extinction of Pleistocene equids from the argentine Pampas","authors":"Jonathan E. Bellinzoni , Luciano O. Valenzuela , José L. Prado","doi":"10.1016/j.palaeo.2025.112763","DOIUrl":"10.1016/j.palaeo.2025.112763","url":null,"abstract":"<div><div>The extinction of megamammals during the Late Pleistocene in South America remains a topic of considerable debate, particularly regarding the influence of human activity. This study employs stable isotope analysis (<em>δ</em><sup>13</sup>C and <em>δ</em><sup>18</sup>O) to investigate the paleoecology of two extinct horse species, <em>Equus neogeus</em> and <em>Hippidion principale</em>, from the Argentine Pampas. Our findings reveal consistent temporal trends in the horses' isotopic values across both Pleistocene and Marine Isotope Stages (MIS) of the last glacial (MIS 1–2) and interglacial (MIS 5–6) period, with notable differences emerging in the Late Pleistocene. While both species maintained similar feeding habits for much of the Pleistocene, <em>Equus neogeus</em> exhibited greater <em>δ</em><sup>13</sup>C variability in the Late Pleistocene, indicating dietary flexibility and a shift towards C<sub>4</sub> vegetation. In contrast, <em>Hippidion principale</em> maintained a more stable diet. These results suggest that <em>Equus</em> adapted to changing vegetation driven by climatic fluctuations, while <em>Hippidion</em> may have been more vulnerable to environmental changes and human presence, potentially contributing to its extinction. We expanded the spatial and temporal scope of horse isotope data by incorporating previously unstudied localities and underrepresented periods, providing new isotopic values for both species. Our study offers fresh insights into the complex interplay between climate, human activity, and megafaunal extinctions in the Argentine Pampas.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"662 ","pages":"Article 112763"},"PeriodicalIF":2.6,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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