Jiaoyang Ruan

Alpine glacier histories beyond the Last Glacial Maximum are poorly resolved, impeding our ability to test how mountain glaciers respond to dynamic forcings on orbital to sub‑orbital timescales. This gap may be addressed through proxy records from alpine caves, in which subglacial speleothem growth is facilitated by recharge beneath temperate glaciers through sulphide-bearing epikarst. However, the use of conventional stable isotopes of carbon (δ¹³C) and oxygen (δ¹⁸O) in speleothem calcite yields ambiguities when interpreting environmental transitions and ice cover during glacial inception and retreat. Herein, we present a multiproxy speleothem record from Betten Cave (Melchsee Frutt, central Swiss Alps) spanning 415–360 ka that integrates sulphate stable isotopes (δ³⁴S_SO4, δ¹⁸O_SO4) and trace‑element geochemistry with calcite δ¹³C–δ¹⁸O to diagnose redox state, sulphide‑oxidation pathways, and hydrological reorganization across the Marine Isotope Stage 11/10 glacial inception. Three environmental phases are identified from this dataset, marking the transition from (1) a vegetated and soil-covered montane valley to (2) a soil-limited periglacial setting, hydrologically influenced by glacier advance through the adjacent valley (~2,000 m a.s.l.), to (3) subglacial speleothem growth, in which a temperature glacier covered the lowest elevation of the cave system (~1,700 m a.s.l.). After 402 ± 4 ka, a long-term decrease in the isotopic offset between water and aqueous sulphate (Δδ¹⁸O_SO4−H2O) records progressive oxygen limitation concomitant with glacier thickening and advance over the cave site by 372 ± 3 ka. Coeval peaks in cations and redox‑sensitive transition metals reflect the enhanced delivery of glacially comminuted detritus and coupled Fe–Mn redox cycling within the subglacial karst system. These results directly link sulphate oxygen- and sulphur-isotope systematics and trace‑element fingerprints to glacier dynamics, providing geochronologically precise benchmarks and a transferable framework for reconstructing mountain glacier behaviour where geomorphic records are incomplete.

Alpine glacier histories beyond the Last Glacial Maximum are poorly resolved, impeding our ability to test how mountain glaciers respond to dynamic forcings on orbital to sub‑orbital timescales. This gap may be addressed through proxy records from alpine caves, in which subglacial speleothem growth is facilitated by recharge beneath temperate glaciers through sulphide-bearing epikarst. However, the use of conventional stable isotopes of carbon (δ¹³C) and oxygen (δ¹⁸O) in speleothem calcite yields ambiguities when interpreting environmental transitions and ice cover during glacial inception and retreat. Herein, we present a multiproxy speleothem record from Betten Cave (Melchsee Frutt, central Swiss Alps) spanning 415–360 ka that integrates sulphate stable isotopes (δ³⁴S_SO4, δ¹⁸O_SO4) and trace‑element geochemistry with calcite δ¹³C–δ¹⁸O to diagnose redox state, sulphide‑oxidation pathways, and hydrological reorganization across the Marine Isotope Stage 11/10 glacial inception. Three environmental phases are identified from this dataset, marking the transition from (1) a vegetated and soil-covered montane valley to (2) a soil-limited periglacial setting, hydrologically influenced by glacier advance through the adjacent valley (~2,000 m a.s.l.), to (3) subglacial speleothem growth, in which a temperature glacier covered the lowest elevation of the cave system (~1,700 m a.s.l.). After 402 ± 4 ka, a long-term decrease in the isotopic offset between water and aqueous sulphate (Δδ¹⁸O_SO4−H2O) records progressive oxygen limitation concomitant with glacier thickening and advance over the cave site by 372 ± 3 ka. Coeval peaks in cations and redox‑sensitive transition metals reflect the enhanced delivery of glacially comminuted detritus and coupled Fe–Mn redox cycling within the subglacial karst system. These results directly link sulphate oxygen- and sulphur-isotope systematics and trace‑element fingerprints to glacier dynamics, providing geochronologically precise benchmarks and a transferable framework for reconstructing mountain glacier behaviour where geomorphic records are incomplete.

The woolly rhinoceros was a prominent Ice Age megafaunal species, and there is limited knowledge regarding its origin and responses to past glacial cycles. We sequenced 29 mitochondrial and 14 nuclear genomes from Pleistocene specimens across Eurasia and modeled the species’ habitats over the past 500,000 years. Our results suggest that its maternal genetic diversity mainly evolved in temperate Eurasia around 460 thousand to 420 thousand years ago during a prolonged glacial-interglacial transition. We found that a ~170-thousand-year-old East Asian individual was ancestral to all later populations, indicating East Asia as one possible origin of Late Pleistocene ancestry. We also identified the Altai region as a major climatic refugium. These findings highlight the crucial role of temperate Eurasia in the evolution of woolly rhinoceroses and the diversification of cold-adapted megafauna.

Late Pleistocene climate in the European Alps was marked by large, orbitally driven fluctuations in temperature, precipitation, and ice extent. Reconstructing mountain glaciation prior to the Last Glacial Maximum remains challenging, however, because glacial deposits are often eroded or reworked. Here we present a 90-kyr speleothem record from Klaus Cramer Cave (western Austria) spanning Marine Isotope Stages (MIS) 12–10. Stable-isotope and trace-element data identify intervals of subglacial speleothem growth associated with warm-based ice cover. Subglacial phases are characterized by low δ ¹⁸ O, high δ ¹³ C, and highly elevated sulfur concentrations, indicating enhanced sulfide oxidation from the infiltration of meltwater through glacially comminuted detritus. Sulfate δ ³⁴ S and δ ¹⁸ O values signal that the aerobic oxidation of pyrite was the dominant sulfur source. In the absence of geomorphological evidence, we constrain the timing of warm-based ice retreat to 423.3 ± 1.6 ka and re-advance to 370.8 ^+2.1 / _−1.8 ka, while MIS 11 remained entirely ice-free.

Alpine glacier histories beyond the Last Glacial Maximum are poorly resolved, impeding our ability to test how mountain glaciers respond to dynamic forcings on orbital to sub‑orbital timescales. This gap may be addressed through proxy records from alpine caves, in which subglacial speleothem growth is facilitated by recharge beneath temperate glaciers through sulphide-bearing epikarst. However, the use of conventional stable isotopes of carbon (δ¹³C) and oxygen (δ¹⁸O) in speleothem calcite yields ambiguities when interpreting environmental transitions and ice cover during glacial inception and retreat. Herein, we present a multiproxy speleothem record from Betten Cave (Melchsee Frutt, central Swiss Alps) spanning 415–360 ka that integrates sulphate stable isotopes (δ³⁴S_SO4, δ¹⁸O_SO4) and trace‑element geochemistry with calcite δ¹³C–δ¹⁸O to diagnose redox state, sulphide‑oxidation pathways, and hydrological reorganization across the Marine Isotope Stage 11/10 glacial inception. Three environmental phases are identified from this dataset, marking the transition from (1) a vegetated and soil-covered montane valley to (2) a soil-limited periglacial setting, hydrologically influenced by glacier advance through the adjacent valley (~2,000 m a.s.l.), to (3) subglacial speleothem growth, in which a temperature glacier covered the lowest elevation of the cave system (~1,700 m a.s.l.). After 402 ± 4 ka, a long-term decrease in the isotopic offset between water and aqueous sulphate (Δδ¹⁸O_SO4−H2O) records progressive oxygen limitation concomitant with glacier thickening and advance over the cave site by 372 ± 3 ka. Coeval peaks in cations and redox‑sensitive transition metals reflect the enhanced delivery of glacially comminuted detritus and coupled Fe–Mn redox cycling within the subglacial karst system. These results directly link sulphate oxygen- and sulphur-isotope systematics and trace‑element fingerprints to glacier dynamics, providing geochronologically precise benchmarks and a transferable framework for reconstructing mountain glacier behaviour where geomorphic records are incomplete.

Alpine glacier histories beyond the Last Glacial Maximum are poorly resolved, impeding our ability to test how mountain glaciers respond to dynamic forcings on orbital to sub‑orbital timescales. This gap may be addressed through proxy records from alpine caves, in which subglacial speleothem growth is facilitated by recharge beneath temperate glaciers through sulphide-bearing epikarst. However, the use of conventional stable isotopes of carbon (δ¹³C) and oxygen (δ¹⁸O) in speleothem calcite yields ambiguities when interpreting environmental transitions and ice cover during glacial inception and retreat. Herein, we present a multiproxy speleothem record from Betten Cave (Melchsee Frutt, central Swiss Alps) spanning 415–360 ka that integrates sulphate stable isotopes (δ³⁴S_SO4, δ¹⁸O_SO4) and trace‑element geochemistry with calcite δ¹³C–δ¹⁸O to diagnose redox state, sulphide‑oxidation pathways, and hydrological reorganization across the Marine Isotope Stage 11/10 glacial inception. Three environmental phases are identified from this dataset, marking the transition from (1) a vegetated and soil-covered montane valley to (2) a soil-limited periglacial setting, hydrologically influenced by glacier advance through the adjacent valley (~2,000 m a.s.l.), to (3) subglacial speleothem growth, in which a temperature glacier covered the lowest elevation of the cave system (~1,700 m a.s.l.). After 402 ± 4 ka, a long-term decrease in the isotopic offset between water and aqueous sulphate (Δδ¹⁸O_SO4−H2O) records progressive oxygen limitation concomitant with glacier thickening and advance over the cave site by 372 ± 3 ka. Coeval peaks in cations and redox‑sensitive transition metals reflect the enhanced delivery of glacially comminuted detritus and coupled Fe–Mn redox cycling within the subglacial karst system. These results directly link sulphate oxygen- and sulphur-isotope systematics and trace‑element fingerprints to glacier dynamics, providing geochronologically precise benchmarks and a transferable framework for reconstructing mountain glacier behaviour where geomorphic records are incomplete.

Alpine glacier histories beyond the Last Glacial Maximum are poorly resolved, impeding our ability to test how mountain glaciers respond to dynamic forcings on orbital to sub‑orbital timescales. This gap may be addressed through proxy records from alpine caves, in which subglacial speleothem growth is facilitated by recharge beneath temperate glaciers through sulphide-bearing epikarst. However, the use of conventional stable isotopes of carbon (δ13C) and oxygen (δ18O) in speleothem calcite yields ambiguities when interpreting environmental transitions and ice cover during glacial inception and retreat. Herein, we present a multiproxy speleothem record from Betten Cave (Melchsee Frutt, central Swiss Alps) spanning 415–360 ka that integrates sulphate stable isotopes (δ34SSO4, δ18OSO4) and trace‑element geochemistry with calcite δ13C–δ18O to diagnose redox state, sulphide‑oxidation pathways, and hydrological reorganization across the Marine Isotope Stage 11/10 glacial inception. Three environmental phases are identified from this dataset, marking the transition from (1) a vegetated and soil-covered montane valley to (2) a soil-limited periglacial setting, hydrologically influenced by glacier advance through the adjacent valley (~2,000 m a.s.l.), to (3) subglacial speleothem growth, in which a temperature glacier covered the lowest elevation of the cave system (~1,700 m a.s.l.). After 402 ± 4 ka, a long-term decrease in the isotopic offset between water and aqueous sulphate (Δδ18OSO4−H2O) records progressive oxygen limitation concomitant with glacier thickening and advance over the cave site by 372 ± 3 ka. Coeval peaks in cations and redox‑sensitive transition metals reflect the enhanced delivery of glacially comminuted detritus and coupled Fe–Mn redox cycling within the subglacial karst system. These results directly link sulphate oxygen- and sulphur-isotope systematics and trace‑element fingerprints to glacier dynamics, providing geochronologically precise benchmarks and a transferable framework for reconstructing mountain glacier behaviour where geomorphic records are incomplete.

Millet agriculture was foundational to the emergence of complex societies in Neolithic East Asia, yet the environmental mechanisms shaping its spatiotemporal development remain unresolved. Here, we present a high-resolution reconstruction of Holocene growing-season soil temperature from biomarker proxies in a precisely dated loess sequence from the central Chinese Loess Plateau. Our data reveal a pronounced ~3 °C soil cooling between ~7.5 to 6.0 thousand years B.P. (kyr B.P.), followed by rapid warming and millennia-long relatively stable conditions. By integrating archaeological datasets with transient climate simulations, we show that this mid-Holocene soil cooling which reflects coupled climatic forcing and vegetation-related land surface changes likely compressed the thermally suitable niche for frost-sensitive millets, contributing to a southward displacement of cultivation and delaying large-scale agricultural expansion until the subsequent soil temperature recovery after ~6.0 kyr B.P. These findings suggest that large-amplitude soil temperature fluctuations acted as a modulating climatic constraint on the geographic distribution and development trajectory of millet agriculture in East Asia, providing refined insights into climate–society interactions during the Neolithic.

Caractérisation de la variabilité du climat holocène à l’ouest de l’Europe et du bassin de la Méditerranée à partir de l’étude haute résolution de spéléothèmes: Déchiffrer le climat de l’Holocène est la base d’une meilleure compréhension du climat moderne. En effet, à cette époque le climat en Europe est très complexe est montre de fortes variations spatiales et il reste beaucoup à faire pour améliorer la couverture géographique d’enregistrements bien datés et de haute résolution. En tant qu’archives paléoclimatiques, les spéléothèmes ont de larges avantages concernant leur chronologie et leur résolution temporelle et peuvent aider à combler cette lacune. Dans cette thèse, des stalagmites holocènes ont été sélectionnées selon un transect N-S entre les latitudes 35° et 65°N à l’ouest de l’Europe et du bassin méditerranéen (de la Suède à l’Algérie). Elles ont été datées densément par U-Th et échantillonnées à haute résolution pour analyser leur composition isotopique et géochimique. Le climat de l’Holocène a été déduit des analyses isotopiques de la calcite (δ¹³C, δ¹⁸O) et du rapport Mg/Ca. Combinées avec les données existantes et avec les simulations numériques des modèles, ces nouvelles données ont permis d’émettre des hypothèses sur les processus dynamiques contrôlant les changement climatiques régionaux comme les divers modes impliqués dans la circulation océanique et atmosphérique. Sur un site archéologique particulier, le lien climat/activités humaines a aussi pu être étudié. Les principaux résultats de cette thèse sont : 1) les enregistrements en δ¹⁸O, δ¹³C et Mg/Ca d’une stalagmite de la grotte de Villars (sud-ouest de la France), ont révélé une variabilité décennale à multimillénaire du climat au cours des derniers 14200 ans ainsi que les preuves d’une déforestation il y a environ 1000 ans ; 2) deux stalagmites provenant de la grotte de Villars au sud-ouest de la France et de la grotte Korallgrottan au nord-ouest de la Suède ont enregistré de façon remarquable l’événement climatique du 8.2 ka et les différentes étapes qui le composent montrant des différences régionales de température et d’humidité entre les deux sites. Celles-ci sont associées avec une interruption suivie d’une réorganisation de la circulation océanique et atmosphérique ; 3) les enregistrements en δ¹⁸O et en δ¹³C de deux stalagmites de la grotte de Villars suggèrent aussi l’existence d’une période humide multi-centennale il y a ~7200-7600 liée éventuellement à la fonte de la dernière portion de la calotte de la Laurentide ; 4) les isotopes stables (δ¹⁸O, δ¹³C) d’une stalagmite de la grotte du Père-Noël située au sud-est de la Belgique, révèle de larges variations hydro climatiques entre 10500 et 4200 ans. En particulier, une période sèche multi-centennale est mise en évidence il y a ~5600-6000 ans probablement liée à un changement des vents d’ouest ; 5) au nord de l’Algérie, dans la grotte de Gueldaman, plusieurs stalagmites ont montré, par leur δ¹³C et leur δ¹⁸O, l’impact d’une période sèche sur l’occupation humaine et finalement l’abandon du site par les hommes préhistoriques il y a ~4200 ans.