The continental expression of global cooling during the Miocene Climate Transition in Central Asia is poorly documented, as the tectonically active setting complicates the correlation of Neogene regional and global climatic developments. This study presents new geochemical data (CaSO 4 content, carbonate δ 13 C and δ 18 O) from the endorheic alluvial-lacustrine Aktau succession (Ili Basin, southeast Kazakhstan) combined with findings from the previously published facies evolution. Time series analysis revealed long-eccentricity forcing of the paleohydrology throughout the entire succession, split into several facies-dependent segments. Orbital tuning, constrained by new laser ablation U-Pb dates and a preexisting magnetostratigraphy, places the succession in a 5.0 Ma long interval in the middle to late Miocene (15.6 to 10.6 Ma). The long-term water accumulation in the Ili Basin followed the timing of the Miocene Climate Transition, suggesting increased precipitation in the catchment area in response to climate cooling and stronger westerly winds. This was paced by minima of the 2.4 Ma eccentricity cycle, which favored the establishment of a discharge playa (~14.3 Ma) and a perennial lake (12.6 to 11.8 Ma). Furthermore, low obliquity amplitudes (nodes) caused a transient weakening of the westerlies at~13.7 to 13.5 Ma and at~12.7 Ma, resulting in negative hydrological budgets and salinization. Flooding of the windward Ili Basin coeval with aridification in the leeward basins suggests that the Tian Shan was a climate boundary already in the middle Miocene. Our results emphasize the impact of climate fluctuations on the westerlies' strength and thus on Central Asian hydrology. Plain Language Summary The global climate changed from an exceptional warm to a colder state in the middle Miocene epoch, representing a milestone in the evolution of today's climate. This study focuses on the, so far fragmentary, understanding of the Central Asian climate response to this global climate transition by investigating deposits of a former (salt) lake in the Ili Basin, southeast Kazakhstan. Regular sediment alternations represent cycles of low and high water level, overprinted by a long-term lake expansion. Time series analysis of climate sensitive geochemical and environmental parameters, together with the determination of absolute rock ages, enabled the identification of sedimentary cycles (405 ka and 1.2 Ma long), which are equivalent to climate influencing variations of the Earth's orbit and tilt angle. We conclude that water level maxima are linked to periods of low seasonal climate differences reoccurring every 405 ka. The lake expansion is caused by more precipitation due to strengthened westerly winds, in response to global cooling. Westerly winds were transiently weakened during periods of low variability of the Earth's tilt angle, promoting high evaporation and salinization. Our results emphasize the impact of climate change on the westerlies' strength and thus on Central Asian moisture supply.

The modern precipitation balance in southeastern (SE) Brazil is regulated by the South American summer Monsoon and threatened by global climate change. On glacial-interglacial timescales, monsoon intensity was strongly controlled by precession-forced changes in insolation. To date, relatively little is known about the spatiotemporal distribution of tropical precipitation in SE Brazil and the resulting variability of fluvial discharge on glacial-interglacial timescales. Here, we present X-ray diffraction-derived mineralogical data for the 150–70 ka period (marine isotope stage (MIS) 6 to MIS 5) from the Doce River basin. This area was sensitive to changes in monsoonal precipitation intensity due to its proximity to the South Atlantic Convergence Zone. The data, obtained from a marine sediment core (M125-55–7) close to the Doce river mouth (20°S), show pronounced changes in the Doce River suspension load’s mineralogical composition on glacial-interglacial and precessional timescales. While the ratio of silicates to carbonates displays precession-paced changes, the mineralogical composition of the carbonate-free fraction discriminates between two assemblages which strongly vary between glacial and interglacial time scales, with precession-forced variability only visible in MIS 5. The first assemblage, dominated by high contents of kaolinite and gibbsite, indicates intensified lowland erosion of mature tropical soils. The second one, characterized by higher contents of the well-ordered illite, quartz and albite, points to intensified erosion of immature soils in the upper Doce Basin. High kaolinite contents in the silicate fraction prevailed in late MIS 6 and indicate pronounced lowland soil erosion along a steepened topographic gradient. The illite-rich mineral assemblage was more abundant in MIS 5, particularly during times of high austral summer insolation, indicating strong monsoonal rainfall and intense physical erosion in the upper catchment. When the summer monsoon weakened in times of lower insolation, the mineral assemblage was dominated by kaolinite again, indicative of lower precipitation and runoff in the upper catchment and dominant lowland erosion.

<p>The present-day hydrological cycle in southeastern Brazil depends on the intensity of the South American Summer Monsoon (SASM) with strong monsoonal precipitation during austral summer (DJF) and weak precipitation during austral winter (JJA). On glacial-interglacial timescales, monsoonal intensity was mainly controlled by precession-forced changes in insolation.</p><p>Relatively little is known to date about the spatial distribution of precipitation in the hinterland and coastal areas of SE Brazil and the resulting variability of the fluvial discharge on glacial-interglacial timescales. The Doce River basin is situated at the northern boundary of the present-day South Atlantic Convergence Zone (SACZ), wherefore its run-off and suspension load respond sensitive to changes in both summer monsoon and coastal winter precipitation. The soil and rock distribution of the basin allows for the study of the relative proportions of terrigenous up- and lowland sources among the transported fluvial sediments.</p><p>We studied the mineralogical composition and crystallinity of the non-carbonate fine fraction from late Marine Isotope Stage (MIS) 6 to MIS 5 (150-70 ka) in a marine sediment core obtained in the proximity of the Doce river mouth (20° S, 38° W, 2 km water depth). The main non-carbonate mineral content comprises quartz, albite, illite, kaolinite and gibbsite. The relative abundances of the mineral assemblage show distinct changes relative to changes in summer insolation as well as across the MIS 6-5 transition. Thereby, the mineral assemblage shows a distinct end-member pattern, with high contents of illite (80 % 2M-polytype) and high illite crystallinity as a proxy for stronger physical erosion of the parent rocks in the steep upland, and high contents of kaolinite and gibbsite as proxy for intense tropical soil erosion in the lowlands.</p><p>During MIS 5, the insolation dependent cyclicity seen in the mineral assemblage shows high illite/kaolinite ratios when austral summer insolation is high and low illite/kaolinite ratios in low insolation phases. This pattern is not visible in late MIS 6, when very low illite/kaolinite ratios are present during high austral summer insolation.</p><p>We consider the spatial changes in erosion intensity to be caused by variations in the regional precipitation pattern. Thereby, pronounced upland erosion is caused by severe precipitation and discharge events during a strong SASM. A relatively increased lowland erosion indicates both increased austral winter precipitation due to stronger trade wind forcing and a weaker monsoonal system in the upper discharge area. The lack of a strong insolation-control on illite/kaolinite ratios during MIS 6 is interpreted as an overall weakening of the SASM system during glacial periods, when austral winter precipitation exerted a stronger control on the hydrological budget of the Doce River.</p>