Astronomical forcing of lake evolution in the Lanzhou Basin during early Miocene period

Eccentricity-paced monsoon variability on the northeastern Tibetan Plateau in the Late Oligocene high CO 2 world

“…2 ). The Rb/Sr record of Early Miocene red mudstones and sandstones in the Lanzhou Basin has been suggested to be sensitive to subtle pedogenic weathering variability ( 20 ), despite the prevailing low precipitation and weathering intensity. In general, higher precipitation causes stronger pedogenic weathering of the red mudstone, which depletes mobile Sr and enriches insoluble Rb, leading to higher Rb/Sr values ( 20 ).…”

“…The Rb/Sr record of Early Miocene red mudstones and sandstones in the Lanzhou Basin has been suggested to be sensitive to subtle pedogenic weathering variability ( 20 ), despite the prevailing low precipitation and weathering intensity. In general, higher precipitation causes stronger pedogenic weathering of the red mudstone, which depletes mobile Sr and enriches insoluble Rb, leading to higher Rb/Sr values ( 20 ). In addition to local magnetic mineral formation during pedogenic weathering, higher precipitation and associated stronger stream flow dynamics increases erosion and facilitates more magnetic materials to be eroded and transported from the surrounding mountains and catchment area to the deposition site.…”

“…1, B and C ), spans a (near-) continuous time interval between 28.1 and 24.1 Ma BP ( 15 , 16 , 18 , 19 ). Here, we use elemental and environmental magnetic records from this terrestrial sequence, which are related to regional hydroclimate fluctuations in the Lanzhou Basin ( 20 , 21 ), to provide insight to orbital variability and dynamics of monsoon precipitation on the NE Tibetan Plateau margin in the Late Oligocene high CO 2 world. Our results represent the first ~4-thousand year (ka) resolution Late Oligocene monsoon records from the Tibetan Plateau and thereby help fill a gap in our understanding of the orbital Asian monsoon variability and forcing dynamics in a unipolar icehouse state.…”

Trends and Transitions in Silicate Weathering in the Asian Interior (NE Tibet) Since 53 Ma

“…This coincidence between the emergence or intensification of 100-kyr cycle in the SWI records in the NE Tibetan Plateau and an enhanced EASM, was also reported in previous studies from the NE Tibetan Plateau. For example, Nie et al (2017) and Wang et al (2019Wang et al ( , 2021 pointed out that lake expansion cycles in the Lanzhou, Guide and Qaidam Basins in the Early and Late Miocene were dominated by ~100 kyr eccentricity variance. And they assumed this cycle as derived from the EASM modulated by Antarctic ice sheets at the orbital scale (Nie et al, 2017;Wang et al, 2019;Wang et al 2021).…”

“…For example, Nie et al (2017) and Wang et al (2019Wang et al ( , 2021 pointed out that lake expansion cycles in the Lanzhou, Guide and Qaidam Basins in the Early and Late Miocene were dominated by ~100 kyr eccentricity variance. And they assumed this cycle as derived from the EASM modulated by Antarctic ice sheets at the orbital scale (Nie et al, 2017;Wang et al, 2019;Wang et al 2021). The variations of the Antarctic ice sheets are primarily presented as its intermittent development since ~42 Ma followed by a permanent development since the Eocene-Oligocene transition at 34 Ma, and a subsequent enhancement after the Mid-Miocene Climatic Optimum at 14 Ma (Tripati et al, 2005;Westerhold et al, 2020).…”