Paleoclimate
Paleoclimate
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1. Carbonate diagenesis and implications for paleoclimate/paleoaltimetry studies
1. Carbonate diagenesis and implications for paleoclimate/paleoaltimetry studies
Top: Carbonate clumped isotope temperatures of the Nima Basin, central Tibet; Right: EPMA (electron probe micro-analysis) elemental mapping of carbonates from the Lunpola Basin, central Tibet
GCA, in preparation; GRL, in preparation.
Right: Carbonate U-Pb dating; Top: Solid-state reordering modeling
Significant questions:
How faithful are “micrites” to recording primary isotopic information and Earth's surface conditions?
Research methods:
Stable isotope and clumped isotope analysis;
Petrographic, CL, and SEM imaging;
Electron probe micro-analysis (EPMA);
Carbonate U-Pb dating and trace element analysis;
Solid-state reordering modeling.
Main findings:
Dolomite may be deposited primarily in rare settings. However, in many cases, the appearance of dolomite, especially with calcite, is a sign of diagenesis;
Silt- to mud-sized detrital carbonate grains could exist in micrite and influence isotope values;
Carbonate clumped isotopes and U-Pb dating are powerful tools to explore diagenesis history;
Lacustrine carbonates in the Nima and Gerze basins in Central Tibet experienced at least two stages of diagenetic alteration, respectively.
2. TILDAS (Tunable infrared laser differential absorption spectrometer)
Top: System schematic of the TILDAS system (Yanay et al., PNAS, 2022); Right: A photo of the TILDAS instruments at the University of Arizona (by Zhennan Wang)
The Environmental Isotope Laboratory at the University of Arizona has led the way in developing the first operational tunable infrared laser differential absorption spectrometer (TILDAS) system to measure clumped isotopes. Compared to the traditional Isotope Ratio Mass Spectrometry method, the TILDAS system provides a much higher sample throughput, requires smaller sample sizes, avoids cardinal mass interference, and reduces analysis costs. This new system is meant to greatly promote high-resolution paleo-temperature reconstructions.
3. Cenozoic aridification processes in Central Asia
A cartoon summarizing various types of authigenic carbonates and the controlling factors of stable oxygen isotopes
Significant question:
When and how did Central Asia get arid?
Research methods:
Lithofacies analysis;
Stable oxygen and carbon isotopes.
Main conclusion:
13–12 Ma regional aridification was mostly likely caused by growing mountain ranges in northern Tibet.
4. Other studies
Late Eocene–Neogene climate changes in Central Asia (NSF pending project)
A large intracontinental shallow sea, the Para-Tethys Sea, existed in central Asia until the late Eocene. The Pamir Plateau and Tian Shan, which are high topography (i.e., >3 km) in central Asia now, did not exist until the Neogene. The interplay between the Para-Tethys Sea retreat and mountain growth significantly modified paleoclimates in central Asia, with contrasting changes on the western (e.g., wetter) and eastern side (e.g., drier) of the Pamir-Tian Shan. This study aims to explore the timing of climate changes and the dominant factors, sea retreat, mountain growth, global cooling, or all.
Late Miocene–Pliocene high-resolution terrestrial climate records (project in plan)
The mid-Pliocene warm period is often cited as a geological analog of the near future if current anthropogenic warming continues. It is essential to explore how paleoclimate and paleoenvironment on land evolved in response to warming during the mid-Pliocene. Previous research by our team on the northern Tibetan Plateau suggested divergent temperature responses between the high Kunlun Mountains and the moderately high basins to the north during the 3.6–2.6 Ma global climate change. Collaborating with Dr. Carmala Garzione and Dr. Junsheng Nie, I am eager to go more into this subject using stable isotopes, clumped isotopes (using the TILDAS system), and other paleoclimate proxies.
5. Other related studies
Paleoclimate shows alpine permafrost accounts for a third of carbon release (Cheng et al., Nature Communication, 2022)
Late Oligocene to early Pliocene wildfire history and links to temperature-driven precipitation changes in Inner Asia (Miao et al., Frontiers in Earth Science, 2022)
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