RESEARCH: from macro-scale tectonics to molecular fossils

Major areas of research interests include:

  • Growth history and driving forces of Tibetan Plateau
  • Asian monsoons and Westerlies
  • C4-grassland expansion
  • Eocene-Oligocene Transition
  • Martian analog studies
  • Biogeochemical cycles

My research career began with a research project on the northern Tibetan Plateau that includes the intermountain Qaidam Basin, the foreland basin of Hexi Corridor, the Qilian Shan fold-thrust-belt, and the left-lateral strike-slip Altyn Tagh fault. To understand the growth history and the climatic impact of the northern Tibetan Plateau, I used an integrated approach (basin analysis, U-Th/He thermochronology, and carbonate stable oxygen and carbon isotopes).

Motivations_forMyWeb
Topographic map, showing the study locations and types of research in the northern Tibetan Plateau and the climatic regimes (arrows). Note: Major structures the Chinese Loess Plateau (brownish color) are denoted (barbed lines – thrust fault systems; pairs of arrows – strike-slip fault systems); AA’ denotes the topographic cross-section shown below.

My interests in biogeochemistry processes (biosynthesis processes and isotope effects) trace back to my first postdoctoral training in Pagani’s lab at Yale. I was recruited by Mark Brandon who encouraged me to investigate the use of leaf wax isotopes in tectonics. I sincerely thank him for this great opportunity to broaden my vision in research. I started with the compound-specific isotope analysis on n-alkanes and biomarker analysis. I have developed an approach that used the leaf wax n-alkane hydrogen isotopes and microbial tetraethers to quantify the paleo-elevation of Qaidam Basin and the paleo-relief between the Qilian Shan and the bounding basins (Qaidam Basin and Hexi Corridor) (see details in my publications: Zhuang et al., 2014 EPSL and Zhuang et al., 2019 GRL).

Topographic cross-section through the Himalaya across the Tibetan Plateau with major geological features in the northern Tibetan Plateau being labeled (right). Note: Qaidam Basin – the largest intermountain basin on the plateau; Hexi Corridor – foreland basin.

I have used a proxy (isoprenoid GDGT) to constrain the upwelling history in the western Arabian Sea by reconstructing the sea surface temperatures at Ocean Drilling Program (ODP) Sites 722B and 730A in the core cell of upwelling areas in the western Arabian Sea.

Himalaya-Tibetan Plateau with active faults (barbed lines, thrust; paired arrows, strike-slip) and surrounding regions. Green circles indicate ODP sites 730A and 722B with SST contours and winds in summer. Hexagons denote paleoaltimetry studies, supporting an Eocene proto-Plateau (red) and expansion of high topography in Neogene (yellow). Yellow triangles indicate themochronology studies, revealing rapid uplift in Pamir and Iranian Plateau in the Middle-Late Miocene. Yellow squares are faunal and sedimentary studies that support the restriction and disruption of Tethys Seaway in the Middle Miocene.

My group has used the leaf wax n-alkane hydrogen and carbon isotopes, biomarkers, along with the climatic modeling to understand the evolution of Asian summer monsoons and the interactions with the Westerlies on Myr- and Kyr-scales, and the Eocene-Oligocene Transition in Asia and North America (see Hou et al., 2020 GSA Bulletin; Wu et al., 2021 EPSL for details).

30 year (1981-2010) record of winter (December-January-February) minus summer (June-July-August) precipitation (mm/day). Blue color represents greater precipitation in winter (December-January-February), while red color indicates greater precipitation in summer (June-July-August). Data are derived from NCEP Reanalysis provided by NOAA ESRL PSD at Colorado, Boulder, USA (https://www.esrl.noaa.gov/psd/data). The gray line outlines the 3000 m-contour on the Tibetan Plateau and surrounding mountain (adapted from Li et al., 2018). The Qaidam Basin (brown outline), core site (yellow star), and the Chinese Loess Plateau (CLP; dark blue outline) are noted. Arrows highlight the moisture transport via the Westerlies (green), Indian summer monsoon (blue), and East Asian summer monsoon (yellow). The black dashed line represents the modern boundary between the Asian summer monsoons (East Asian and Indian summer monsoons) and the Westerlies. Blue triangles are the location of isotope reconstruction of paleometeoric waters in the Hulu (H) (Wang et al., 2008), Dongge (G) (Dykoski et al., 2005), and Kesang (K) (Cheng et al., 2012) caves and the Dunde Ice core (D) (Thompson et al., 1989). Green circles denote the lakes and paleo-lakes discussed in the text: Lake Qinghai (QH) (Hou et al., 2016), Lake Sugan (S) (He et al., 2013Wang et al., 2013), Lake Keluke (H) (Rao et al., 2014), Tengger Desert (T), Qarhan (Q), Zabuye (Z), Aksayqin (A) (Yu et al., 2003) and Lisan (L) (Bartov et al., 2003). Black squares indicate the Global Network of Isotope in Precipitation (GNIP) meteorological stations (IAEA/WMO, 2006).

The n-alkane and GDGT skills that my group has used comprise a tiny portion of organic matters preserved in sediments and sedimentary rocks (see diagram below). I am very interested in other organic molecules. I am spending time and effort to expand knowledge in biogeochemistry via a top-down way to revolutionize my research vision, tracing from the preservation of organic matters in lithosphere to biosphere where the organic matters are synthesized and finally to the substrates that are supplied from the atmosphere and hydrosphere.

2.topdown
Diagram emphasizing a top-down way to expand my vision and explore new research frontiers. R, O, and OH represent the alkyl, carbonyl, and hydroxyl functional groups, respectively; single (double) segments are saturated C-C (unsaturated C = C) bonds. Three arrow lines in the middle link the main categories of organic molecules (bold fonts within rectangle boxes) in sediments and sedimentary rocks with organisms in biosphere where they are synthesized via different pathways (acetogenic; mevalonate pathway – MVA; and methylerythritol phosphate or non-mevalonate pathway – MEP). The bottom arrow line highlights the inorganic substrates (CO2 and H2O) in the atmosphere and hydrosphere to sustain the biosynthesis processes in biosphere.