The Athel silicilyte is an enigmatic, hundreds of meters thick, finely laminated quartz deposit, in which silica precipitated in deep water (>~100–200 m) at the Ediacaran–Cambrian boundary in the South Oman Salt Basin.
Earth scientists can glean clues about the nature of Earth's ancient environments from a variety of clues: sedimentary textures and structures, chemical and isotopic compositions, microscopic to macroscopic fossils, and others. At Caltech we approach this problem from both ends of the time scale – working on modern analog organisms and environments to understand the signals they preserve, and on ancient sediments and rocks to try to decipher what the Earth was like thousands, millions, or billions of years ago.
Recent projects include:
A multidisciplinary study of the Neoproterozoic Athel Silicylite, using sedimentary fabrics, inorganic isotopic records, and organic biomarkers to propose a new model for this geologically unique unit (Grotzinger, Sessions, Eiler)
At Caltech we developed a novel method for measuring sulfur isotopes in nanogram quantities of sulfate in carbonate rocks, and used it to provide the first empirical constraints on sulfur cycling in the Archean oceans (Adkins, Fischer, Sessions)
Clumped isotope carbonate reconstructions?
Using the hydrogen isotope ratios of leaf-wax biomarkers, we reconstructed the hydroclimate of western Sumatra over the past 15,000 years and showed it varied much less than did the western equatorial Pacific.