Our Research

Imagine if the history of life and the environment across all of time and space was put into a book. The SAND(er)S OF Time Lab would want to read that book! But we would also want to know who the authors were and the context in which they lived. We would want to understand the origins of the language it was written in. We would want to study the ink it was printed with, the material of the pages, the meaning behind every stain and crease. Why? Because there is information not only in the text, but in the omission, erasure, and modification of the text.

This is essentially what our lab is all about. Our book is the rock record, the pages are sedimentary deposits, and the ink is in every grain of sand, in every crystal of cement, and in the geometry and composition of every successive layer. The record is autobiographical, its authors and editors being the very physical, chemical, and biological processes that we hope to decipher. This area of study is called taphonomy.

Read on to learn about the specific topics in taphonomy and geobiology that we are working on right now.

What controls phosphate mineralization in the sedimentary record?

All living things need phosphate. Usually, they can get enough from other living things or directly from their environment. But at various times and places throughout Earth history, significant quantities of phosphate have been incorporated into rock and buried — excluded from vigorous biogeochemical cycling. These phosphate deposits are known to contain some of the world's most exquisitely preserved fossil organisms; and phosphate minerals themselves can incorporate trace elements that reflect geochemical conditions at the time of their formation. But what determines when and how such phosphate deposits form? Is it the same across time and space? And are the biologically mediated processes that drive phosphate mineralization at small localized scales (e.g., coprolites and shell molds) responsible for other types of phosphogenesis (e.g., concretions, tissue replacement, pelletal/granular phosphorites)?

Do phosphorites record evidence of microbial-metazoan symbiosis?

Multicellular organisms and phosphate-accumulating bacteria have mutually beneficial relationships that allow them both to regulate their supply of precious phosphate. Can we see those relationships in biologically mediated phosphorite deposits throughout geologic time?

What can problematic microbialites tell us about ecology and sedimentary processes?

Microorganisms love to coalesce, cooperate, coagulate, and generally make a sticky mess. This affects how sediments accumulate (or not), creating textures or patterns that future geobiologists will interpret. Some such textures in the geologic record have eluded interpretation. What processes were necessary to facilitate their formation? Were they principally biological or abiological? Do they have modern analogs?

How might different microbial biosignatures "run the gauntlet" of early digenetic processes?

Teeth, shells, and other mineralized "hard parts" created by living things have a pretty good chance of surviving deposition, burial, and the diagenetic processes that ultimately produce rock from sediment — at least compared to soft, chemically labile organic remains. This is one of many reasons that the fossil record becomes so sparse the older the rocks become. Multicellular individuals generating multiple disarticulating and morphologically distinctive hard parts appears to have been a novelty of the Cambrian! Biomineralization among the single-celled organisms that dominated Archaean through Paleoproterozoic times appears to have been much more limited. Even though this is the bulk of the history of life!

Nevertheless, there are microorganisms that deliberately produce mineralized excrements and/or integuments, some of which may have evolved in Paleoproterozoic times. But how can we identify them in the fossil record? Will their fossils always look like their younger analogs? How are their mineralized excrements changed, morphologically and geochemically, by early diagenetic processes?