Sedimentological and Stratigraphic Reconstruction of Ancient Environments and Climates Through Deep Time

  • Greenland Greenland
  • Geysir, in Iceland Geysir, in Iceland

My current research spans the northern and southern hemispheres with field sites in Chile (Atacama Desert), Tanzania (Olduvai Gorge), eastern North America (Nova Scotia to Georgia), and Greenland. The sedimentary strata range in age from Middle Cambrian (~503 Ma), to Triassic-Jurassic (~250-150 Ma), to Miocene-Pliocene (~5.3 Ma), to the Pleistocene (~2 Ma) and Holocene (thousands of years). My research integrates sedimentological and stratigraphic data to interpret depositional environments, paleoclimates, and diagenesis, utilizing field study, petrography (stained thin sections, cathodoluminescence, Scanning Electron Microscopy), stable isotopes (carbon and oxygen), and elemental geochemistry (X-Ray Diffraction, Inducively Coupled Argon Plasma Spectrometery, SEM Energy Dispersion (EDAX)).

One of my research foci is on freshwater limestones with their particular sensitivity to climate. Triassic-Jurassic lacustrine and spring carbonates associated with the Newark Supergroup (eastern North America) rift basins reflect periods of relative tectonic quiescence coupled with Milankovitch-scale wet-dry cycles (4 papers). I am also interested in the preservation potential of microbial forms in carbonate tufas (1 paper).

Miocene-Pliocene lake and wetland freshwater limestones, exposed in the Atacama Desert, Chile, indicate that carbonates may accumulate even during periods of significant aridity, as long as there is sufficient groundwater flow to feed a lacustrine/palustrine system (1 paper, 1 in prep).

Similarly, groundwater may circulate through regional/local faults to precipitate spring carbonates at discrete discharge sites or accumulate in marshy areas where groundwater seeps indicate topographic intersection with a shallow water table. These sites may have been a source of freshwater for hominids in shallow lakes or ponds (3 papers, 1 in prep).

Freshwater carbonates may form in close association with coal deposits, and coal-limestone depositional and diagenetic interactions generate unusual fabrics and textures (western Kentucky) (2 papers).

My second foci is on shallow marine limestones, which may also yield paleoclimate information, at least in terms of relative humidity and tropical or temperate temperatures if supratidal sediments are preserved. Evaporate minerals or evaporite molds in supratidal carbonates suggest an arid climate where subaerial exposure of supratidal shoreline facies resulted in evaporite precipitation (Buffalo Springs Formation, 1 paper in review).

Interpretating marine carbonate rocks provides information about ancient depositional environments. Understanding the strata’s diagenetic history enhances our knowledge of the basin’s evolution and tectonic history. The Jurassic Corallian Formation (southern England) (2 papers), the Cambrian Ledger Formation (south-central Pennsylvania, USA) (5 papers) have added to our understanding of mixed siliciclastic-carbonate depositional systems and microbial reefs with submarine cements, respectively.

In addition to my geological research, I have been deeply involved with issues relating to Women in Science and Academic Leadership, based on my own experience and scholarship. For example, I have written about the value of shared or split academic positions for both an institution and a science couple (3 publications). I have also worked on the “time crunch” women face in terms of the ticking biological and tenure clocks (1 paper), and most recently, my focus is on women in academic leadership roles (1 paper).