East Greenland iceberg photos by Anne Jennings and L. Mikie Smith (Univ. of Colorado)
As a marine sedimentologist, I generally focus on sand and mud as opposed to rocks, and I deal with the relatively recent part of Earth history, i.e., the last 150,000 years, including timescales as short as a tidal cycle, a 2-day storm, or the month-long spring freshet of a river. I study the sources, transport and deposition of Quaternary sediments in coastal and deep marine environments. In coastal and shelf settings, one facet of this work constrains regional relative sea-level change. I also try to estimate the stability of the present sediment deposits and landforms. For example, are coastal dunes growing, shrinking or staying the same, and why?
One tool for tracing materials back to a geological source involves analyzing the geochemical and isotopic signatures of the materials. I have analyzed geochemical sediment tracers (radiogenic isotopes and trace element abundances) to track the provenance of sediments eroded and transported by the Laurentide Ice Sheet. These sediments were deposited in the Labrador Sea during the last ice age (Farmer et al., 2003; Benson et al. 2003). In addition to using this technique for sedimentological and paleoenvironmental questions, I am collaborating with archaeology students and faculty to discern the geochemical provenance of cultural artifacts such as potsherds and carved softstone.
Paleoceanography and Paleoclimatology
Past work has included detailed radiocarbon dating of marine shells from the Hudson Bay region of northeast Canada, aimed at improving our ability to date events in that region (cf. marine reservoir correction database, UW; Barber et al., 1999).
In my lab at Bryn Mawr, my students and I have worked on deep-sea cores by analyzing lithologic parameters such as grain-size, pebble abundance, organic carbon and calcium carbonate concentrations. In collaboration with Prof. Jim Wright at Rutgers University, we also have measured stable oxygen and carbon isotopic compositions of foraminifera shells separated from the core sediments (see Barber and Kraft, 2003 abstract). At the spring 2004 Joint Assembly of the American and Canadian Geophysical Unions in Montreal, I proposed, invited speakers and co-convened a theme session comprising a day and a half of talks and posters focused on the impact of ice-sheet surges and drainage events on the ocean's thermohaline circulation and climate. The broad impetus for these paleooceanographic studies is to help understand the glacial and oceanographic influences that contributed to abrupt global climate changes during the last 30,000 years; especially concerning the 8ka cold event (see 2004 GSA abstract). You can download a .pdf file to view slides from a talk I gave at the Earth System Processes 2 meeting on asynchronous ice discharges to the Labrador Sea during the last ice age. Ultimately, the inferences from this type of research relates to our expectations and predictions regarding the possibility of abrupt climate change in the future.