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Department of Geology
Bryn Mawr College
101 North Merion Avenue
Bryn Mawr, PA 19010
Phone: (610) 526-7392
Fax: (610) 526-5086

RESEARCH - Don Barber

Overview

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.

Coastal Geology

In addition to continuing studies of sediments in the deep North Atlantic Ocean, my students and I carry out research in coastal processes, geomorphology and stratigraphy.  Much of my coastal work pertains to the geomorphological responses of coastlines to sea level rise, and the stability of coastal landforms (barrier islands, beaches and dunes). See our Geomorphology and Coastal Geology pages for more info.

New Jersey

An initial project that pertains to coastal management has been completed on the southern New Jersey shore.  This MA thesis research project by Kristen Bollman employed repeated, high-resolution, 3-D topographic surveys at six beach sites in Stone Harbor and Avalon, NJ.  By quantifying the short-term beach dynamics at these sites, Bollman evaluated the degree to which groins influence the overall sand budget along beaches. The particular management question addressed by this work is whether groin fields should remain in place after beach nourishment has been adopted as a response to erosion.  Bollman's study suggested that groins offer no benefit, and possibly may accelerate offshore sand loss compared with ungroined beaches. Download a .pdf copy of Bollman's thesis (NOTE map figures 1 & 2 are missing; all other are present).

In a smaller study during spring 2005, Brenda Zera (AB Geology '05) revisited the question addressed by Bollman by mapping variability of the nourished beach at Stone Harbor using GPS and Emery beach profiles.

North Carolina

Research in coastal North Carolina focuses on the development of barrier shorelines that presently lie within Pamlico Sound or are landward of the present shoreline. A student project by Kira Diaz Tushman measured topography, vegetation and sedimentology to compare dunes in area grazed by cows with ungrazed dunes along the same beach (see 2002 abstract).  

A differentially corrected Trimble® GPS was used to map the present outline of the North Bay barrier and a series of raised shoreline features on Cedar Island, NC; the modern shoreline has been compared with older air photos and charts in ArcGIS™. The internal stratigraphy of the North Bay barrier and the emerged ridge and swales is being investigated with ground-penetrating radar and shallow hand-auger cores and vibracores.

A project during 2004-05 by Stephanie H. Nebel (AB Geology '05) involved collection, data processing and comparative analysis of offshore seismic profiles and onshore GPR surveys along Bogue and Shackleford Banks. Stephanie presented part of her work as a poster at the March 2005 NE GSA Section Meeting in Saratoga Springs, NY (see abstract). Abby's part of the project has been to analyze sediments collected in vibracores offhshore Shackleford Banks at sites identified by Nebel's geophysical studies. Download the .pdf file and view slides from a talk co-authored with Nebel that Barber gave at the Earth System Processes 2 meeting in Calgary during August 2005. Note that the core analyses were still underway, so this talk focused mostly on the geophysics.

Shallow Subsurface Geophysical Mapping

I have supervised and/or carried out a series of shallow subsurface stratigraphic investigations using the Bryn Mawr Geology Dept's ground-penetrating radar. This work has included:

    1. whether GPR can locate buried stream channels responsible for differential subsidence problems in urban Philadelphia (the short answer is no);
    2. how one can quickly discern ground vs. air reflections and ascertain subsurface penetration depths in the field (see Friedman and Barber abstract, 2001);
    3. evaluating potential Bronze Age tomb sites in Greece; and
    4. mapping the depth and infilling of a stormwater-runoff control pond on the Bryn Mawr campus.