Join us for a hybrid lunch in March

WEDNESDAY, APRIL 1, 2026

JOIN US IN PERSON OR oNLINE

Talk Title: "IODP³-NSF Expedition 501: Offshore Freshened Groundwater and “Aquifer” Systems in the New England Continental Shelf"

Speaker: Brandon Dugan, Colorado School of Mines

IODP3-NSF Expedition 501 drilled three sites along a 45 km-long, NNW-SSE transect on the southern New England continental shelf offshore Nantucket and Martha’s Vineyard to characterize an extensive offshore freshened groundwater (OFG) system. Each site was investigated with drilling, coring, wireline logging, and groundwater pumping. Long-term observatories were installed in two offshore sites to monitor formation resistivity, temperature, and pressure. Visual core description, smear slide analyses, and core and downhole petrophysical logging document an unconsolidated sedimentary package consisting of alternating layers of sand and mud. The deeper sedimentary section is Cretaceous and was deposited in a terrestrial environment. The shallow sedimentary section ranges from Paleocene to Pleistocene and was deposited in a marine environment. Interstitial water and pumped groundwater from the nearshore sites document a transition from seawater salinity to less than 2% of seawater salinity within the upper 125 mbsf. Furthest offshore, two freshened zones with salinity that is ~50% of seawater salinity exist above 300 mbsf. The freshened water salinity is consistent throughout marine and terrestrial sediments both mud-rich and sand-rich. Preliminary isotope analysis suggested the freshened water is of Late Pleistocene origin. Compared to salinity, interstitial water chemistry, including alkalinity, sulfide, and ammonium concentrations, demonstrates more nuanced patterns, with distinct profiles as well as absolute values downcore. This integrated research program elucidates the complexity of the freshened system beneath the southern New England shelf, and has implications for understanding other OFG systems worldwide.

Biography:

Brandon is a professor and associate department head of Geophysics at Colorado School of Mines. Before joining Mines, Brandon earned a bachelor's degree in geo-engineering from the University of Minnesota, Twin Cities and a Ph.D. in geosciences from Penn State University, completed a Mendenhall post-doctoral fellowship with the US Geological Survey, and was a professor of Earth Science at Rice University. In his research, he couples theory, experiments, and models to understand the interactions of fluids and solids in Earth’s shallow crust. As part of his research, Brandon regularly participates in field programs which has led to him spending about 2 years of his life on research vessels in our oceans. For research and teaching contributions, Brandon received the Asahiko Taira International Scientific Ocean Drilling Research Prize (2018) and a Blue Key Honor Society/Tau Beta Pi Outstanding Faculty Award (2017).

Download Abstract and Bio

Hybrid luncheon schedule:

• 11:15am: In-person check-in opens
• 11:30: Lunch service begins
• 12:00pm: Online event opens
• 12:15pm: Talk begins
• 1:00pm: Talk/Q&A session ends; Online event closes

Hybrid Luncheon costs:

• Member Lunch: $35
• Non-Member Lunch: $40
• Walk-in without Lunch: $15
• Member Online: $10
• Non-member Online: $20
• Student online: Free

Refund policy:

If you need to cancel an in-person lunch registration for any reason, you must do so by 4:00pm on the Thursday before the Wednesday luncheon. Refunds will not be available after 4:00pm on the Thursday before the luncheon. If you are unable to attend, your luncheon registration is transferable to another RMAG member, or if you are a non-member your registration is transferable to whomever you wish. Refunds will not be issued for online talk registrations.

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