Show simple item record Marksamer, Andee Jean 2007-06-22T18:59:32Z 2007-06-22T18:59:32Z 2007-05
dc.description Submitted to the faculty of the University Graduate School in partial fulfillment of the requirements for the degree Master of Science in the Department of Geological Sciences, Indiana University May 2007 en
dc.description.abstract In this study we integrate geophysical, hydrologic, and salinity data to understand the present-day and paleo-hydrology of the Continental Shelf near Nantucket Island, Massachusetts. Time-domain electromagnetic (TDEM) soundings collected across Nantucket and observed salinity profiles from wells indicate that the saltwater/freshwater interface is at least 120 m below sea level in the northern and central portions of the island, far deeper than predicted (80 m) by modern sea level conditions. TDEM soundings also indicate that higher salinity conditions exist on the southern end of the island. These findings suggest a relatively high-permeability environment. Paradoxically, a deep, scientific borehole (USGS 6001) on Nantucket Island, sampling Tertiary and Cretaceous aquifers, is over-pressured by about 0.08 MPa (8 m excess head), which is suggestive of a relatively low-permeability environment. We constructed a series of two-dimensional, cross-sectional models of the paleohydrology of the Atlantic Continental Shelf near Nantucket to understand the flushing history and source of overpressure within this marine environment. We considered two mechanisms for the emplacement of freshwater: (1) meteoric recharge during sea level low stands; and (2) sub-ice-sheet and glacial-lake recharge during the last glacial maximum. Results indicate the sub-ice-sheet recharge from the Laurentide Ice Sheet was needed to account for the observed salinity/resistivity conditions and overpressures. Both TDEM soundings and model results indicate that a lateral transition from fresh to saltwater occurs near the southern terminus of the island due to ice sheet recharge. We also conclude that the overpressure beneath Nantucket represents, in part, “fossil pressure” associated with the last glacial maximum. en
dc.format.extent 995565 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US en
dc.rights This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License. To view a copy of this license, visit or send a letter to Creative Commons, 543 Howard Street, 5th Floor, San Francisco, California, 94105, USA. en
dc.rights.uri en
dc.subject Nantucket Island, Massachusetts en
dc.subject Atlantic Continental Shelf en
dc.subject Ground Water en
dc.subject Hydrogeology en
dc.subject Paleohydrology en
dc.subject Aquifers en
dc.subject Fresh Water en
dc.subject Glacial Geology en
dc.title Integrating Geophysical, Hydrochemical, and Hydrologic Data to Understand the Freshwater Resources on Nantucket Island, Massachusetts en
dc.type Thesis en

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