Integrating geophysical, hydrochemical, and hydrologic data to understand the freshwater resources on Nantucket Island, Massachusetts

Marksamer, Andee; Person, Mark; Day‐Lewis, Frederick D.; Lane, John W.; Cohen, Denis; Dugan, Brandon; Kooi, H.; Willett, Mark

doi:10.1029/171gm12

Cited by 22 publications

(49 citation statements)

References 49 publications

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“…(c) Measured head data comparing shallow water table head in Nantucket well 228 (circles) and head within deeper Cretaceous aquifers in U.S. Geological Survey well 6001 (squares). The comparison of the data shows that the aquifers are not related and that the deeper Cretaceous aquifer has anomalously higher pressure, which is interpreted to be glacial in origin [Marksamer et al, 2007].…”

Section: Introductionmentioning

confidence: 99%

“…This overpressure cannot be produced by the low, local fluvial sedimentation rates and sediment properties in the region [Marksamer et al, 2007]. The overpressure may be a relic of Pleistocene sea level rise and fall and ice sheet loading .…”

Section: Introductionmentioning

confidence: 99%

“…The continental margin off Massachusetts was repeatedly glaciated throughout the late Pleistocene [Oldale and O'Hara, 1984;Uchupi et al, 2001;Siegel et al, 2012]. Two-and three-dimensional paleohydrologic models simulate how these glacial cycles, in combination with sea level fluctuations, had a strong influence on the offshore hydrogeologic system [Person et al, 2003;Marksamer et al, 2007;Cohen et al, 2010]. In particular, the models show that these glaciation cycles may have emplaced large volumes of subsurface freshwater tens of kilometers beyond the edge of the ice sheets [Person et al, 2003;Marksamer et al, 2007;Cohen et al, 2010].…”

Section: Introductionmentioning

confidence: 99%

“…Two-and three-dimensional paleohydrologic models simulate how these glacial cycles, in combination with sea level fluctuations, had a strong influence on the offshore hydrogeologic system [Person et al, 2003;Marksamer et al, 2007;Cohen et al, 2010]. In particular, the models show that these glaciation cycles may have emplaced large volumes of subsurface freshwater tens of kilometers beyond the edge of the ice sheets [Person et al, 2003;Marksamer et al, 2007;Cohen et al, 2010]. A glacial influence on this hydrogeologic system may also explain lowsalinity groundwater observed on Nantucket Island [Folger et al, 1978].…”

Section: Introductionmentioning

confidence: 99%

“…Siegel et al [2012] show that the continental shelf off Massachusetts was glaciated in the late Pleistocene. Marksamer et al [2007] show that the Last Glacial Maximum (LGM) may have increased overpressure tens of kilometers beyond the maximum extent of the Laurentide ice sheet. We suggest that the bright spots observed in the seismic data could be regions of localized overpressure generated during late Pleistocene glaciations.…”

Section: Introductionmentioning

confidence: 99%

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Glacially generated overpressure on the New England continental shelf: Integration of full‐waveform inversion and overpressure modeling

et al. 2014

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Localized zones of high-amplitude, discontinuous seismic reflections 100 km off the coast of Massachusetts, USA, have P wave velocities up to 190 m/s lower than those of adjacent sediments of equal depth (250 m below the sea floor). To investigate the origin of these low-velocity zones, we compare the detailed velocity structure across high-amplitude regions to adjacent, undisturbed regions through full-waveform inversion. We relate the full-waveform inversion velocities to effective stress and overpressure with a power law model. This model predicts localized overpressures up to 2.2 MPa associated with the high-amplitude reflections. To help understand the overpressure source, we model overpressure due to erosion, glacial loading, and sedimentation in one dimension. The modeling results show that ice loading from a late Pleistocene glaciation, ice loading from the Last Glacial Maximum, and rapid sedimentation contributed to the overpressure. Localized overpressure, however, is likely the result of focused fluid flow through a high-permeability layer below the region characterized by the high-amplitude reflections. These high overpressures may have also caused localized sediment deformation. Our forward models predict maximum overpressure during the Last Glacial Maximum due to loading by glaciers and rapid sedimentation, but these overpressures are dissipating in the modern, low sedimentation rate environment. This has important implications for our understanding continental shelf morphology, fluid flow, and submarine groundwater discharge off Massachusetts, as we show a mechanism related to Pleistocene ice sheets that may have created regions of anomalously high overpressure.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Glacially generated overpressure on the New England continental shelf: Integration of full‐waveform inversion and overpressure modeling

et al. 2014

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Influence of late Pleistocene glaciations on the hydrogeology of the continental shelf offshore Massachusetts, USA

Siegel

Person

Dugan

et al. 2014

Geochem Geophys Geosyst

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Multiple late Pleistocene glaciations that extended onto the continental shelf offshore Massachusetts, USA, may have emplaced as much as 100 km 3 of freshwater (salinity <5 ppt) in continental shelf sediments. To estimate the volume and extent of offshore freshwater, we developed a three-dimensional, variable-density model that couples fluid flow and heat and solute transport for the continental shelf offshore Massachusetts. The stratigraphy for our model is based on high-resolution, multichannel seismic data. The model incorporates the last 3 Ma of climate history by prescribing boundary conditions of sea level change and ice sheet extent and thickness. We incorporate new estimates of the maximum extent of a late Pleistocene ice sheet to near the shelf-slope break. Model results indicate that this late Pleistocene ice sheet was responsible for much of the emplaced freshwater. We predict that the current freshwater distribution may reach depths up to 500 meters below sea level and up to 30 km beyond Martha's Vineyard. The freshwater distribution is strongly dependent on the three-dimensional stratigraphy and ice sheet history. Our predictions improve our understanding of the distribution of offshore freshwater, a potential nonrenewable resource for coastal communities along recently glaciated margins.

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Rapid sedimentation and overpressure in shallow sediments of the Bering Trough, offshore southern Alaska

et al. 2017

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Pore pressures in sediments at convergent margins play an important role in driving chemical fluxes and controlling deformation styles and localization. In the Bering Trough offshore Southern Alaska, extreme sedimentation rates over the last 140 kyr as a result of glacial advance/retreats on the continental shelf have resulted in elevated pore fluid pressures in slope sediments overlying the Pamplona Zone fold and thrust belt, the accretionary wedge resulting from subduction of the Yakutat microplate beneath the North American Plate. Based on laboratory experiments and downhole logs acquired at Integrated Ocean Drilling Program Site U1421, we predict that the overpressure in the slope sediments may be as high as 92% of the lithostatic stress. Results of one‐dimensional numerical modeling accounting for changes in sedimentation rate over the last 130 kyr predicted overpressures that are consistent with our estimates, suggesting that the overpressure is a direct result of the rapid sedimentation experienced on the Bering shelf and slope. Comparisons with other convergent margins indicate that such rapid sedimentation and high overpressure are anomalous in sediments overlying accretionary wedges. We hypothesize that the shallow overpressure on the Bering shelf/slope has fundamentally altered the deformation style within the Pamplona Zone by suppressing development of faults and may inhibit seismicity by focusing faulting elsewhere or causing deformation on existing faults to be aseismic. These consequences are probably long‐lived as it may take several million years for the excess pressure to dissipate.

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Integrating geophysical, hydrochemical, and hydrologic data to understand the freshwater resources on Nantucket Island, Massachusetts

Cited by 22 publications

References 49 publications

Glacially generated overpressure on the New England continental shelf: Integration of full‐waveform inversion and overpressure modeling

Glacially generated overpressure on the New England continental shelf: Integration of full‐waveform inversion and overpressure modeling

Influence of late Pleistocene glaciations on the hydrogeology of the continental shelf offshore Massachusetts, USA

Rapid sedimentation and overpressure in shallow sediments of the Bering Trough, offshore southern Alaska

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