Sedimentary framework of the Potomac River estuary, Maryland

Knebel, Harley J.; Martin, E. Ann; Glenn, J.L.; Needell, Sally W.

doi:10.1130/0016-7606(1981)92<578:sfotpr>2.0.co;2

Cited by 12 publications

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“…As a result, the regression was applied to the non-storm samples only. Similar exclusions were Knebel et al (1981) DeFries (1986); Brush et al (1982) Froomer (1980 This study Kerhin et al (1988) Hobbs et al 1986 Schubel and Carter (1976) LI Time intervals are based on pollen horizons, as determined by Brush et al (1982) and DeFries (1986), and sedimentologically significant events for the Chesapeake Bay: (1) 10,008 yr B.P., approximate date of transition from fluvial to estuarine circulation, based on sea-level curves and thalweg depths; (2) 1634 A.D., approximate date of initial European settlements in the Chesapeake watershed (first settlements: Jamestown, Virginia, 1607 A.D.; St. Mary's City, Maryland, 1640 A.D.); (3) 1840 A.D., approximate beginning of "agricultural revival," marked by intensive clearing of the watershed.…”

Section: Methodsmentioning

confidence: 60%

Trends in Chesapeake Bay Sedimentation Rates during the Late Holocene

Donoghue

1990

Quat. res.

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Trends are discernible in the estimates of late Holocene rates of sedimentation and sea-level rise for the Chesapeake Bay. During most of the Holocene Epoch sedimentation rates and relative sea-level rise were equal, within the limits of measurement, at approximately 1 mm yr−1. Sedimentation rates measured over the past century, however, are nearly an order of magnitude higher, while the rate of relative sea-level rise for the Chesapeake Bay now averages 3.3 mm yr−1, as measured on long-term tide gauge records. When the acceleration in these rates occurred is uncertain, but it appears to have been confined to the past millennium, and probably to the past few centuries. The rapid sedimentation rates recorded during historic time may be a temporary disequilibrium that has resulted from a recent acceleration in the rate of relative sea-level rise.

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Section: Methodsmentioning

confidence: 60%

Trends in Chesapeake Bay Sedimentation Rates during the Late Holocene

Donoghue

1990

Quat. res.

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“…In a preliminary report [Purdy et al, 1992] by reports of anomalously low-salinity water near the bottom in the modern Chesapeake Bay channel [Harris, 1976], and by saltwater intrusion at places where the aquifer has been extensively pumped [Drummond, 1988]. Seismic evidence indicates that Pleistocene paleochannels exist offshore nearly 60 m below present sea level [Knebel et al, 1981;Colman et al, 1990]; thus the confining layer overlying the Aquia has been breached at least to this depth. Subsequent to their excavation, each of the paleochannels was naturally back filled with unconsolidated estuarine sediments.…”

Section: Introductionmentioning

confidence: 99%

Aquia Aquifer Dissolved Cl⁻ and ³⁶Cl/Cl: Implications for Flow Velocities

Purdy¹,

Helz²,

Mignerey³

et al. 1996

Water Resources Research

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The Aquia aquifer (southern Maryland) contains a remarkably smooth Cl− profile (0.46–3.23 ppm) along its flow path. This is interpreted as a record of historic changes in the deposition of Cl− in this region. Those changes have been influenced by the rise and fall of sea level, which has altered the distance of the recharge region from the coastline by ∼200 km. The 36Cl concentration along the flow path is not as smooth as the Cl− profile. Historic variations in cosmogenic production, atmospheric transport, precipitation, and evapotranspiration all might have influenced 36Cl concentrations. A general similarity between the 36Cl and Cl− profiles suggests that changes in precipitation and evapotranspiration rates, which influence both tracers similarly, are particularly important. To reconcile 14C, 36Cl, and hydrologic data, we propose a two‐tier model for flow in the Aquia. Shallower portions of the aquifer (<60 m) were subjected to hydraulic gradients and flow rates approximately 5 times larger during the Pleistocene than modern, prepumping rates. At greater depths, flow rates were much slower and less variable; water in this region may be old enough to record some 36Cl decay.

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Sediment source variations and lead‐210 inventories in recent Potomac Estuary sediment cores

Oldfield

Maher

Appleby

1989

J Quaternary Science

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We present the results of magnetic measurements (low field susceptibility, anhysteretic and isothermal remanences) on samples of sediment from 1 1 cores from the Potomac River between Washington DC and its mouth. The magnetic properties indicate that at sites in the upstream reaches especially, there has been a shift to surface-soil-derived sediments in recent times. No such shift is indicated at the mouth ofthe Estuary. Comparison with pollen, ""Pb and trace metal analyses, where available, suggests that the shift to soil-derived material dates from the early to mid-1 9th century and coincides with a major land use change previously documented by Brush eta/. (1 982). Inventories of Journal of Quaternary Science unsupported (excess) ""Pb activity in the cores increase upstream, are positively correlated with total sedimentation rates, and, in the upper reaches where the magnetic properties indicate soil inwash, greatly exceed values expected from direct atmospheric deposition alone. We infer that in these cores, most of the unsupported ""Pb is deposited from the surfaces of the catchment as a result of soil erosion.

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Sedimentary framework of the Potomac River estuary, Maryland

Cited by 12 publications

References 0 publications

Trends in Chesapeake Bay Sedimentation Rates during the Late Holocene

Trends in Chesapeake Bay Sedimentation Rates during the Late Holocene

Aquia Aquifer Dissolved Cl⁻ and ³⁶Cl/Cl: Implications for Flow Velocities

Sediment source variations and lead‐210 inventories in recent Potomac Estuary sediment cores

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Sedimentary framework of the Potomac River estuary, Maryland

Cited by 12 publications

References 0 publications

Trends in Chesapeake Bay Sedimentation Rates during the Late Holocene

Trends in Chesapeake Bay Sedimentation Rates during the Late Holocene

Aquia Aquifer Dissolved Cl− and 36Cl/Cl: Implications for Flow Velocities

Sediment source variations and lead‐210 inventories in recent Potomac Estuary sediment cores

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Product

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Aquia Aquifer Dissolved Cl⁻ and ³⁶Cl/Cl: Implications for Flow Velocities