Geologic map of the Urbana quadrangle, Frederick and Montgomery Counties, Maryland
No abstract available.
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Geology topics
Research about Maryland
Source-linked reports with geographic coverage including Maryland.
Hydrogeologic setting and potential for denitrification in ground water, Coastal Plain of southern Maryland
The types and distribution of Coastal Plain sediments in the Patuxent River Basin may contribute to relatively low concentrations of nitrate (typically less than 1 milligram per liter) in stream base flow because of the chemical reduction of dissolved nitrate (denitrification) in ground water. Water chemistry data from synoptic stream base-flow surveys in the Patuxent River Basin show higher dissolved nitrate concentrations in the Piedmont than in the Coastal Plain section of the watershed. Stream base flow reflects closely the chemistry of ground water discharging from the surficial (unconfined) aquifer to the stream. Because land use in the sampled subbasins is virtually the same in each section, differences in the physical and geochemical characteristics of the surficial aquifer may explain the observed differences in water chemistry. One possible cause of lower nitrate concentrations in the Coastal Plain is denitrification within marine sediments that contain chemically reduced compounds. During denitrification, the oxygen atoms on the nitrate (N0 3 -) molecule are transferred to a reduced compound and N gas is produced. Organic carbon and ferrous iron (Fe 2+ ), derived from the dissolution of minerals such as pyrite (FeS 2 ) and glauconite (an iron aluminosilicate clay), can act as reducing substrates; these reduced chemical species are common in the marine and estuarine deposits in Southern Maryland. The spatial distribution of geologic units and their lithology (sediment type) has been used to create a map of the potential for denitrification of ground water in the surficial aquifer of the Coastal Plain in Southern Maryland.
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Atlantic Flyway review: Piedmont-Coastal Plain, Region IV, Fall 1999: Robbins Nest, Laurel, MD (390-0765)
This is the first of three stations along the Patuxent River. Elevation here at the edge of the Piedmont ranges from 265 ft at the house to 160 ft at the river. In spite of easterly winds and heavily overcast skies from Hurricanes Dennis, Floyd, and Irene, we suffered from drought all summer, not rain. We had only about two inches each in June and July, 4.55 in August, then a whopping 16.03 in September, and a normal 3.46 in October. This station operates all day on weekends, but only before and after work on other days. Net-hours were 5% above the 26-year mean of 3655, but way down from last year because other commitments kept me out of town on several weekends. I had only 14 days when I could net all day. Although the most birds were banded on opening day, the most per net-hour were on 19 and 15 October and 23 September. The nets caught 26 returns from prior years, the oldest being a seven-year-old Blue Jay and a seven-year-old cardinal. To illustrate how biased a sample one can obtain from netting, I captured only one junco in the nets, but caught 47 of them in baited traps on our deck. Other species taken only in the traps (and not included in the totals) were Mourning Dove, Chipping Sparrow, House Finch, Pine Siskin, and American Goldfinch.
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Atlantic Flyway review: Piedmont-Coastal Plain, Region IV, Fall 1999: Patuxent powerline right-of-way (390-0764)
Fall 1999 was among the poorest seasons in this banding station's 20 years of operation. Record high capture totals were set for only two species: Ruby-throated Hummingbird (41 individuals captured, none banded; previous high 21) and White-breasted Nuthatch (two individuals banded; previous high, one). The only other species that stood out as being unusually numerous was Blackpoll Warbler, for which the banding total (33 birds) was the highest since 1988. Bandings of several species (Red-eyed Vireo, Tennessee Warbler, Nashville Warbler, Ovenbird, Hooded Warbler, Canada Warbler, Eastern Towhee, and Field Sparrow) were at record lows, and bandings of many other species were below the long-term (1980-1998) mean. The number of species banded was also below the long-term mean of 86 species, and tied the previous low. Possible contributing factors included drought conditions in Maryland and elsewhere in the East, which may have influenced nesting productivity and migration dates for some species; Hurricanes Dennis and Floyd, which influenced East Coast weather through much of September; the unprecedented scarcity of Hercules' Club ( Aralia spinosa ) fruits at the banding station; and occasional visits by a gray fox, which reduced operation of some nets in October and November. A season highlight was the August capture of 37 Red-eyed Vireos banded at this station in previous years, including a bird banded in August 1989. These are almost certainly locally nesting birds that feed on the abundant fruits of Viburnum dentatum in the powerline right-of-way in late summer. Regular assistants at the banding station included Woody Martin, Susie Michaelson, Jane Nicolich, Gemma Radko, Jack Saba, Julie Tomita, and Laurie Walter. Danny Bystrak and Mary Gustafson each served as bander-in-charge on several mornings.
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Index of hydrologic characteristics and data resources for the Gwynns Falls watershed, Baltimore County and Baltimore City, Maryland
The Gwynns Falls watershed has been selected as the primary study area for the Baltimore Ecosystem Study, as part of the National Science Foundation's Long-Term Ecological Research program. Because the Baltimore Ecosystem Study will be investigating long-term hydrologic changes in the Gwynns Falls watershed, a compilation of existing data resources for the watershed is necessary. This report discusses hydrologic characteristics and presents a compilation of historical data resources for the Gwynns Falls watershed. Tables are presented that list active and discontinued continuous-record streamflow-gaging stations, nontidal crest-stage partial-record stations, low-flow partial-record stations, and water-quality partial-record stations operated by the U.S. Geological Survey, Maryland-Delaware-D. C. District, in the Gwynns Falls watershed. Statistics regarding the number of inventoried ground-water wells in or bordering the Gwynns Falls watershed also are presented. A summary of additional data resources for the Gwynns Falls watershed is provided. This includes (1) an inventory of selected U.S. Geological Survey studies and reports that contain historical data or basin characteristics for streams in the watershed, (2) a listing of indirect flood-discharge measurements that have been made at several monitoring stations in the watershed, (3) a brief discussion of channel-stability and bridge-scour data collected by the U.S. Geological Survey in the watershed during 1990?95, (4) a listing of climatological data stations in the watershed and in the surrounding regional area, and (5) a listing of other selected reports that include data or information on the Gwynns Falls watershed.
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Organic compounds and trace elements in the Pocomoke River and tributaries, Maryland
In response to concern about recent blooms of the dinoflagellate, Pfiesteria piscicida, samples of sediment and water were collected from the lower Pocomoke River Basin and were screened for trace elements, pesticides, and other organic compounds. A large group of steroid and fatty acid methyl-ester compounds was detected in streamwater using gas chromatography/mass spectroscopy in scan mode. Some of these steroid compounds have been identified and further quantified in bed-sediment extracts. Spatial patterns of the concentrations of cholesterol suggest that these compounds are linked to the runoff of animal wastes into the river. Many of the organic compounds found in the Pocomoke River sediments have not yet been identified, but at least several are in the class of hormone compounds related to estradiols and have the potential to promote endocrine-disrupting effects in aquatic life. Particulate forms of arsenic and zinc are slightly elevated above normal levels for streams, but the sources for these elements are still undetermined. Several pesticides were found in low, parts-per-trillion concentrations, but were within the ranges commonly found in streams of this region.
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Potentiometric surface of the Aquia aquifer in southern Maryland, September 1997
No abstract available.
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Potentiometric surface of the upper Patapsco aquifer in southern Maryland, September 1997
This report presents a map showing the potentiometric surface of the Upper Patapsco aquifer in the Patapsco Formation of Cretaceous age in Southern Maryland during September 1997. The map was prepared from water-level measurements in 42 wells. The potentiometric surface was 122 feet above sea level near the northern boundary and outcrop area of the aquifer in a topographically high area of Anne Arundel County, and 57 feet above sea level in a similar setting in Prince Georges County. From these high areas, the potentiometric surface declined to the southeast toward large well fields in the Annapolis area and Arnold and from all directions toward a cone of depression southwest of Waldorf. Ground-water levels reached 20 feet below sea level in the Annapolis area, 28 feet below sea level at Arnold, and 118 feet below sea level southwest of Waldorf.
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The difference between the potentiometric surfaces of the upper Patapsco aquifer, September 1990 and September 1997 in southern Maryland
This report presents a map that shows the change in the potentiometric surface of the Upper Patapsco aquifer in the Upper Patapsco Formation of Cretaceous age in Southern Maryland for September 1990 and September 1997. The map, based on water-level measurements in 38 wells, shows that the change of the potentiometric surface during the 7-year period ranged from zero in the most northern part of the study area, which is near the outcrop of the aquifer, to a decline of 19 feet at LaPlata, which is near the most southwestern part of the study area.
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The difference between the potentiometric surfaces of the lower Patapsco Aquifer, September 1990 and September 1997 in southern Maryland
This report presents a map that shows the change in the potentiometric surface of the Lower Patapsco aquifer in the Lower Patapsco Formation of Cretaceous age in Southern Maryland for September 1990 and September 1997. The map, based on water-level measurements in 53 wells, shows that the change of the potentiometric surface during the 7-year period ranged from rises of 8 feet at Indian Head and 1 foot near the outcrop area in Glen Burnie to declines of 39 feet at Arnold, 37 feet at Waldorf, and 37 feet at Morgantown.
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Ground-water discharge and nitrate loadings to the coastal bays of Maryland
Nitrate in ground water discharged to the Atlantic coastal bays of Maryland enhances the growth of phytoplankton and algae in the bays, which in turn contributes to the process of eutrophication (changes in a body of water as nutrients and sediments accumulate), which is one of the principal environmental problems in the bays. Information on nitrate loading to the bays has been identified as a major data gap by State and Federal resource managers. This report presents results of a study to estimate ground-water discharge and potential nitrate loads to the coastal bays of Maryland, which include Chincoteague, Newport, Sinepuxent, Isle of Wight, and Assawoman Bays. The nitrate load from the discharge of ground water to the coastal bays is dependent on the concentration of nitrate in the water and the volume of ground water being discharged. Data from 388 wells completed in the surficial aquifer that discharges to the bays were used to construct a map of the distribution of nitrate concentration in the ground water. On the basis of those data, and on several simplifying assumptions, the potential nitrate load to the coastal bays from direct discharge of ground water was estimated to be 272,000 pounds of nitrate per year, distributed throughout the 108-square-mile surface area of the bays. Nitrate from ground water can also enter the coastal bays by way of base flow to streams that discharge to the bays. The potential nitrate load to the bays from the base flow of streams was estimated to be 862,000 pounds per year, assuming that the concentration of nitrate in stream base flow is 3.2 milligrams per liter, which is the median concentration of nitrate in ground water in the study area.
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Comparison of hydrochemical tracers to estimate source contributions to peak flow in a small, forested, headwater catchment
Three-component (throughfall, soil water, groundwater) hydrograph separations at peak flow were performed on 10 storms over a 2-year period in a small forested catchment in north-central Maryland using an iterative and an exact solution. Seven pairs of tracers (deuterium and oxygen 18, deuterium and chloride, deuterium and sodium, deuterium and silica, chloride and silica, chloride and sodium, and sodium and silica) were used for three-component hydrograph separation for each storm at peak flow to determine whether or not the assumptions of hydrograph separation routinely can be met, to assess the adequacy of some commonly used tracers, to identify patterns in hydrograph-separation results, and to develop conceptual models for the patterns observed. Results of the three-component separations were not always physically meaningful, suggesting that assumptions of hydrograph separation had been violated. Uncertainties in solutions to equations for hydrograph separations were large, partly as a result of violations of assumptions used in deriving the separation equations and partly as a result of improper identification of chemical compositions of end-members. Results of three-component separations using commonly used tracers were widely variable. Consistent patterns in the amount of subsurface water contributing to peak flow (45-100%) were observed, no matter which separation method or combination of tracers was used. A general conceptual model for the sequence of contributions from the three end-members could be developed for 9 of the 10 storms. Overall results indicated that hydrochemical and hydrometric measurements need to be coupled in order to perform meaningful hydrograph separations.
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Technique for simulating peak-flow hydrographs in Maryland
The efficient design and management of many bridges, culverts, embankments, and flood-protection structures may require the estimation of time-of-inundation and (or) storage of floodwater relating to such structures. These estimates can be made on the basis of information derived from the peak-flow hydrograph. Average peak-flow hydrographs corresponding to a peak discharge of specific recurrence interval can be simulated for drainage basins having drainage areas less than 500 square miles in Maryland, using a direct technique of known accuracy. The technique uses dimensionless hydrographs in conjunction with estimates of basin lagtime and instantaneous peak flow. Ordinary least-squares regression analysis was used to develop an equation for estimating basin lagtime in Maryland. Drainage area, main channel slope, forest cover, and impervious area were determined to be the significant explanatory variables necessary to estimate average basin lagtime at the 95-percent confidence interval. Qualitative variables included in the equation adequately correct for geographic bias across the State. The average standard error of prediction associated with the equation is approximated as plus or minus (+/-) 37.6 percent. Volume correction factors may be applied to the basin lagtime on the basis of a comparison between actual and estimated hydrograph volumes prior to hydrograph simulation. Three dimensionless hydrographs were developed and tested using data collected during 278 significant rainfall-runoff events at 81 stream-gaging stations distributed throughout Maryland and Delaware. The data represent a range of drainage area sizes and basin conditions. The technique was verified by applying it to the simulation of 20 peak-flow events and comparing actual and simulated hydrograph widths at 50 and 75 percent of the observed peak-flow levels. The events chosen are considered extreme in that the average recurrence interval of the selected peak flows is 130 years. The average standard errors of prediction were +/- 61 and +/- 56 percent at the 50 and 75 percent of peak-flow hydrograph widths, respectively.
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Atlantic Flyway review: Piedmont-Coastal Plain Region IV - Fall 1997: Robbins Nest, Laurel, MD (390-0765)
The 25th year of fall banding at this back yard station atop the Patuxent River gorge between Laurel and the 1-95 bridge netted more birds of summer and winter resident species than migrants. Myrtle Warbler was the only one of the six commonest species captured that is primarily a transient here. My 5214 net-hours, my fourth highest, were 48% above the 24-year mean of 3512, but the only species to exceed their previous high were Carolina Chickadee and Magnolia Warbler. Part of the reason for my low catch per 100 net-hours in recent years is the dieoff of dogwood from anthracnose and destruction of the shrub layer in my mature woods by an overpopulation of deer. For the first time, deer destroyed three of my nets. We also had the driest summer in decades, which killed some of the shallow-rooted vegetation this year. The greatest declines from last year were in catbird (51 to 32), Hermit Thrush ( 27 to 12 ), and Blackand-white Warbler (11 to 3), and the greatest increases were in Myrtle Warbler (2 to 34), Carolina Chickadee (6 to 36), and Tufted Titmouse (10 to 31). The biggest changes from the mean of the first five years (1973-77) to the most recent five years (1993-97), not corrected for the 147% increase in net-hours, are increases in Rubythroated Hummingbird (1.2 to 7.6 ), Black-throated Blue Warbler (1.8 to 11.6), Common Yellowthroat (5.0 to 17.6), and House Finch (0.2 to 6.0), and decreases in Swainson's Thrush (26.6 to 17.2), Gray-cheeked/Bicknell's Thrush (9.4 to 3.8), Scarlet Tanager (6.6 to 2.2), and American Goldfinch (3.0 to 0.4). The oldest of my 39 returns were a six-year-old Gray Catbird and a five-year-old Carolina Chickadee. Two birds banded here during the fall migration of 1995 were found to the northeast of here in the summer of 1997: a Ruby-throated Hummingbird (8000-85102) in Philadelphia, PA, and a Hermit Thrush (1521-58503) at Wentworth, NH. A Savannah Sparrow was the 121st species banded on our suburban wooded hectare.
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Transmission of atmospherically deposited trace elements through an undeveloped, forested Maryland watershed
Retention and transmission of atmospherically-derived major (H + , Na + , K + , Ca 2+ , Mg 2+ , HCO 3 - , NO 3 - , SO 4 -2 , Cl - , SiO 2 ) and trace (Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se, and Zn) species were evaluated in an undeveloped forested watershed underlain by a rather inert quartzite lithology (Bear Branch, Catoctin State Forest, Thrumont, Maryland). These comparisons were based on atmospheric input to stream export over a period of 16 months. Both wet (precipitation) and total (bulk, including vegetative throughfall) atmospheric loading to the catchment were determined. Stream export was gauged based on systematic sampling of the stream under varied flow regimes. Additionally, watershed export of both dissolved and particulate trace element phases was examined during three high run-off intensives associated with summer storms.
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Spatial and temporal heterogeneity in metallic elements in industrialized aquatic bird habitat
This study examined the potential for exposure of migratory aquatic birds to contaminants in highly industrialized habitats at Baltimore Harbor, Maryland. Seven nearshore, benthic sites were sampled every 3 or 6 months from June 1987 to December 1988. Twenty metallic elements were measured in composites (i.e. annelids, amphipods, and isopods were pooled), clams, and sediments. Elevated concentrations were widespread throughout the sites, depending on the element. Most concentrations in composites were lowest at sites innermost and outside the harbor. Higher concentrations in composites were not related to season. Most concentrations were higher in composites than in sediments or clams, but they varied by element for clams and sediments. The largest flock of wintering waterfowl frequented the site exhibiting the highest concentrations of most elements ( p < 0.0001). Average concentrations of known toxic elements were probably not harmful to aquatic birds or their prey, but the highest detected concentrations of eight elements warrant caution. At least eight other elements exceeded background concentrations, but toxicity to birds or their prey are unknown.
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