Appalachenprofil 1964

Our knowledge of the Appalachians has grown very satisfoctorily during the last ten years. Folding took place at least twice: 1. In the Ordovician the basement including the crystalline axis as far as the Blue Ridge became consolidated. This region became highland and furnished the material for upper Ordovician to Carboniferous sediments. This has been established by three methods: first, facies examinations; second,Pettijohn and his students found that sediments were transported from East to West during the upper Ordovician, Silurian, Devonian, and Carboniferous periods; and finallyHopson has summarized absolute age determinations which show that the basement, (Cambrian, and lower Ordovician rocks included) were consolidated and uplifted about 440 million years ago. Thus, in the first period of folding the Blue Ridge Zone, which is the western margin of the basement complex, was uplifted and crowded westward. Cambrian and Ordovician sediments which cover the basement as a thin layer were folded simultaneously. Folding intensity decreases from East to West and regional cleavage and lineation disappear at the “tectonite Front”. 2. The upper part of the Paleozoic column was folded during Appalachian orogeny presumably near the surface and with little or no influence by the basement. Maybe both the Foreland and the folded Appalachians “crept” over the basement forming sharply marked anticlinal axes and broad synclinal troughs. However,Cooper supposes that the basement took part through vertical movements and in this way was partly responsible for sedimentation and possibly also for structures. In the Maryland profile lateral reduction is less than further south where folds grade into nappe-like overthrusts and the foothill folds disappear below great horizontal thrusts.     

Deformation microstructures in experimentally deformed Maryland diabase

Experimentally deformed Maryland diabase has been examined using the transmission electron microscope in order to determine the mechanisms of deformation operative over a range of temperatures and pressures and thereby aid in the interpretation of polyphase flow data. Deformation mechanisms within the plagioclase and clinopyroxene of the diabase have been compared to those within monomineralic aggregates of these phases deformed at the same conditions. Both phases deform by microfracturing, mechanical twinning, and intracrystalline slip.Data for the monomineralic aggregates show that plagioclase is stronger than clinopyroxene at <800°C, but weaker at ≥ 800°C, for a pressure of 15 kbar and strain rate of 10^?6/sec. Observations of the diabase are consistent with this result: at < 800°C, the plagioclase and pyroxene grains are about equally strained, whereas at ≥ 800°C, almost all of the sample strain is accommodated by the plagioclase, the more continuous phase.     

Regional levels of indoor radon in Virginia and Maryland

The levels of Rn-222 in homes located in Fairfax County, Virginia, and Montgomery County, Maryland, are currently being measured during four consecutive three-month seasonal intervals using alpha-track detectors. Significant variations occur between parts of northern Virginia and southern Maryland because the area is part of three very different geologic provinces. Results from the winter period in these three provinces show that the indoor radon levels were about twice as high as anticipated. Approximately 45 percent of the homes had winter indoor radon levels above 4 pCi/l, the EPA’s recommended action level, and in the spring period, more than 30 percent of the homes still had indoor levels above 4 pCi/l. Indoor radon variations due to seasonal control were about as significant as geological control. Worst-case combinations developed over some rock units in the winter, producing areas in which about 70 percent of the homes exceeded 4 pCi/l.     

The use of pump-out facilities by recreational boaters in Maryland

Because of the intense interest in the water quality of the Chesapeake Bay, the State of Maryland sponsored a survey of 500 Maryland boaters to determine their use of marina facilities to discharge sewage from portable toilets or holding tanks. We report results of that survey as well as examine some of the factors that contribute to the use of pump-out facilities. Presently, with under 10% of Maryland’s marinas having facilities available to pump out holding tanks or portable toilets, less than one in twenty boaters has ever used such a facility. Moreover, less than one in three boats equipped with holding tanks or portable toilets has ever used such a facility. Using a discrete choice behavioral model, we found that boaters with portable toilets were more likely to use facilities than ones with holding tanks, especially if the holding tanks were equipped with macerating devices. The price of using the pump-out facility negatively influenced pump-out use. We also found that vessels in transition were less likely to use marina facilities. Finally, the availability of a pump-out facility at a boater’s marina increased the likelihood of pumping by twofold. In Maryland reduction of boat-generated pollution will likely require a policy of both extensive pump-out services and low costs for the services.     

Seasonal Factors Influencing Copepod Abundance in the Maryland Coastal Bays

Maryland Coastal Bays differ in hydrography from river-dominated estuaries because of limited freshwater inflow from tributary creeks and more marine influence. Consequently, the copepod community structure may be different from that of the coastal ocean and river-dominated estuaries in the mid-Atlantic region. A 2-year study was conducted to describe copepod species composition and seasonal patterns in abundance and factors influencing the community structure. Seven copepod genera, Acartia, Centropages, Pseudodiaptomus, Parvocalanus, Eurytemora, Oithona, and Temora, in addition to harpacticoids were found. The copepod community was dominated by Acartia spp. (64%), followed by Centropages spp. (30%), unlike in river-dominated estuaries in the region where the copepod community is usually dominated by Acartia spp. followed by Eurytemora affinis. Acartia tonsa was the most abundant in summer and fall whereas Centropages spp., Temora sp., Oithona similis, E. affinis, and harpacticoids were most abundant in winter and early spring. Parvocalanus crassirostris and Pseudodiaptomus pelagicus were present in fall and winter but at relatively low densities. The highest mean density of copepods occurred in winter 2012 (36,437 m^?3) and the lowest in spring 2013 (347 m^?3). Low densities occurred through early summer (614 m^?3) coinciding with peak spawning by bay anchovy (Anchoa mitchilli). Bottom-up control via low phytoplankton biomass coupled with top-down control by ctenophores (Mnemiopsis sp.), mysids (Neomysis americana), and bay anchovy was probably responsible for the low copepod densities in spring and early summer. Temperature and salinity were also important factors that influenced the seasonal patterns of copepod species occurrence. The observed seasonal differences in the abundance of copepods have important implications for planktivorous fishes as they may experience lower growth rates and survival due to food limitation in spring/early summer when copepod densities are relatively low than in late summer/fall when copepod abundance is higher.     

Osprey reproductive success along Choptank River,Maryland

Reproductive success was determined for 275 osprey nesting attempts along the Choptank River, Maryland in 1972–79. Young were fledged from 64% of the nests, and 1.25 young fledged per occupied nest. This level of reproductive success was above that found in the same area in 1968–71, better than that observed in other portions of the United States including most other Chesapeake Bay tributaries, and within the estimate necessary for population stability. Human disturbance and environmental pollution reduced reproductive success.     

Dynamic analysis of rough cleavage in the Martinsburg Formation,Maryland

Deformation lamellae in detrital quartz and twin lamellae in vein calcite are common in greywacke beds in the upper portion of the Martinsburg Formation near Williamsport, Maryland. These features are a product of the same stresses that resulted in the formation of rough cleavage. Dynamic analysis of the deformation lamellae and the calcite twins indicates that the cleavage formed normal to the maximum principal stress. In limb samples, the intermediate principal stress is parallel to the fold axis and the least principal stress plunges steeply in the cleavage plane. In most hinge samples the intermediate and least stress axes could not be differentiated and together define the cleavage plane. The lamellae developed during a period of high differential stress that accompanied flattening of early-formed buckle folds. The abundance of deformation lamellae and their development synchronous with the cleavage, demonstrates that intracrystalline deformation may be an important mechanism in the formation of rough cleavage.     

Multi-scale characterization of swelling behaviour of compacted Maryland clay

This paper presents a comprehensive experimental investigation on time-dependent swelling behaviour at both macroscale and microscale of a natural Australian expansive soil in compacted state. A number of one-dimensional swelling tests under different vertical pressures, different initial void ratios and initial water contents were performed. The characterization at macroscale was complemented by extensive microstructural investigations through mercury intrusion porosimetry and scanning electron microscope observation on both as-compacted and swollen specimens. The results were discussed at two different scales within a framework of double-porosity, which was finalized by linking the macrostructural–microstructural strains ratio with secondary swelling/compression coefficients. The multi-scale correlation appears to be largely independent of the specimen initial conditions. The study showed that the secondary swelling and primary swelling are governed by the same factors and that secondary swelling takes place mainly in macropores, of which the change magnitude depends on the level of confinement applied. The microstructural investigations show that swelling is accompanied by significant microfabric changes.     

Nutrient Budgets and Management Actions in the Patuxent River Estuary,Maryland

Multi-year nitrogen (N) and phosphorus (P) budgets were developed for the Patuxent River estuary, a seasonally stratified and moderately eutrophic tributary of Chesapeake Bay. Major inputs (point, diffuse, septic, and direct atmospheric) were measured for 13 years during which, large reductions in P and then lesser reductions in N-loading occurred due to wastewater treatment plant improvements. Internal nutrient losses (denitrification and long-term burial of particulate N and P) were measured in tidal marshes and sub-tidal sediments throughout the estuary as were nutrient storage in the water column, sediments, and biota. Nutrient transport between the oligohaline and mesohaline zones and between the Patuxent and Chesapeake Bay was estimated using a salt and water balance model. Several major nutrient recycling terms were directly and indirectly evaluated and compared to new N and P inputs on seasonal and annual time-scales. Major findings included: (1) average terrestrial and atmospheric inputs of N and P were very close to the sum of internal losses plus export, suggesting that dominant processes are captured in these budgets; (2) both N and P export were a small fraction (13% and 28%, respectively) of inputs, about half of that expected for N based on water residence times, and almost all exported N and P were in organic forms; (3) the tidal marsh-oligohaline estuary, which by area comprised ~27% of the full estuarine system, removed about 46% and 74% of total annual upland N and P inputs, respectively; (4) recycled N and P were much larger sources of inorganic nutrients than new inputs during warm seasons and were similar in magnitude even during cold seasons; (5) there was clear evidence that major estuarine processes responded rapidly to inter-annual nutrient input variations; (6) historical nutrient input data and nutrient budget data from drought periods indicated that diffuse nutrient sources were dominant and that N loads need to be reduced by about 50% to restore water quality conditions to pre-eutrophic levels.     

Fabric at granodiorite-schist contact,Bear Island,Maryland

Summary The essential difference between the granodiorite and its wall rock fabric consists in the two well-defined deformation plans. The wall rock is a B-tectonite, the granodiorite an S-tectonite. Transport in the former was rotational and monoclinic, in the latter possibly by laminar flow parallel with the contact.The granite fabric could hardly be an in place fabric or replacement without differential movement. It would have retained the wall rock fabric, even if not the mineral composition. Transport in the granodiorite was presumably along the wall parallel S₄ and the contact. The present study is barely a beginning, but it is hoped that it can be continued in the near future and extended over a wider area.With 9 figures.     

Statistical modeling of historic shore erosion rates on the Chesapeake Bay in Maryland

Few strong relationships exist along the Chesapeake Bay shoreline between the historic erosion rate and the distribution of any of several coastal parameters which were defined and tested using traditional regression and discriminant analysis procedures To develop a simple predictive equation for shore erosion that could be used by coastal managers, the entire Chesapeake Bay shoreline was partitioned into naturally occurring reaches 2–5 km in length, and the historic erosion rate on each reach was modelled as a function of five variables (a) shoreline type, (b) “100-year” storm surge height, (c) mean tide range, (d) wave climate, and (e) potential littoral drift rate The statistical analysis yielded a multiple correlation coefficient (r ²) of 30 8%, discriminant analysis showed only the first two variables listed above are useful predictors (i e, statistically significant) of historic erosion rates A 95-mile portion of the same bay shoreline in Queen Anne’s and Talbot counties was then partitioned into shorter reach lengths (1/2–2km) and more variables were included The multiple correlation coefficient (r ²) improved slightly to 32 9%, but only shoreline type and potential littoral drift rate were found to be useful predictors of historic erosion rates Curiously, the ability to model statistically the historic shore erosion rate is best on those reaches already substantially protected by structures For Queen Anne’s and Talbot counties, the multiple regression coefficient improved to 61 5% when only reaches 1/2–2km in length protected by structures were considered.     

Long-term Dynamics of Phytoplankton in the Rhode River,Maryland (USA)

We analyzed interannual variability in a long-term record of chlorophyll concentration and phytoplankton species composition in the Rhode River, Maryland (USA). Over the approximately 30-year record, there was no long-term monotonic trend in phytoplankton chlorophyll concentration, though temporary directional trends related to precipitation patterns sometimes persisted for a decade before reversing. From counts on preserved samples, we estimated the dominance by different pigment-bearing groups and size classes. Diatoms, dinoflagellates, and cryptophytes comprised about 80–97% of the annual averaged class-specific biovolume. Cryptophytes dominated the first 2 years in the data set but displayed a long-term decline, after which diatoms dominated in all but four consecutive years in which there were large dinoflagellate blooms. There was a long-term increase in cells with equivalent spherical diameters from 4 to 10 μm, accompanied by declines in the proportion of cells in the 2- to 4- and 10- to 20-μm size classes. The main cause of these changes in size classes was a long-term increase in Chroomonas sp. and Apedinella radians and long-term decline in Microcystis sp. and an unidentified cryptophyte, respectively. These taxa were cosmopolitan in their seasonal and spatial distributions, and hence the long-term changes in taxa did not conform well with conceptual models based on succession of “life-forms.” The segregation of diatoms and dinoflagellates expected on the basis of “life-forms” applied to seasonal and spatial patterns. Characterizing the phytoplankton community in terms of diversity, size, and class-specific biovolume gave results that were consistent with one another and added insight to the broad-scale changes in chlorophyll concentration. Subtle changes in the size distribution of cryptophytes were not apparent from biovolume measures and would not have been apparent without microscopy. Though causes of such shifts may be difficult to identify, identifying the causes and predicting potential consequences cannot even be attempted without awareness of the phenomena.     

Subtidal distribution of barnacles (Cirripedia: Balanidae) in Chesapeake Bay,Maryland

From 1977 to 1980, samples of barnacles were collected (as opportunities arose) from 61 subtidal locations (mostly oyster beds) around Chesapeake Bay, Maryland. Three species were identified from the area.Balanus improvisus dominated, comprising 83% of the 8,231 barnacles identified, and was collected at all locations but one. It occurred over a collection salinity range of 0.8‰ to 17.9‰.Balanus subalbidus (14% of the barnacles identified) was collected over the same salinity range, but mainly in lower salinity waters.Balanus eburneus was scarce (2% of the barnacles identified) and was collected at higher salinities (8.5‰ to 17.1‰).     

A revised species list and commentary on the macroalgae of the Chesapeake Bay in Maryland

Macroscopic marine algae were collected at a variety of intertidal sites and on cruises throughout the Maryland Chesapeake Bay in 1972–73, and numerous specimens from the University of Maryland herbarium were examined. The revised species list contains 62 taxa as follows: 26 Rhodophyceae, 1 Xanthophyceae, 6 Phaeophyceae, 29 Chlorophyceae. Grinnellia americana, Neoagardhiella baileyi, Porphyra sp.,Vaucheria sp.,Desmotrichum undulatum, Ectocarpus confervoides, Enteromorpha compressa var.lingulata, E. linza, Entocladia viridis andUrospora sp. are new records for the flora of the upper Bay. Records ofAscophyllum are believed to represent discarded bait-packing material rather than an endemic population in the upper Bay. Ceramium, Polysiphonia, Cladophora, Enteromorpha andUlva are the genera most likely to be encountered in the upper Bay. In winter, brown algae, mainlyEctocarpus species, become a more conspicuous component of the flora. Comments on distribution, seasonality, taxonomic problems, and invalid or questionable records are included. Literature pertinent to the Delmarva region is reviewed briefly.     

Temporal and spatial variations of trace metal concentrations in oysters from the Patuxent River, Maryland

Concentrations of copper (Cu), silver (Ag), and cadmium (Cd) in eastern oysters (Crassostrea virginica) from the upper Patuxent River estuary analyzed since 1986 (Cd since 1991) were high relative to concentrations in other sites in the United States analyzed by the National Oceanic and Atmospheric Administration National Status and Trends program. Patuxent River oysters had above average concentrations of Ag and Cu, and unusually high concentrations of Cd. Metal concentrations were highest in summer, a period in which oyster meat condition index was relatively low. Copper values were highest in 1986–1987, likely elevated by erosion from Cu-Ni alloy condensers at a local power plant. Silver and Cd values exhibited more year-to-year variation. A number of factors were examined as candidates to explain the interannual differences, including river flow, salinity, and oyster condition, but none was able to explain the high and low years. Samples collected in spring and late summer of 1996 at a number of oyster bars located along the length of the Patuxent River showed that concentrations of all three metals increased with distance up-river. For Cd, the upstream increase was linear with distance, while for Ag and Cu, there was a secondary maximum near river km 16. A close correlation was observed between Ag and Cu for individuals at each site, with a poorer correlation between Cd and either Ag or Cu.     

Influences of Wave Climate and Sea Level on Shoreline Erosion Rates in the Maryland Chesapeake Bay

We investigated spatial correlations between wave forcing, sea level fluctuations, and shoreline erosion in the Maryland Chesapeake Bay (CB), in an attempt to identify the most important relationships and their spatial patterns. We implemented the Simulating WAves Nearshore (SWAN) model and a parametric wave model from the USEPA Chesapeake Bay Program (CBP) to simulate wave climate in CB from 1985 to 2005. Calibrated sea level simulations from the CBP hydrodynamic model over the same time period were also acquired. The separate and joint statistics of waves and sea level were investigated for the entire CB. Spatial patterns of sea level during the high wave events most important for erosion were dominated by local north-south winds in the upper Bay and by remote coastal forcing in the lower Bay. We combined wave and sea level data sets with estimates of historical shoreline erosion rates and shoreline characteristics compiled by the State of Maryland at two different spatial resolutions to explore the factors affecting erosion. The results show that wave power is the most significant influence on erosion in the Maryland CB, but that many other local factors are also implicated. Marshy shorelines show a more homogeneous, approximately linear relationship between wave power and erosion rates, whereas bank shorelines are more complex. Marshy shorelines appear to erode faster than bank shorelines, for the same wave power and bank height. A new expression for the rate of shoreline erosion is proposed, building on previous work. The proposed new relationship expresses the mass rate of shoreline erosion as a locally linear function of the difference between applied wave power and a threshold wave power, multiplied by a structure function that depends on the ratio of water depth to bank height.     

Germination ecology of a Maryland population of saltmarsh bulrush (Scirpus robustus)

Germination and growth responses ofScirpus robustus Pursh were determined for a variety of environmental conditions. A period of after-repening was required for seed germination; the most effective pretreatment was chilling at 2 C. Alternate freezing and thawing, freezing, and warm dry storage resulted in lower germination. Scarification was effective in increasing seed germination. Low concentrations of salt depressed germination and growth. A definite light requirement was found, but photoperiod length had no effect on germination responses. Alternating temperatures promoted germination; the best overall response occurred with 35 C day/25 C night. Presence ofS. robustus within the marsh community is discussed in relation to germination and seedling establishment characteristics of the species.     

Hydrologic inferences from ring widths of flood-damaged trees,Potomac River,Maryland

Year-to-year variability in the ring widths of trees on flood plains along two reaches of the Potomac River near Washington, D.C., seems in large part to be related to differences in flood-flow regimes. Trees directly exposed to high flood velocities are damaged more often than sheltered trees and thus exhibit more variable ring-width patterns. The ring-width variability of unsheltered trees on low levels of flood plains is greater than that of trees on high levels, indicating that variability values are positively correlated with flood frequency. Sheltered trees, however, have less variable ring-width patterns than those of unsheltered trees, and variability is not correlated with flood frequency. As a result, ring-width variations may be used to estimate the probability of flood damage along local channel reaches of a stream. Growth responses after hydrologic catastrophies in 1948 and 1972 indicate that rings of flood-plain trees can be used to document the occurrence and crest altitude of high-magnitude floods.     

The ecological condition of dead-end canals of the Delaware and Maryland coastal bays

Manmade, dead-end canals are common in residential developments along the coastal bays of Delaware and Maryland. The close proximity of housing to the water and the concentration of boating activities enhances the potential for anthropogenic stress to living resources in these poorly flushed aquatic systems. Measurements of water quality, sediment contaminants, and benthic macroinvertebrate assemblages were taken in 25 randomly selected canals and compared to 175 non-canal sites located throughout the coastal bays. The mean bottom dissolved oxygen concentrations in canals was half that found in non-canal sites. Mean water-column and benthic chlorophyll concentrations were, respectively, two times and four times higher in the canals. Sediment contaminant concentrations were significantly higher in the canals compared to the coastal bays, and exceeded published guideline values indicating possible adverse ecological effects. The contaminants of greatest concern in the canals included arsenic, copper, polyaromatic hydrocarbons, polychlorinated biphenyls, and several banned, persistent pesticides (DDT, dieldrin, endrin, and chlordane). Benthic macroinvertebrate assemblages in canals were severely degraded; mean species richness, abundance, and biomass were 1/7, 1/10, and 1/20, respectively, of the values for the remaining coastal bays. A single pollution-tolerant polychaete species (Streblospio benedicti) comprised approximately three-fourths (70%) of the community in the canals. Deep (>1 m) and muddy canals were in poorer condition than shallow and sandy ones.