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Geology topics

Research about Virginia

Source-linked reports with geographic coverage including Virginia.

At least 595 records · Page 33Linked to original sources
USGS1963

Hydraulic geometry of a small tidal estuary

A tidal channel in a marsh bordering the Potomac River near Alexandria, Va., was mapped, and current-meter measurements of discharge were made at various locations and at various stages in the tidal cycle. These measurements allowed analysis of the change of width, depth, and velocity with discharge at various cross sections and along the length of the channel. There is also presented a theoretical development of some, of these same relations based on hydraulic principles and on the assumption of a uniform distribution of energy and a minimum rate of work in the system as a whole. The change of width, depth, and velocity with discharge downstream developed from the field data checked closely with the theoretically derived values. The estuarine channel differs from a terrestrial one in that discharge at any section in an estuary varies depending on how the flow shaped the entire length of the channel between the point in question and the main body of tidal water. The result is that a tidal channel changes more rapidly in width and less rapidly in depth as discharge changes downstream than does a terrestrial channel.

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USGS1961

The trout fishery in Shenandoah National Park

Populations of brook trout in streams of Shenandoah National Park were reduced drastically early in the past decade by a succession of unusually severe droughts and floods. The drying of stream beds, predation, and scouring were principal factors in the loss of fish. The park was closed to fishing in 1954 and 1955 to protect survivors. The small numbers of survivors quickly repopulated the streams after drought conditions abated. The stocking of hatchery-reared fingerling trout in selected waters failed to augment the recovery of populations. Survival and growth of young, wild trout were especially good. Their redistribution through miles of previously dry streams was rapid. The park was opened again to fishing in 1956 under regulations which restrict the take but afford an increase in sporting opportunity. Two streams were placed under fishing-for-fun-only regulations in 1961. The welfare of the trout populations is dependent mostly on the weather cycle . Fish may be abundant in wet years but very scarc e in dry ones. Thus, the stream must be managed a s marginal for trout.

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USGS1960

Geomorphology and forest ecology of a mountain region in the central Appalachians

The area studied, mostly in the headwaters of the Shenandoah River, Augusta and Rockingham Counties, Va., includes about 55 square miles of densely forested mountain land and has an average relief of about 1,500 feet. It is part of an area that in June 1949 was subjected to a violent cloudburst which damaged large tracts on slopes and bottom lands. Most of the area is underlain by flaggy arkosic sandstone and interbedded reddish shale of the Hampshire formation of Devonian age. The highest ridges are capped by massive sandstone of the Pocono formation of Mississippian age. In most of the area the rocks dip gently to the southeast but in the northwestern and southeastern parts they are folded into synclines that localize northeastward-trending ridges.

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USGS1958

Minerals of the cassiterite-bearing veins at Irish Creek, Virginia, and their paragenetic relations

Major rock types of the Irish Creek district are gneisses and schists, intruded by granodiorite. All these rocks are believed to be Precambrian. The ore deposits are fissure veins consisting largely of quartz veins bordered by greisen, and enriched by recurrent deposition. From field and microscopic evidence six stages of mineral formation have been deduced: 1. Crystallization of the granodiorite with the formation of hypersthene, augite, hornblende, andesine, orthoclase, microcline, and quartz; and accessory apatite, rutile, ilmenite, titanomagnetite, and zircon. 2. Metamorphism of the granodiorite and gneiss with formation of uralitic actinolite, epidote, and sphene. 3. A period of fracturing and formation of quartz veins. 4. Greisenization of the host rock producing first: coarse muscovite, brown biotite, cassiterite, beryl, wolframite, and quartz; then producing a second group of minerals-fluorite, green biotite, chlorite, phenakite, siderite, ankerite, parisite, sphalerite, sulfides, including aikinite and galeno-bismutite, leucoxene, fine muscovite, and quartz. 5. Formation of late vein minerals, clinozoisite, calcite, nontronite, and montmorillonite. 6. Formation of surficial alteration products, kaolinite, vermiculite, hematite, limonite, and scorodite. The italicized mineral names indicate the minerals heretofore unreported from Irish Creek; parisite, aikinite, and galenobismutite are new minerals for Virginia. Included in the detailed descriptions of all the minerals is a chemical analysis of beryl.

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USGS1955

Catoctin formation near Luray, Virginia

In the Blue Ridge Province of northern Virginia, Maryland, and southern Pennsylvania the established lower Cambrian beds are underlain by a thick sequence of greenstone and interbedded sedimentary rocks known as the Catoctin formation. In an effort to determine the thickness of the formation, its relationship to overlying and underlying rocks, and the original nature of the lavas from which the Catoctin greenstone was derived, an area near Luray, Virginia, was studied. There the Catoctin formation lies unconformably on granitic rocks. Its basal sedimentary layer ranges from a few inches to 150 feet thick and contains pebbles of underlying plutonic rocks. The erosion surface beneath the Catoctin is irregular, and in several places hills up to 750 feet high were buried beneath the Catoctin lavas. No important time break is indicated between the deposition of the Catoctin formation and of the overlying Cambrian sediments, and the Catoctin may be early Cambrian. Mineralogy, chemical composition, and primary structures indicate that the original Catoctin lavas were basaltic in composition and were probably normal plateau basalts. Columnar joints, amygdules, sedimentary dikes, flow breccias, low-dipping primary joints, and other primary structures are well preserved, and the flows in this area are believed to have been subaerial.

Virginia↗
USGS1955

Fossils from bore holes on the Eastern Shore Peninsula, Virginia

This report lists Foraminifera, Mollusca, and Ostracoda in five bore holes that penetrated a maximum of 445 feet of section in sediments of Pleistocene and Miocene age, and discusses the paleoecologic and stratigraphic significance of the fossils. It includes the contents of references 6, 16, and 18 of Virginia Division of Geology Mineral Resources Circular No. 2, dealing with the geology and groundwater resources of the Eastern Shore peninsula.

Virginia↗
USGS1955

Detailed logs of 28 wildcat wells in Lee, Wise, Buchanan, Montgomery, and Dickenson Counties, Virginia

The Clinchfield Coal Company No. 102 well was drilled in the western part of Buchanan County near the Dickinson County line. The well started in the Pennsylvanian Norton formation and originally stopped in the Big Stone Gap shale. It was later deepened during 1950 to a total depth of 5847 but the samples from the deepened hole were not available for study when this report was prepared. The Clinchfield Coal Company kindly made available for study and publication the samples from the surface to a depth of 4508 feet.

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