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W.A. White

Publications and source records attributed to W.A. White.

8 recordsLinked to original sources
USGS2024

Fluoride content of clay minerals and argillaceous earth materials

A reliable method, utilizing a fluoride ion-selective electrode, is described for the determination of fluoride in clays and shales. Interference by aluminum and iron is minimal. The reproducibility of the method is about ±5% at different levels of fluoride concentration. Data are presented for various clay minerals and for the <2-µm fractions of marine and nonmarine clays and shales. Fluoride values range from 44 ppm (0.0044%) for nontronite from Colfax, WA, to 51,800 ppm (5.18%) for hectorite from Hector, CA. In general, clays formed under hydrothermal conditions are relatively high in fluoride content, provided the hydrothermal waters are high in fluoride content. Besides hectorite, dickite from Ouray, CO, was found to contain more than 50 times as much fluoride (6700 ppm) as highly crystalline geode kaolinite (125 ppm). The clay stratum immediately overlying a fluorite mineralized zone in southern Illinois was found to have a higher fluoride content than the same stratum in a nonmineralized zone approximately 1 mile away. Nonmarine shales in contact with Australian coals were found to be lower in fluoride content than were marine shales in contact with Illinois coals. It is believed that, in certain instances, peak shifts on DTA curves of similar clay minerals are the result of significant differences in their fluoride content.

Clays and Clay Minerals↗
USGS2003

Holocene evolution of the western Orinoco Delta, Venezuela

The pristine nature of the Orinoco Delta of eastern Venezuela provides unique opportunities to study the geologic processes and environments of a major tropical delta. Remote-sensing images, shallow cores, and radiocarbon-dating of organic remains form the basis for describing deltaic environments and interpreting the Holocene history of the delta. The Orinoco Delta can be subdivided into two major sectors. The southeast sector is dominated by the Rio Grande-the principal distributary-and complex networks of anastomosing fluvial and tidal channels. The abundance of siliciclastic deposits suggests that fluvial processes such as over-bank flooding strongly influence this part of the delta. In contrast, the northwest sector is represented by few major distributaries, and overbank sedimentation is less widespread relative to the southeast sector. Peat is abundant and occurs in herbaceous and forested swamps that are individually up to 200 km2 in area. Northwest-directed littoral currents transport large volumes of suspended sediment and produce prominent mudcapes along the northwest coast. Mapping of surface sediments, vegetation, and major landforms identified four principal geomorphic systems within the western delta plain: (1) distributary channels, (2) interdistributary flood basins, (3) fluvial-marine transitional environments, and (4) marine-influenced coastal environments. Coring and radiocarbon dating of deltaic deposits show that the northern delta shoreline has prograded 20-30 km during the late Holocene sea-level highstand. Progradation has been accomplished by a combination of distributary avulsion and mudcape progradation. This style of deltaic progradation differs markedly from other deltas such as the Mississippi where distributary avulsion leads to coastal land loss, rather than shoreline progradation. The key difference is that the Orinoco Delta coastal zone receives prodigious amounts of sediment from northwest-moving littoral currents that transport sediment from as far away as the Amazon system (???1600 km). Late Holocene progradation of the delta has decreased delta-plain gradients, increased water levels, and minimized over-bank flooding and siliciclastic sedimentation in the northwest sector. These conditions, coupled with large amounts of direct precipitation, have led to widespread peat accumulation in interdistributary basins. Because peat-forming environments cover up to 5000 km2 of the delta plain, the Orinoco may be an excellent analogue for interpreting ancient deltaic peat deposits.

Geological Society of America Bulletin↗
USGS2002

A comparison of factors controlling sedimentation rates and wetland loss in fluvial-deltaic systems, Texas Gulf coast

Submergence of coastal marshes in areas where rates of relative sea-level rise exceed rates of marsh sedimentation, or vertical accretion, is a global problem that requires detailed examination of the principal processes that establish, maintain, and degrade these biologically productive environments. Using a simple 210Pb-dating model, we measured sedimentation rates in cores from the Trinity, Lavaca-Navidad, and Nueces bayhead fluvial-deltaic systems in Texas where more than 2000 ha of wetlands have been lost since the 1950s. Long-term average rates of fluvial-deltaic aggradation decrease southwestward from 0.514 ?? 0.008 cm year -1 in the Trinity, 0.328 ?? 0.022 cm year -1 in the Lavaca-Navidad, to 0.262 ?? 0.034 cm year -1 in the Nucces. The relative magnitudes of sedimentation and wetland loss correlate with several parameters that define the differing fluvial-deltaic settings, including size of coastal drainage basin, average annual rainfall, suspended sediment load, thickness of Holocene mud in the valley fill, and rates of relative sea-level rise. There is some evidence that upstream reservoirs have reduced wetland sedimentation rates, which are now about one-half the local rates of relative sea-level rise. The extant conditions indicate that fluvial-deltaic marshes in these valleys will continue to be lost as a result of submergence and erosion. ?? 2002 Elsevier Science B.V. All rights reserved.

Geomorphology↗
USGS2002

Regional controls on geomorphology, hydrology, and ecosystem integrity in the Orinoco Delta, Venezuela

Interacting river discharge, tidal oscillation, and tropical rainfall across the 22,000 km2 Orinoco delta plain support diverse fresh and brackish water ecosystems. To develop environmental baseline information for this largely unpopulated region, we evaluate major coastal plain, shallow marine, and river systems of northeastern South America, which serves to identify principal sources and controls of water and sediment flow into, through, and out of the Orinoco Delta. The regional analysis includes a summary of the geology, hydrodynamics, sediment dynamics, and geomorphic characteristics of the Orinoco drainage basin, river, and delta system. Because the Amazon River is a major source of sediment deposited along the Orinoco coast, we summarize Amazon water and sediment input to the northeastern South American littoral zone. We investigate sediment dynamics and geomorphology of the Guiana coast, where marine processes and Holocene history are similar to the Orinoco coast. Major factors controlling Orinoco Delta water and sediment dynamics include the pronounced annual flood discharge; the uneven distribution of water and sediment discharge across the delta plain; discharge of large volumes of water with low sediment concentrations through the Rio Grande and Araguao distributaries; water and sediment dynamics associated with the Guayana littoral current along the northeastern South American coast; inflow of large volumes of Amazon sediment to the Orinoco coast; development of a fresh water plume seaward of Boca Grande; disruption of the Guayana Current by Trinidad, Boca de Serpientes, and Gulf of Paria; and the constriction at Boca de Serpientes. ?? 2002 Elsevier Science B.V. All rights reserved.

Geomorphology↗
USGS2001

Mud volcanoes of the Orinoco Delta, Eastern Venezuela

Mud volcanoes along the northwest margin of the Orinoco Delta are part of a regional belt of soft sediment deformation and diapirism that formed in response to rapid foredeep sedimentation and subsequent tectonic compression along the Caribbean-South American plate boundary. Field studies of five mud volcanoes show that such structures consist of a central mound covered by active and inactive vents. Inactive vents and mud flows are densely vegetated, whereas active vents are sparsely vegetated. Four out of the five mud volcanoes studied are currently active. Orinoco mud flows consist of mud and clayey silt matrix surrounding lithic clasts of varying composition. Preliminary analysis suggests that the mud volcano sediment is derived from underlying Miocene and Pliocene strata. Hydrocarbon seeps are associated with several of the active mud volcanoes. Orinoco mud volcanoes overlie the crest of a mud-diapir-cored anticline located along the axis of the Eastern Venezuelan Basin. Faulting along the flank of the Pedernales mud volcano suggests that fluidized sediment and hydrocarbons migrate to the surface along faults produced by tensional stresses along the crest of the anticline. Orinoco mud volcanoes highlight the proximity of this major delta to an active plate margin and the importance of tectonic influences on its development. Evaluation of the Orinoco Delta mud volcanoes and those elsewhere indicates that these features are important indicators of compressional tectonism along deformation fronts of plate margins. ?? 2001 Elsevier Science B.V. All rights reserved.

Geomorphology↗
USGS2000

Rates of sediment supply and sea-level rise in a large coastal lagoon

Laguna Madre, Texas, is 3-7 km wide and more than 190 km long, making it one of the longest lagoons in the world. The lagoon encompasses diverse geologic and climatic regions and it is an efficient sediment trap that accumulates clastic sediments from upland, interior, and oceanic sources. The semi-arid climate and frequent tropical cyclones historically have been responsible for the greatest volume of sediment influx. On an average annual basis, eolian transport, tidal exchange, storm washover, mainland runoff, interior shore erosion, and authigenic mineral production introduce approximately one million m 3 of sediments into the lagoon. Analyses of these sediment transport mechanisms and associated line sources and point sources of sediment provide a basis for: (1) estimating the long-term average annual sediment supply to a large lagoon; (2) calculating the average net sedimentation rate; (3) comparing introduced sediment volumes and associated aggradation rates with observed relative sea-level change; and (4) predicting future conditions of the lagoon. This comparison indicates that the historical average annual accumulation rate in Laguna Madre (<1 mm/yr) is substantially less than the historical rate of relative sea-level rise (~4 mm/yr). Lagoon submergence coupled with erosion of the western shore indicates that Laguna Madre is being submerged slowly and migrating westward rather than filling, as some have suggested.

Marine Geology↗
USGS2000

Drainage-basis-scale geomorphic analysis to determine refernce conditions for ecologic restoration-Kissimmee River, Florida

Major controls on the retention, distribution, and discharge of surface water in the historic (precanal) Kissimmee drainage basin and river were investigated to determine reference conditions for ecosystem restoration. Precanal Kissimmee drainage-basin hydrology was largely controlled by landforms derived from relict, coastal ridge, lagoon, and shallow-shelf features; widespread carbonate solution depressions; and a poorly developed fluvial drainage network. Prior to channelization for flood control, the Kissimmee River was a very low gradient, moderately meandering river that flowed from Lake Kissimmee to Lake Okeechobee through the lower drainage basin. We infer that during normal wet seasons, river discharge rapidly exceeded Lake Okeechobee outflow capacity, and excess surface water backed up into the low-gradient Kissimmee River. This backwater effect induced bankfull and peak discharge early in the flood cycle and transformed the flood plain into a shallow aquatic system with both lacustrine and riverine characteristics. The large volumes of surface water retained in the lakes and wetlands of the upper basin maintained overbank flow conditions for several months after peak discharge. Analysis indicates that most of the geomorphic work on the channel and flood plain occurred during the frequently recurring extended periods of overbank discharge and that discharge volume may have been significant in determining channel dimensions. Comparison of hydrogeomorphic relationships with other river systems identified links between geomorphology and hydrology of the precanal Kissimmee River. However, drainage-basin and hydraulic geometry models derived solely from general populations of river systems may produce spurious reference conditions for restoration design criteria.

Florida↗