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Richard G. Petersen

Publications and source records attributed to Richard G. Petersen.

9 recordsLinked to original sources
USGS1995

Evidence of autumn nitrogen limitation and contribution of picoplankton to carbon fixation in Lake Tahoe

Water samples were collected from Lake Tahoe at midlake and nearshore stations at three depths (25, 50, and 75 m, corresponding to light intensities of approximately 10, 1, and 0.1% of surface light) in May and September. The water samples were evaluated to decide the following: (1) whether carbon fixation was N-limited and whether there were differences between picoplankton and larger phytoplankters and (2) the relative importance of picoplankton carbon fixation and related photosynthetic parameters. Evidence of N-limitation was observed only in September at the midlake station for the populations at 50 and 75 m, and to a lesser extent at the nearshore station at 75 m, but only for the nanoplankton fraction. The contribution of picoplankton to total carbon fixation ranged from 34 to 69% and did not increase with depth. Low values for I k , the photoadaptation parameter, for deep water populations (0.1% light level) in September, but not May, suggested that these populations were adapted to low light in the fall but not the spring.

California, Nevada↗
USGS1970

Flood of March 1968 on the Sudbury, Assabet, and Concord Rivers, Massachusetts

During a 3-day period from March 17 to 19, 1968, a total of 3 to 7 inches of rain fell on parts of eastern Massachusetts. This heavy rainfall, combined with the generally wet antecedent conditions of the spring season and some runoff from snowmelt, caused considerable flooding of the rivers in the area. Property damage in Massachusetts from the flood was reported by the New England Division, Corps of Engineers (1968) to be $28 million. Most of the damage occurred where construction, both industrial and domestic, had encroached upon the flood plains of the rivers. The Sudbury and Assabet Rivers join at Concord, Mass., to form the Concord River (see fig. 1). This three-river system, which is known locally as the “SuAs-Co’’ basin, drains an area of about 405 square miles. The purpose of this report, which is one of a series covering the major flooded rivers in eastern Massachusetts, is to show flood stages and areas inundated by the March 1968 flood, to compare the severity of this flood with past floods, and to show the frequency of floods of given magnitudes which may be expected in the future at gaging stations in the basins. These basic flood data, as compiled, will serve as a broad, sound basis to assist state and local planners in such measures as flood-plain zoning and flood containment and prevention.

Massachusetts↗
USGS1960

Deposits of the manganese oxides

One of the problems of the wartime program of studies of domestic manganese deposits concerned the identification of, and modes of origin of the manganese oxide minerals. Of the hundreds of specimens of the oxides collected in the United States, the minerals of about 250 specimens were identified by X-ray analysis; complete chemical analyses were made of about 35 specimens and partial analyses of about 150 specimens. This report presents the conclusions that arise out of a review of the geologic environment under which the specimens were found. One conclusion of this review concerns the supergene vs. hypogene origin of the oxides. In order to reach conclusions concerning the supergene and hypogene origin of the 33 oxides of manganese recognized thus far, it was necessary to define the criteria that seemed usable.One group of oxides appears to be persistently supergene: groutite, hydrohausmannite, lithiophorite, rancieite, hetaerolite, hydrohetaerolite, chalcophanite, crednerite, woodruffite, and wad. Another group of oxides appears to have been formed only by hypogene processes: manganosite, hausmannite, pyrochroite, bixbyite, galaxite, jacobsite, franklinite, pyrophanite, and ilmenite. A third group of oxides appear to have been formed by supergene processes in some places and by hypogene processes in other places: manganite, pyrolusite, ramsdellite, cryptomelane, psilomelane, hollandite, braunite, and coronadite.Another conclusion concerns a genetic relation between: (1) veins of manganese oxides in the southwest, largely in Tertiary volcanic rocks, (2) bodies of oxides in travertine aprons near active hot springs, and inactive Pleistocene springs, and (3) stratified oxides, largely in late Tertiary sedimentary rocks in the southwest. From the features of these three groups of deposits of oxides and their geologic and geographic distribution, it appears that hot water from great depth rose on fractures in areas of volcanic activity, deposited oxides in the fractures, appeared at the surface as hot springs, deposited oxides in the aprons near the springs and continuing to local basins, deposited manganese oxides with local debris as persistent beds in sediments, partly or wholly of volcanic origin.

Economic Geology↗