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Cyclic Aggradation and Downcutting, Fluvial Response to Volcanic Activity, and Calibration of Soil-Carbonate Stages in the Western Grand Canyon, Arizona (2000)

Lucchitta, Ivo ; Curtis, Garniss H. ; Davis, Marie E. ; [weitere]

Cambridge University Press

In: Quaternary Research. 2000; 53(1): 23-33. Published 2000 Jan 01. doi: 10.1006/qres.1999.2098.

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Publikationsdatum: 2000-01-01

Beschreibung: In the western Grand Canyon, fluvial terraces and pediment surfaces, both associated with a Pleistocene basalt flow, document Quaternary aggradation and downcutting by the Colorado River, illuminate the river's response to overload and the end of overload, and allow calibration of soil-carbonate stages and determination of downcutting rates. Four downcutting–aggradation cycles are present. Each begins with erosion of older deposits to form a new river channel in which a characteristic suite of deposits is laid down. The current cycle (I) started ∼700 yr B.P. The oldest (IV) includes the 603,000 ± 8000 to 524,000 ± 7000 yr Black Ledge basalt flow, emplaced when the river channel was ∼30 m higher than it is now. The flow is overlain by basalt–cobble gravel and basalt sand. Soils reach the stage V level of carbonate development. Calibrated ages for soil stages are Stage V, ∼525,000 yr; stage IV,

Print ISSN: 0033-5894

Digitale ISSN: 1096-0287

Thema: Geographie , Geologie und Paläontologie

Publiziert von Cambridge University Press

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A microcontroller-based data-logger design for seasonal hydrochemical studies (2001)

Davis, Jerry D. ; Davis, Glenn A.

Wiley

In: Earth Surface Processes and Landforms. 2001; 26(10): 1151-1159. Published 2001 Jan 01. doi: 10.1002/esp.262.

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Publikationsdatum: 2001-01-01

Print ISSN: 0197-9337

Digitale ISSN: 1096-9837

Thema: Geographie , Geologie und Paläontologie

Publiziert von Wiley im Namen von British Society for Geomorphology.

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Digitale Medien

Parameter estimation in low order fractionally differenced ARMA processes (1989)

Boes, D. C. ; Davis, R. A. ; Gupta, S. N.

Springer

Stochastic environmental research and risk assessment 3 (1989), S. 97-110

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ISSN: 1436-3259

Schlagwort(e): ARMA processes ; fractionally differencedARMA processes ; long memory ; spectral density ; maximum likelihood estimates

Quelle: Springer Online Journal Archives 1860-2000

Thema: Architektur, Bauingenieurwesen, Vermessung , Energietechnik , Geographie , Geologie und Paläontologie

Notizen: Abstract A class of regression type estimators of the parameterd in a fractionally differencedARMA (p, q) process is introduced. This class is an extension of the estimator considered by Geweke and Porter-Hudak. In a simulation study, we compared three estimators from this class together with two approximate maximum likelihood estimators which are based on two separate approximations to the likelihood. One approximation ignores the determinant term in the likelihood and the other includes a compensating factor for the determinant. When the determinant term is included, the estimate tends to be much less biased and is in general superior to the other estimate. The approximate maximum likelihood estimator out performed, by a large margin, the regression type estimators for pureARIMA (0,d,0) processes. However, forARIMA (1,d,1) processes, a regression type estimator turned out to be the best for realizations of length 400 in 3 out of the 5 cases we tried.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01544075

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