Estimation of Tigris-Euphrates streamflow from regional paleoenvironmental proxy data     

Paul A. Kay  Douglas L. Johnson 《Climatic change》1981,3(3):251-263

A six thousand year history of streamflow in Mesopotamia is derived from a synthesis of regional paleoenvironmental proxy data. The proxy data are interpreted with consideration to the climatic signals represented in the records and to the temporal resolution of the records. A consideration of modern synoptic climatology suggests the spatial patterns of streamflow-generating precipitation in relation to atmospheric circulation. These patterns provide a framework for the interpretation of streamflow from the regional proxies. Given the nature of the data at hand, only a low frequency signal is reconstructed. Assessment of the role of small scale climatic fluctuations as a forcing function of population dynamics must await the availability of finer resolution environmental data.  相似文献   

The seaward margin of belize barrier and atoll reefs: Special Publication No. 3 of the International Association of Sedimentologists. N.P. James and R.N. Ginsburg. Blackwell,Oxford, 1979, 191 pp., £10.00.     

Kenneth G. Johnson 《Sedimentary Geology》1981,30(3):243

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Experimental Determination of Thermoplastic Casing Collapse Pressures     

Roy C. Johnson  Jr.    Carl E. Kurt  George F. Dunham  Jr. 《Ground water》1980,18(4):346-350

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Hillslope stability and landslide hazard—a case study from Longdendale,north Derbyshire,England     

R.H. Johnson 《Proceedings of the Geologists' Association. Geologists' Association》1980,91(4):315-325

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Magma genesis in the New Britain island-arc: Constraints from Nd and Sr isotopes and trace-element patterns     

D. J. DePaolo  R. W. Johnson 《Contributions to Mineralogy and Petrology》1979,70(4):367-379

A selected suite of fresh volcanic rocks from the New Britain island arc has been analyzed for ¹⁴³Nd/¹⁴⁴Nd, ⁸⁷Sr/⁸⁶Sr, major and trace elements to investigate relationships between isotopes, trace elements and petrology, and depth to the underlying Benioff zone. From these relationships inferences about magma generation are made utilizing Nd and Sr isotope systematics in possible source materials. Lavas ranging in composition from basalt to rhyolite show minimal variation of ¹⁴³Nd/¹⁴⁴Nd. Small variations in ⁸⁷Sr/⁸⁶Sr do not correlate with depth to the Benioff zone, but are related to magma type. Nd-Sr isotopes suggest that island arc lavas in general are derived from a mixture of suboceanic mantle and hydrothermally altered mid-ocean ridge-type basalt, but the New Britain magma source appears homogeneous with little indication of either the involvement of oceanic crust or mantle inhomogeneity. Trace element patterns in New Britain lavas are not consistent with Nd isotope data for currently accepted petrologic and trace element models of magma genesis. Mafic lavas from New Britain and other island arcs have anomalously high Sr/Nd, possibly due to components derived from subducted oceanic crust.  相似文献   

REE-fractionated trachytes and dacites from Papua New Guinea and their relationship to andesite petrogenesis   总被引：1，自引：0，他引：1  

I. E. M. Smith  S. R. Taylor  R. W. Johnson 《Contributions to Mineralogy and Petrology》1979,69(3):227-233

Minor trachyte and dacite temporally associated with, but spatially separated from, arc-trench type volcanoes in Papua New Guinea have distinctive REE abundances similar to experimentally produced and theoretically predicted partial melts of eclogite. However, modelling based on small amounts of equilibrium partial melting indicates that only fractionation involving a garnet-dominated residuum can account for the observed REE patterns if the source rock was subducted oceanic basalt. If the source was geochemically evolved, other mineral phases (e.g., amphibole) are possible in the residuum, and there is no necessity to postulate that the downgoing slab was the source for these magmas. The REE fractionated trachytes and dacites appear to be a part of the nearby late Cenozoic volcanic provinces, and possibly represent minor partial melts which only in unusual tectonic situations arrive unmodified at the Earth's surface.  相似文献   

Greater India's place in Gondwanaland and in Asia     

J.J. Veevers  C.McA. Powell  B.D. Johnson 《Earth and Planetary Science Letters》1975,27(3):383-387

Evidence from the eastern Indian Ocean implies a Greater India in Gondwanaland. Translated without distortion to Asia, the northeast part of Greater India is found to correspond in shape with the Tibetan Plateau. With geophysical evidence, this suggests that the northeast part of Greater India underlies, presumably by underthrusting, the Tibetan Plateau.  相似文献   

Observations on the distribution of PCBs in the deepwater sediments of the Gulf of Maine     

Peter F. Larsen  Donald F. Gadbois  Anne C. Johnson 《Marine pollution bulletin》1985,16(11):439-442

Nineteen stations were occupied in the deeper regions of the Gulf of Maine to determine the geographic extent of the PCB contamination reported from recent inshore surveys. Detectable levels of PCBs were found in all 94 samples in concentrations ranging from trace amounts to 0.13 ppm (dry wt). The complex topography of the Gulf of Maine required the subdivision of the Gulf into major basin regions for proper data analysis and interpretation. Two of the three major basins, Jordan and Georges, appeared to be depositional areas for PCBs. No significant relationships existed between PCB concentration and either TOC or depth in Wilkinson Basin, however, which is located in the western Gulf of Maine closer to presumed sources.  相似文献   

Foreword     

E.S. Husebye  Editor  G.L. Johnson  Editor  Y. Kristoffersen  Editor 《Tectonophysics》1985,114(1-4)

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Studies of a wind mechanism influencing the recruitment of blue crabs in the Middle Atlantic Bight   总被引：1，自引：0，他引：1  

Donald R. Johnson  Betty S. Hester  John R. McConaugha 《Continental Shelf Research》1984,3(4):425-437

This report forms part of an on-going effort to understand the large yearly variations in blue crab harvest of Chesapeake Bay. Recent sampling programs have indicated that the larvae are transported out of the bay immediately after being spawned, and spend their first month offshore at the sea surface. Although it is well established that a mid and outer shelf southward flow occurs during all seasons in the Middle Atlantic Bight, very little is known of the nearshore currents. This study constitutes an effort to determine if the characteristically light, but northward, wind stress during the critical summer months is sufficient to drive northward counter flow at the surface and, hence, to reduce the chances that the larvae are being advected south and lost from the area of Chesapeake Bay.We investigate a local model of wind-driven currents on the continental shelf with vertical decoupling at the pycnocline. Additional driving forces include an alongshore sea surface slope and horizontal pressure gradients. With characteristic forcing values, it is found that the wind stress is indeed sufficient to drive a light northward flow within 25 to 50 km of the shoreline. We expect, then, that blue crab larval recruitment back to Chesapeake Bay may be partially dependent on summer wind stress. A comparison between a wind index time series and harvest several years later is strongly suggestive of such a dependency.  相似文献