A Decade of Challenge the Future of Biogeography

1985 ◽  
Vol 4 (2) ◽  
pp. 187-196 ◽  
Author(s):  
Gareth Nelson
Keyword(s):  
Critical Evaluation ◽  
Pacific Basin ◽  
Main Task ◽  
Radial Expansion ◽  
Sea Floor ◽  
Biogeographic Patterns ◽  
The Pacific ◽  
The Difference ◽  
Sea Floor Spreading ◽  
East West

According to Croizat's global synthesis, the main biogeographic patterns include trans-Atlantic, trans-Pacific, trans-Indoceanic, Boreal, and Austral. Geological and geophysical theories vary, but agree that sea-floor spreading in the Pacific is different in its effect from that in other ocean basins. The difference allows for radial expansion of the basin and not merely east-west displacement of continental areas. Biogeographic data suggest that bipolar (boreal + austral) distributions are to be reckoned among the results of sea-floor spreading in the Pacific. Data from one group of inshore fishes (family Engraulidae) exemplify this notion and add, as terminal parts of the differentiation of the Pacific Basin, trans-Panama marine vicariance and a collateral occurrence in freshwater of tropical South America. These findings corroborate Croizat's synthesis. They suggest that the critical evaluation of that synthesis will be the main task of biogeography over the next decade. They indicate that within the area of systematics, evaluation will require a cladistic approach and the elimination of paraphyletic groups from classification.

A Measurement of Seismic Anistropy in the Northeast Pacific

1971 ◽  
Vol 8 (9) ◽  
pp. 1056-1064 ◽  
Author(s):  
C. E. Keen ◽  
D. L. Barrett
Keyword(s):  
Seismic Refraction ◽  
Maximum Velocity ◽  
Mean Value ◽  
Ocean Basin ◽  
P Wave ◽  
Sea Floor ◽  
P Wave Velocity ◽  
The Pacific ◽  
Magnetic Lineations ◽  
Sea Floor Spreading

A seismic refraction experiment was conducted in the Pacific Ocean basin, off the coast of British Columbia, Canada. The purpose of these measurements was to obtain an estimate of the anisotropy of the mantle P-wave velocity in the area and to relate this parameter to the direction of sea floor spreading. The results show that the crustal structure is similar to that measured elsewhere in the Pacific basin. Significant anisotropy of the mantle rocks is observed; the direction in which the maximum velocity occurs being 107° and the change of velocity, about 8% of the mean value, 8.07 km/s. The direction of maximum velocity does not coincide exactly with the direction of sea floor spreading, 090°, inferred from magnetic lineations.

A Method for Quantitative Evaluation of Carbonate Dissolution in Deep-Sea Sediments and its Application to Paleoceanographic Reconstruction

1978 ◽  
Vol 10 (1) ◽  
pp. 112-129 ◽  
Author(s):  
Teh-Lung Ku ◽  
Tadamichi Oba
Keyword(s):  
Quantitative Evaluation ◽  
Deposition Rate ◽  
Deep Sea ◽  
Bottom Water ◽  
Carbonate Dissolution ◽  
Present Value ◽  
Dissolution Rates ◽  
Sea Floor ◽  
The Pacific ◽  
The Difference

A method is proposed by which the degree of attrition of the tests of certain foraminifera species, such as Globorotalia menardii and Globorotalia tumida, is used to “scale” the amount of CaCO3 that has been dissolved from sediment. The scale is calibrated experimentally in the laboratory. The method has been applied to three calcareous cores from the Pacific and the Indian Oceans. It is shown that the original CaCO3 contents in these cores were high (82–95%) and relatively uniform compared to the present down-core values. About 65 to 85% of the originally deposited CaCO3 has been dissolved, corresponding to dissolution rates on the order of 0.1-0.3 moles/cm2/yr. These results indicate that appreciable solution could have occurred on sea floor rich in calcareous sediments and that the variation in CaCO3 content in a core may have resulted largely from dissolution. The difference in the degree of solution between glacial and interglacial sediments in these cores is not so distinct, with ⋍ 10% less intense dissolution during glacial times on the average. However, the dissolution minimum occurring around the late Wisconsin glaciation (10,000–20,000 yr B.P.) previously noted in several cores elsewhere is confirmed. At that time, near the site of core M70 PC-20 in the southwest Pacific, the CO32− concentration of the bottom water is estimated to have been approximately 5% higher than the present value, and the calcite lysocline was about 300 m deeper. To evaluate possible variations in CaCO3 deposition rate across the glacial-interglacial transitions requires precise age control, which the present study lacks.

A. Wegener - O. Ampferer - R. Schwinner: The First Chapter of the "New Globale Tectonic"

1984 ◽  
Vol 3 (2) ◽  
pp. 178-186 ◽  
Author(s):  
Helmut Fiügel
Keyword(s):  
Pacific Plate ◽  
Benioff Zone ◽  
Sea Floor ◽  
Middle Atlantic ◽  
The Pacific ◽  
Sea Floor Spreading

Between 1906-1948, Wegener, Ampferer, and Schwinner worked out many tectonic concepts which are today parts of the New Globale Tectonic, including the idea of convection currents, the origin ofthe Middle Atlantic Ridge in connection with sea-floor spreading, the concept of the "Benioff-Zone", the subduction of parts of the Pacific plate under the continents, and the linkage of these features with volcanism. Many of these ideas were soon forgotten and had to be "rediscovered" once again.

Icelandia

2021 ◽  
Author(s):  
Gillian Foulger ◽  
Laurent Gernigon ◽  
Laurent Geoffroy
Keyword(s):  
Continental Crust ◽  
Structural Complexity ◽  
Ne Atlantic ◽  
Sea Floor ◽  
Passive Margins ◽  
The North ◽  
The Pacific ◽  
Ne Atlantic Ocean ◽  
Sea Floor Spreading ◽  
North And South

<p>The NE Atlantic formed by complex, piecemeal breakup of Pangea in an environment of structural complexity. North of the present-day latitude of Iceland the ocean opened by southward propagation of the Aegir ridge. South of the present-day latitude of Iceland breakup occurred along the proto-Reykjanes ridge which formed laterally offset by ~ 100 km from the Aegir ridge to the north. Neither of these new breakup axes were able to propagate across the east-westerly striking Caledonian frontal thrust region which formed a strong barrier ~ 400 km wide. As a result, while sea-floor spreading widened the NE Atlantic, the Caledonian front region could only keep pace by diffuse stretching of the continental crust, which formed the aseismic Greenland-Iceland-Faroe ridge. The magmatic rate there was similar to that of the ridges to the north and south and so the stretched continental crust is now blanketed by thick mafic flows and intrusions. The NE Atlantic also contains a magma-inflated microcontinent – the Jan Mayen Microplate Complex, and an unknown but probably large amount of stretched continental crust blanketed by seaward-dipping reflectors in the passive margins of Norway and Greenland. The NE Atlantic thus contains voluminous continental crust in diverse forms and settings. If even a small portion of the sunken continental material contiguous with the Greenland-Iceland-Faroe ridge is included the area exceeds a million square kilometers, an arbitrary threshold suggested to designate a sunken continent. We have called this region Icelandia. The conditions and processes that funneled large quantities of continental crust into the NE Atlantic ocean are common elsewhere. This includes much of the North and South Atlantic oceans including both the seaboards and the deep oceans. Nor are such processes and outcomes confined to oceans bordered by passive margins. They are also found around the Pacific rims where subduction is in progress. Indeed, these conditions and processes likely are generic to essentially all the world's oceans and are potentially also informed by observations from intracontinental extensional regions and land-locked seas.</p>

THE CONTINENTAL ACCRETION AND FOLDING OF AUSTRALIA BY PACIFIC SEA FLOOR UNDERSPREADING

1972 ◽  
Vol 12 (2) ◽  
pp. 70
Author(s):  
A.C.M. Laing
Keyword(s):  
Solar System ◽  
Liquid Core ◽  
Continental Drift ◽  
Horizontal Stress ◽  
The Other ◽  
Pacific Basin ◽  
Sea Floor ◽  
The Earth ◽  
The Pacific ◽  
Continental Accretion

The theory of continental drift is criticised for being based on a number of fallacies.The fallacies discussed include polar wandering and Permian glaciation in Australia. Both are regarded as nonexistent. Data are presented to indicate firstly that Australia has grown by continental accretion and secondly that this growth has taken place under a horizontal stress directed outwards from the Pacific Basin. It is postulated that this horizontal stress is caused by a gradually intensifying bump in the liquid core of the earth, which is believed to have formed in the condensation and accretion stage of the solar system, mainly from two lumps of different composition and properties, one now constituting the Pacific Basin, the other the remainder of the Earth.A corollary to this hypothesis is that the structural equivalents of the petroliferous basins of North America lie under the Tasman, Coral, and Timor seas.

Probably the Best Theory on Earth

2018 ◽  
Author(s):  
Roy Livermore
Keyword(s):  
Geomagnetic Field ◽  
Convincing Evidence ◽  
Ocean Floor ◽  
Bar Code ◽  
Sea Floor ◽  
Ocean Ridges ◽  
Sea Bed ◽  
The Pacific ◽  
Sea Floor Spreading

The magnetic bar-code on the ocean floor provides convincing evidence of moving continents, yet, as with the discovery of the structure of DNA, few are convinced—at first. Drilling in the deep oceans and geochemical work at mid-ocean ridges provides further evidence in support of the Vine–Matthews Hypothesis. Application of the hypothesis to data collected in the Pacific and Atlantic Oceans establishes sea-floor spreading as the process that creates new oceans and, in conjunction with reversals of the geomagnetic field, stamps the bar-code into the rocks beneath the sea bed.

Magnetic anomalies in the Pacific and sea floor spreading

1968 ◽  
Vol 73 (6) ◽  
pp. 2069-2085 ◽  
Author(s):  
W. C. Pitman ◽  
E. M. Herron ◽  
J. R. Heirtzler
Keyword(s):  
Magnetic Anomalies ◽  
Sea Floor ◽  
The Pacific ◽  
Sea Floor Spreading
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