Tests of Plate Tectonics1
Geological and geophysical data from the ocean basins and the continents are now sufficiently abundant to demonstrate that all proposed models for the new global tectonics contain serious errors. For example, several sets of paleoclimatic data—specifically, the distribution on the continents and shelves of ancient evaporites, carbonate rocks, coals, and tillites—appear to be explicable only if the present positions of the rotational axis, continents, and ocean basins have been constant for at least 1,600 m.y. The distributions of fossil invertebrate and tetrapod faunas and floras likewise indicate the constancy of position of the rotational axis, continents, and ocean basins for at least 570 m.y. Faunal-realm studies are proving to be extremely useful, because many of them demonstrate that the continents have been in about their present relative positions since Proterozoic time.
A possibly fatal flaw in the plate-tectonics hypothesis is that the topologic requirements for moving the Americas away from Eurafrica eliminate any possibility of such movement unless the earth has expanded greatly during the last 150–200 m.y. Studies of climatic and biozoologic zones of the Mesozoic and Cenozoic show that expansion has not taken place. Other space requirements for the continents do not permit east-west movements since Archean time in the Northern Hemisphere, a conclusion now confirmed by the presence of continental crust across the North Atlantic beneath the Faeroe-lceland-Greenland ridge. North-south movements of individual continents are limited to a few hundred kilometers—on the basis of paleoclimatic and paleontologie data. Movements involving the “opening” and “closing” of the Tethys—from present-day Spain to New Guinea—are restricted to distances of less than 300 km by detailed field geological and geophysical studies. If seafloor spreading is taking place in the Tethyan belt, lateral movements have been—and are—restricted to mantle movements and the overlying lithosphere is detached from the mantle.
Ocean-basin studies show that island-arc trench fills, where subduction supposedly takes place, are undeformed. The volumes of undeformed sedimentary rocks in Layer 1 indicate that either (1) seafloor spreading has not taken place since late Mesozoic or earlier time, (2) subduction must take place seaward from the island arc trenches, or (3) there is no such process as subduction. Detailed studies of the Lesser Antilles and Tonga-New Zealand arcs prove that aseismic island chains seaward from both arcs have been in their same relative positions since mid-Mesozoic and late Paleozoic times, respectively. Preliminary studies of several other island-arc systems lead to similar conclusions.
Sediment fills in fracture zones crossing midocean ridges also are undeformed—a remarkable fact if seafloor spreading is taking place. Many of these fractures continue onshore into the continents, where the proved senses of movement are the opposite of those predicted by "transform-fault" solutions. “Transform-fault” solutions, moreover, are accounted for more logically by known gravity models of midocean ridges than by hypothetical “plate” motions.
JOIDES drilling results have been hailed as a “remarkable confirmation” of plate-tectonics predictions. Numerous alleged basalt basements have baked upper contacts, so that it is doubtful that such basalts really are basement. The first dating of such basalts from JOIDES coreholes beneath Mesozoic rocks showed the basalt to be late Tertiary or younger. Thus another prop of the new global tectonics begins to crumble, and the age of the ocean basins remains unknown.
A possible clue to the age of the ocean basins is the increasing number of discoveries of ancient rocks from the ocean basins and midocean ridges. Rocks ranging in age from 797 m.y. to 1,590 m.y. have been found from the Atlantic, the Pacific, and possibly the Indian Oceans. None of the ancient samples fit modern notions of plate tectonics.
Figures & Tables
The general theme of this publication is the assessment and reassessment of various data, observations, and ideas about the earth as they relate to the concept that has come to be known as plate tectonics. Much widely scattered material was brought together for this publication, and its 24 papers contain an abundance of worldwide references that are important in studying plate tectonics.