The Global Theories of Amadeus W. Grabau (1870-1946): A Retrospective View

摘要

While working in China during the latter part of his career, Amadeus W. Grabau formulated his Pulsation Theory, based on his encyclopedic knowledge of Palaeozoic stratigraphic sequences in North America, Europe and Asia, that the Earth's history has been dominated by transgressions and regressions of sea level due to rhythmic pulsations of the ocean floors. He also formulated his Polar Control Theory in which he tentatively called upon the gravitational force of a stellar body that approached the Earth's south pole and caused the sialic crust to rip open and amass into a single, huge southern supercontinent, Pangaea. As he worked out the Palaeozoic history of Pangaea, Grabau traced an apparent migration of the south polar icecap from a position centered on present day Egypt in Cambrian time to Antarctica in the Jurassic. He concluded that Pangaea had drifted northward while remaining intact until the Jurassic, when it began to split into drifting continental fragments. Thus he became an advocate of both climatic polar wandering and continental drift. For the advent of life on the Earth he called upon a seeding of our planet by impacts of extraterrestrial bodies containing living organisms. Now that the theory of plate tectonics validates horizontal motions of crustal plates, and meteorites from Mars have been found to carry possible evidence of past life, we will reexamine Grabau's global theories in the light of our present knowledge. We will find that although many aspects of Grabau's global theories are unacceptable, some of them are closer in spirit to those we favor today than were the theories held by most of his contemporaries.