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- Grenholm, Mikael, et al.
(författare)
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A hypothesis for Proterozoic-Phanerozoic supercontinent cyclicity, with implications for mantle convection, plate tectonics and Earth system evolution
- 2015
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Ingår i: Tectonophysics. - : Elsevier BV. - 0040-1951. ; 662:S1, s. 434-453
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Tidskriftsartikel (refereegranskat)abstract
- We present a conceptual model for supercontinent cycles in the Proterozoic-Phanerozoic Eons. It is based on the repetitive behavior of C and Sr isotopes in marine carbonates and U–Pb ages and εHf of detrital zircons seen during the Neoproterozoic-Paleozoic and Paleoproterozoic Eras, respectively. These records are considered to reflect secular changes in global tectonics, and it is hypothesized that the repetitive pattern is caused by the same type of changes in global tectonics. The fundamental premise of this paper is that such repetitive changes should also be recorded in orogenic belts worldwide. This carries the implication that Neoproterozoic-Paleozoic orogenic belts should have Paleoproterozoic equivalents. It is proposed that this is the case for the East African, Uralides and Ouachita–Alleghanian orogens, which have Paleoproterozoic analogs in the West African–Amazon, Laurentian and East European cratons, respectively. The Neoproterozoic-Paleozoic orogenic belts are not isolated features but occur in a specific global context, which correspond to the relatively well-constrained Neoproterozoic break-up of Rodinia, and the subsequent Late Paleozoic assembly of Pangea. The existence of Paleoproterozoic equivalents to Neoproterozoic-Paleozoic orogens requires that the same cycle defined the Paleoproterozoic. We therefore hypothesize that there were Paleoproterozoic supercontinents equivalent to Rodinia and Pangea, and that Proterozoic-Phanerozoic supercontinents are comprised of two basic types of configurations, equivalent to Rodinia (R-type) and Pangea (P-type). The Paleoproterozoic equivalent of Rodinia is likely the first supercontinent to have formed, and Proterozoic-Phanerozoic supercontinent cycles are therefore defined by R- to R-type cycles, each lasting approximately 1.5 Gyr. We use this cyclic pattern as a framework to develop a conceptual model that predicts the configuration and cycles of Proterozoic-Phanerozoic supercontinents, and their relation to mantle convection and Earth system evolution.
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| 2. |
- Nilsson, Staffan, 1972-
(författare)
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Den potentiella människan : En undersökning av teorier om självförverkligande
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- “What characterizes an acceptable theory of self-realization?” The thrust of the present dissertation is towards seeking an answer to this central problem, which stems from the fundamental human experience that life involves change, and that in a modern society such change is often expected to be towards a realization of potentials and the good life for the individual. The dissertation has a three-fold purpose. The first is to clarify the content of five modern theories of self-realization from three academic fields. The theories are those of the psychologist Abraham H. Maslow, the philosophers Charles Taylor and Alan Gewirth, and the theologians Reinhold Niebuhr and Bernard Lonergan. These are methodologically studied by the help of seven analytical questions. The second purpose is to perform a lengthwise comparatative analysis of the five theories, the results of which lead to the third; namely to critically discuss several elements of the reality of human life which have proven to be missing or supressed in much of the material.The theoretical framework for the dissertation runs along two axes: one concerns what is developed as a distinction between internalism and relationalism, and the other is to cast a critical light on the lack of attention paid by the the theories of self-realization to experiences which run counter to optimistic ideas of individual development, such as death, loss and dependence. The dissertation concludes with an outline for a constructive position based on the necessity of a theory’s closeness to experience, and on the need for reconcilitation of what may seem to be unabridgeble in human life. A theory of self-realization must do more than formulate positive conditions for change. It must also take into consideration conditions that are not directly related to, and sometimes even run contrary to, realization of the self.
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