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Title: Growth rings in secondary xylem : their formation and interpretation through geological time
Author: Creber, Geoffrey Tremain
Awarding Body: University of London
Current Institution: Royal Holloway, University of London
Date of Award: 1984
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The secondary wood formed by cambial activity in the growth of trees records with varying degrees of precision the amount of seasonality and other aspects of the climate under which it grew. A survey is presented of the extent to which this climatic 'data-store' can be directly 'read back', based on the extensive literature on the environmental control of wood formation in modern plants. This led to the investigation of growth ring characters in selected fossil and recent wood in the course of which a cyclic phenomenon, apparently under endogenous control, was demonstrated. The potential of this information to deduce aspects of the palaeoclimate from fossil wood (of age extending back some 370 million years) is then considered. Attention was directed particularly to three intervals of geological time, namely the Upper Devonian, the Permo-Carboniferous and the later Mesozoic in which growth ring characteristics present features of particular interest. A classification of growth ring features is developed and five categories are defined. Some of these data are derived from direct observation of fossil wood material by the author and some from the literature. Growth ring characteristics are plotted on palaeo-reconstruction maps and the climatic significance is considered in relation to other indicators of palaeo-climate. Consideration is given to the phenomenon of tree growth (and very substantial increments) in high latitudes during two phases of geological time---the Permian and the later Mesozoic. At these times major forest growth evidently extended far beyond the present latitudinal range. Consideration of the radiation energy input at high latitudes, and the effect of a generally more isothermal global climate suggests that these growth ring phenomena can be explained in uniformitarian terms without the need to invoke shift in axial inclination or similar processes as some, have advocated.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Paleontology