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Title: Construction and ecology of icehouse algal reefs
Author: Forsythe, G. T. W.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2000
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Tropical reefs, constructed during the late Palaeozoic icehouse climate, suffered high amplitude, high frequency sea level changes (Gondwanan glaciation). Rare three-dimensional outcrops of Virgilian (Pennsylvanian) and Wolfcampian (Early Permian) reefs occur in the Hueco Mountains, Texas. The reefs form part of a highly cyclical carbonate platform succession that suffered repeated emergence. The reefs are dominated by platy 'phylloid algae', these algae may belong to either Rhodophyta or Chlorophyta. The erect, recumbent or cyathiform genus Eugonophyllum is interpreted as belonging to the green algal family Halimedaceae. Eugonophyllum is the dominant reef building alga in the area studied. The prostrate phylloid alga Archaeolithophyllum is interpreted as belonging to the red algal family Corallinaceae. Archaeolithophyllum does not occur in the reefs, but forms extensive biostromes. The dominant constructional mechanism for reef formation has previously been regarded as sediment baffling and trapping, mainly by erect phylloid algae. Analysis of reef ecology clearly shows that these algae were in fact capable of forming a framework, to which considerable stability was added by secondary encrusting organisms such as the problematica Tubiphytes (or Shamovella) and Archaeolithoporella. Complex, multiple encrustations (both in-vivo and post-mortem) of these organisms were a fundamental element of reef construction. The effect of diagenesis on the phylloid algae and Tubiphytes are illustrated. Tubiphytes were found to be commonly altered on the ultrastructural scale, inferred to be by dissolution and reprecipitation, but with some preservation of microstructural features such as laminae.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available