By John L. Wray (Eds.)
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Extra resources for Calcareous Algae
Geologic range The Solenoporaceae are predominantly Paleozoic and Mesozoic algae, yet a few taxa range well into the Cenozoic (Fig. 34). Two genera, SoZenopora and Parachaetetes. have exceedingly long geologic ranges, but with some gaps in their record. Parachaetetes has only recently been reported from the Late Carboniferous (Pennsylvanian), where previously solenoporaceans were unknown (Heckel, 1975). Members of this family seem to be most common and widespread 49 Fig. 32. Parachaetetes. Vertical section.
4. Intracellular Cell wall Extracellular Surficial Fig. 10. Diagrammatic sketch of calcium carbonate deposition sites in algae. (After Arnott and Pautard, 1970). In general, internal calcification is related to cellular morphology, metabolism, and the selective absorption or assimilation of specific carbonate salts. Little-understood, complex reactions of these factors result in carbonate precipitation and distribution within the thallus. The calcium carbonate is a consequence of the interaction of carbonate, or biocarbonate, with calcium under alkaline conditions, but the process by which carbon dioxide is released or absorbed to achieve this result is not clear.
Diagenetically formed calcareous filaments of endol ithic algae in rock cavity. Recent, Bermuda. Scanning electron micrograph. (From Schroeder, 1972). There has been little attempt to classify fossil calcareous blue-green algae. Pia (1926) considered various filamentous forms, including Girvanella and Sphaerocodium, along with Collenia and Cryptozoon, in a discussion of blue-green algae and stromatolites. However, in 1927 Pia introduced the artificial group "Porostromata" to separate forms with a definite microstructure consisting of filaments (of unknown systematic position, butprobably belonging to the green or blue-green algae) from the "Spongiostromata" (forms lacking microstructure), in which he placed algal stromato1ites.
Calcareous Algae by John L. Wray (Eds.)