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"Calcareous algae and stromatolites" is shorthand for a wider array of organisms and fabrics that also includes calcified cyanobacteria, plus thrombolites and other microbial carbonates. Composition is the link: these are all important components of CaC0 sediments, from 3 Archaean to present and from the ocean floor to streams and lakes. It is hardly possible to examine limestones of any age without en countering them. Simultaneously they are fossils, sediments, and en vironmental indicators. It is the range of significance, coupled with the breadth of their distribution in time and space, which compels their study. Modern calcareous marine algae mainly include reds (corallines, squamariaceans, and the nemalialean Galaxaura) and greens (dasy cladaleans, udoteaceans, halimedaceans). Blue-greens, of course, are cyanobacteria and not algae, and significantly, although they are largely responsible for Recent tidal flat stromatolites, they are not calcified in the same way that pre-Cenozoic marine blue-greens are. It is in the freshwater environment of calcareous streams and lakes that we find modern calcified cyanobacteria, and they are commonly associated with the only major group of non-marine calcareous algae, the charophytes. However, in the past, and especially in the Palaeozoic and Mesozoic, things look radically different. Mingling with the ancestors of the modern flora are distinct, and often problematic, organisms.
Sommario
I Introduction.- 1 Calcification Processes in Algae and Cyanobacteria.- 2 Classification of Microbial Carbonates.- II Major Groups.- 3 Calcified Cyanobacteria.- 4 The Solenoporaceae: A General Point of View.- 5 Coralline Algae: Mineralization, Taxonomy, and Palaeoecology.- 6 Cyclocrinitids.- 7 Dasycladalean Algae of the Palaeozoic and Mesozoic.- 8 Cenozoic and Recent Dasycladales.- 9 Fossil Udoteaceae and Gymnocodiaceae.- 10 Recent Calcified Halimedaceae.- 11 The Genus Concept in Charophyta: Evidence from Palaeozoic to Recent.- 12 Calcification of the Charophyte Oosporangium.- 13 Calcareous Nannofossils.- 14 Fossil Calcareous Dinoflagellate Cysts.- III Algae and Stromatolites Through Time.- 15 Archaean and Proterozoic Stromatolites.- 16 Cambrian Calcareous Cyanobacteria and Algae.- 17 Ordovician Algae and Global Tectonics.- 18 Ordovician to Devonian Marine Calcareous Algae.- 19 Carboniferous Calcareous Algae.- 20 Permian Marine Calcareous Algae.- 21 Triassic and Jurassic Marine Calcareous Algae: A Critical Review.- 22 Mesozoic and Cenozoic Marine Benthic Calcareous Algae with Particular Regard to Mesozoic Dasycladaleans.- 23 Modern Stromatolites: A Review.
