|
Plantae |
Department of Botany, Cornell University, Ithaca, N.Y., U.S.A.
Department of Palaeontology, British Museum (Natural History), Cromwell Road, London S W 7
Department of Geology, Sedgwick Museum, Downing Street, Cambridge
Department of Geology, University Science Laboratories, South Road, Durham
Department of Geology, University Science Laboratories, South Road, Durham
Department of Geology, The University, Mappin Street, Sheffield 1
This chapter includes all benthonic algae (planktonic algae are in Chapter 2), the family Prototaxitaceae, bacteria and fungi. In some of these groups the fossil record is very inadequate, and the method of documentation has been varied accordingly.
THE CALCAREOUS ALGAE
Algae are the only fossil group which have a widespread development in the Precamb. The earliest fossil records, dating from at least 2700 m.y., are stromatolites possibly belonging to the Chlorophyceae and Cyanophyceae. Definite cellular microorganisms, including Gunflintia, Animikiea and Archaeorestis identified as blue-green algae, have been found in the Gunflint Chert, M. Precamb, Canada, and are 1900 m.y. old (Barghoorn and Tyler 1965; Cloud 1965). Even at the earliest period there seems to have been considerable diversity in the group and since then continuous evolutionary progress has taken place. Divergence, convergence and parallelism of form and habit in the different classes of algae during their geological history is striking (Fritsch 1948). Thus the structural pattern of the Chlorophyceae, Cyanophyceae and in most part the Rhodophyceae is remarkably parallel from unicellular motile and colonial, through filamentous to complex thalloid forms.
The great majority of living algae do not produce skeletons but of the known fossil algae almost every genus is calcareous and many are important rock builders. Maslov (1961) has shown that carbonates can be deposited by algae in six different ways. Of these the "mixed" or "stromatolitic" process and the "biochemical" process are most important in the Precamb. The "organic" and "physiological" processes emerged in the Camb but
...
This 250-word extract was created in the absence of an abstract.
This article has been cited by other articles:
 |
|
 |
|
  I. I. BUCUR, W. KIESSLING, and R. A. SCASSO RE-DESCRIPTION AND NEOTYPIFICATION OF ARCHAMPHIROA JURASSICA STEINMANN 1930, A CALCAREOUS RED ALGA FROM THE JURASSIC OF ARGENTINA Journal of Paleontology, 2009; 83: 962 - 968. [Full Text] [PDF]
|
|
