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Paleo Lab 3 - Micropaleontology

Paleo Lab 3 - Micropaleontology - PALEO LABORATORY 3 PAGE 1...

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PALEO LABORATORY # 3, PAGE 1 PALEO LAB # III - MESOZOIC AND CENOZOIC MICROPALEONTOLOGY A. Kingdom Protoctista/Protista During this lab, we will study various types of marine algae and the groups of autotrophic protists, foraminiferans and radiolarians that were important during Mesozoic and Cenozoic times. As we have seen in Laboratory # II, a number of photosynthetic divisions of Protoctista have substantial fossil records. These include the divisions Phaeophyta (brown algae), Rhodophyta (red algae), Bacillariophyta (diatoms), Haptophyta (calcareous nannoplankton or coccoliths; diatoms and calcareous nannoplankton are often placed within the Chrysophyta), Pyrrhophyta/Dinoflagellata (dinoflagellates) and Chlorophyta (grass-green algae). 1. Division Pyrrhophyta/Dinoflagellata You have probably read of the phenomenon termed "red tide", where ocean water turns a reddish color and marine animals die by the millions. Red tide is due to the rapid multiplication and super-abundance of dinoflagellates, which produce a toxin called "paralytic shellfish poison". However, other dinoflagellates are not as destructive to the marine environment. Some types are largely responsible for luminescence in the seas, where the surface waters of the ocean seem to "twinkle" at night from the light produced by these organisms. Dinoflagellates are very numerous organisms; they may be found in concentrations of up to six million individuals per liter of sea water. Most dinoflagellates are marine planktonic. However, some species live in fresh water, others may be marine benthonic and other types are symbiotic or parasitic. During certain times in their life history, the "shells" of dinoflagellates are differentiated into two layers. The outer layer, or theca, is composed of a cellulose-like substance which decays when the algae dies. However, the inner layer (test or cyst) is made of a tough, resistant organic substance which is easily fossilized. Because of the abundance, preservability and minute size of dinoflagellates they are very important index fossils for determining the age and paleoecology of ancient sedimentary environments. Dinoflagellate tests with long spines (termed processes) are often referred to as Hystricospheres (Jurassic-Recent). Hystricospheres are planktonic and are usually found in open marine environments. Other dinoflagellates in which the spines are short or absent (proximate tests) are most often found in near-shore environments. However, the distribution of the hystricosphere and proximate types is gradational and determination of the paleoecology of fossil dinoflagellates is somewhat complex. A third type of cyst, termed cavate, forms a distinct central body (endocyst) beneath the tabulation. It is difficult to relate fossil cysts to the "motile" phases of living dinoflagellates. However, the morphology of the cyst may reflect the plate positions of the motile phase. This paratabulation (pseudotabulation) is often used for classification of fossil cysts. The plate equivalents are termed apical, intercalary, precingular, cingular, postcingular and antapical.
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