9 Undergraduate Research Session (Posters)
Tuesday, 1 April 2003
8:30 AM - 5:30 PM
CRETACEOUS STROMATOLITIC MICROFOSSILS FROM SONORA, MEXICO
Paper number: 9-1
Program: THEME SESSIONS
Time: 8:30 AM – 5:30 PM
Authors
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Sergio R.S. Cevallos-FerrizUniversidad Nacional Autonoma de Mexico, Mexico D.F, N/A
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Elizabeth Chacon-BacaUniversidad Nacional Autonoma de Mexico, Mexico, N/A
Abstract
Ten types of microfossils preserved in chert layers that outcrop in the Huepac locality of the Tarahumara Formation in Sonora, are associated to stromatolites from the Upper Cretaceous (Turonian-Maastrichtian). They are identified based on their form, shape, size, and 3-D arrangement, as similar to extant taxa of the Cyanoprokaryota (e.g., Microcystis, Calothrix, Spirulina, Gloeocapsa, Eucapsis), Chlorophyta (e.g., Tetraedron, Chlorella), and Heterokontophyta-Bacillaryophyceae (e.g., Tabellaria, Fragilaria, Melosira). Particular ecological requirements of the extant species suggest that microfossils had either benthonic or planktonic habits. Therefore, a few of the microfossils from Huepac could participate directly in the build up of the associated Cretaceous stromatolites that apparently indicate a continental non-marine, most probably freshwater, environment. These microfossils document an important diversity of organisms living in fresh-water environments during the Upper Cretaceous in northern Mexico, and also some of the most ancient freshwater diatoms.