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The Souris River formation is a Devonian subsurface formation, presently tilted southwestward, which is encountered in southern and central Saskatchewan in wells drilled for oil, potash, and helium at depths ranging from a maximum of 6,142 feet below sea-level near the international boundary to a minimum of 821 feet below sea-level near the Souris River subcrop edge in central Saskatchewan.
Stromatoporoids were recovered from cores 2-4 inches in diameter in fragmental dolomitic limestone of the lower Souris River formation. The wells are widely spaced over a belt more than 250 miles long in southern Saskatchewan.
The stromatoporoid faunas are represented by Atelodictyon and Stictostroma of the family Clathrodictyidae; Actinostroma and Trupetostroma of the Actinostromatidae; Amphipora, Idiostroma, and Stachyodes of the Idiostromatidae; and Ferestromatopora, Stromatopora, Parallelopora, and Synthetostroma of the Stromatoporidae. The faunas most closely resemble those described from the lower Upper Devonian Moberly member of the Waterways formation of northeastern Alberta. Members of the family Idiostromatidae are the most common in numbers of specimens if not bulk. The Stromatoporidae is the second most important family. Trupetostroma stands out among the Actinostromatidae.
Most of the stromatoporoid coenostea are whole, especially the massive forms. Thin bands of matrix material around most specimens are dark brown organic lutitic limestone. The hemispherical coenostea appear to have been rolled around and show no preferred orientation. These coenostea may have been transported a short distance and deposited outside of their normal habitat. The elongate coenostea of members of the Idiostromatidae are oriented parallel with bedding surfaces and show a slight but inconclusive suggestion of polarity. The lithologic character of the described matrix material is common in association with Amphipora and Stachyodes wherever they are found. These genera are likely not oriented in their position of growth. The absence of any suggestion of a base of attachment in Amphipora is puzzling.
The internal preservation of the stromatoporoid coenostea is good considering the nature of the over-all lithologic character of the stratigraphic unit. Gallery spaces are mostly infiltrated by calcium carbonate.
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