Cenomanian-Turonian (Upper Cretaceous) foraminifera from the westernmost Colorado Plateau, southwest Utah, U.S.A

Foraminifera from the Cenomanian-Turonian Dakota Formation, Straight Cliffs Formation, Iron Springs Formation, and Tropic Shale of southwest Utah are described and illustrated in detail. The assemblage comprises 37 taxa including 27 agglutinated species and only nine calcareous taxa. The association...

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Bibliographic Details
Published in:Micropaleontology 2013-01, Vol.59 (6), p.555-578
Main Authors: Tibert, Neil E., Leckie, R. Mark
Format: Article
Language:English
Subjects:
Bentonite
Biostratigraphy
Canyons
Geographic distribution
Geology
Mesas
Shales
Straits
Stratigraphy
Taxa
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Summary:Foraminifera from the Cenomanian-Turonian Dakota Formation, Straight Cliffs Formation, Iron Springs Formation, and Tropic Shale of southwest Utah are described and illustrated in detail. The assemblage comprises 37 taxa including 27 agglutinated species and only nine calcareous taxa. The associations of the foraminifera can be summarized on the basis of their distributions relative to geologic age and formation. The lowermost units of the Dakota Formation in southwest Utah and Coal Mine Mesa Arizona are characterized by a Trochammina rutherfordi mellariolium-Verneuilinoides perplexus association. The uppermost strata of the Dakota Formation and lower Tropic Shale (upper Cenomanian) are characterized by a Trochamminoides apricarius-Haplophragmium arenatum association. Strata assigned to the lower-to middle Turonian Iron Springs and Straight Cliffs Formation are highly variable with respect to foraminiferal distributions. Lower Turonian deposits from the Tropic Shale, however, contain an association of Reophax inordinata and Ammomargulina lorangerae. The temporal and spatial variability of the foraminifera are attributed to transgressive-regressive facies shifts during deposition of the Greenhorn Marine Cycle. We recognize four paleoecological associations of agglutinated foraminifiera that include: (1) a marsh assemblage dominated by Trochammina and Miliammina; (2) a central estuary assemblage dominated by Ammobaculites and Trochammina; (3) a distal estuary assemblage dominated by Verneuilinoides, Textularia, and Trochamminoides; and (4) a shelf assemblage dominated by Haplophragmium and Reophax.
ISSN:0026-2803
1937-2795
DOI:10.47894/mpal.59.6.03