Community paleoecology and biogeography of the Jurassic (Bajocian-Oxfordian) Sundance Seaway in the Bighorn Basin of Wyoming and Montana, U.S.A.
Kusnerik, Kristopher Michael
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The composition of marine communities is controlled by colonization of newly available habitat, development of community associations, and community variation in response to a gradient of environmental conditions. The Jurassic Sundance Seaway of the Bighorn Basin, Wyoming and Montana provides an ideal case study for determining the role of these factors on community composition and variation. The global provenance of taxa found in the Seaway support reconstructions depicting a single, northern entranceway. This, along with the Seaway’s length and shallow depth, likely caused restrictions on taxa able to enter the Seaway under normal conditions, leading to communities with low diversity and low evenness. Ordination analysis suggests the primary factor controlling community composition was a complex gradient related to water depth. Secondary factors include substrate, salinity, and a carbonate to siliciclastic transition. These patterns are typical of Jurassic marine communities globally.