. Bulletins of American paleontology. Thornton Creek Member: Day and Whalen 129 Biostratigraphy Brachiopods Eleuthrokomma wendtei Schizophoria stelcki Pseudoatrypa sp. Desquamatia (Independatrypa) sp. Cyrtina triquetra Cranaena sp. Strophodonta (S.) sp. Moderate Diversity Fauna Conodont Ichodus subterminus Upper subterminus Fauna? = Upper disparilis Zone (Johnson and Klapper, 1990) vf^ <^^ .0^° ^-^-^ 10 Trace Fossil Thallasinoides {Cruziana Ichnofacies) Open Marine Conditions /I Brachiopod Athyris vitatta. Low Diversity (monospecific) Fauna Restricted Marine Conditions 5 - 0 -I
. Bulletins of American paleontology. Thornton Creek Member: Day and Whalen 129 Biostratigraphy Brachiopods Eleuthrokomma wendtei Schizophoria stelcki Pseudoatrypa sp. Desquamatia (Independatrypa) sp. Cyrtina triquetra Cranaena sp. Strophodonta (S.) sp. Moderate Diversity Fauna Conodont Ichodus subterminus Upper subterminus Fauna? = Upper disparilis Zone (Johnson and Klapper, 1990) vf^ <^^ .0^° ^-^-^ 10 Trace Fossil Thallasinoides {Cruziana Ichnofacies) Open Marine Conditions /I Brachiopod Athyris vitatta. Low Diversity (monospecific) Fauna Restricted Marine Conditions 5 - 0 -I CStSdG B Mill Sequences 3rd Order. Cambrian IVI W P G F/R Text-figure 6.—Faunal data from stratigraphic section A illustrating the stratigraphic positions of the low-diversity restricted-marine Athyris Fauna {Table 1. samples IF and 2F) and moderate diversity, open marine ElcinlwrokoDiDiii-Schi-nphoria brachiopod Fauna (Table 1. sample 3F), conodont. and trace fossils. Abbreviations as in Text-figure 5. shallow marine conditions to subtidal open marine conditions below fair-weather wave base, to shallow open-marine conditions within fair-weather wave base. The sedimentologic and faunal data imply that the three parasequences represent one genetic sequence (Text-figs. 5 and 6). Parasequence 1 and the lower por- tion of parasequence 2 are interpreted as a Transgres- sive System Tract (TST) recording initially restricted and then open marine conditions (Text-fig. 5). The low-diversity faunas recovered from those intervals support this interpretation. Max- imum flooding occurs within the upper part of paras- equence 2 as indicated by the diverse and open-marine brachiopod fauna dominated by Eleiirlierokonima. Athyris, and Schizophoria (Text-hgs. 5 and 6). The up- permost part of parasequences 2 and all of parasequ- ence 3 (Text-hg. 5) are interpreted as High-Stand Sys- tem Tract (HST). The thinning-upward nature of the parasequences and the increase in thickn
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