Sequence stratigraphy and depositional facies of Lower Ordovician cyclic carbonates, southern Missouri

“The Lower Ordovician cyclic carbonate strata of southern Missouri were deposited in a warm, shallow, epeiric sea environment on a fully aggraded carbonate platform. Sedimentological characteristics distinguish the Jefferson City and Cotter Dolomites from the underlying Gasconade and Roubidoux Formations. The Jefferson City and Cotter Dolomites exhibit an increased occurrence of chalcedonic chert nodules in a very similar shape and texture to the gypsum and anhydrite nodules common on modern sabkha supratidal flats. Casts of halite and gypsum lath ghosts also exist in these strata. Contrastingly, such chert nodules are rarely found in the underlying Roubidoux and Gasconade Formations. Facies analysis from drill-cores and outcrop sections provides the basis for identifying two major meter-scale cycle types: type I (dominated by subtidal facies) and type II cycles (dominated by peritidal facies). The cycle stacking patterns, facies changes, and the overall resemblance of Fischer plots made from the widely spaced sections argue for an eustatic control on sea-level fluctuation on the platform. Interbasinal correlation with other North American basins was established via biostratigraphy and comparison of the Fischer plots. The 3rd-order sequence boundaries from the Ozarks appear correlative with those described for other regions with the exception of sequence 3 from the Ozarks. However, Fischer plots from the separate basins could not be correlated with any certainty, since visual comparison of the plots did not reliably suggest the proper correlation as indicated by biostratigraphy. Regional tectonic and autocyclic controls on meter-scale cycle formation probably mask the eustatic signal on the continent”--Abstract, page iii