In this study, paleoecologic interpretations have been baaed on regional and local stratigraphy,bed geometry, lithic succession, petrology/petrography, and macro- and microfauna. Stratigraphic and palepecplogic conclusions are strongly interactive. Initial paleoecologic conclusions are strongly interactive. Initial paleoecologic interpretations must employ, among other things the best available stratigraphic information. Once the general paleoecologic framework: becomes established, stratigraphic interpretations can be tested against the environmental picture. For example, if at one locality the eptire thickness of a marine interval is considered to have been deposited under extreme nearshore conditions, it Is not logical to expect the same marine interval to have been, formed under totally nearshore conditions over an extensive geographic area. Conversely, a series of scattered isolated, Iithologically similar outcrops each with a totally nearshore fauna predicts, that the rodcs are not, products of the same marine episode
Paleoecologic studies probably overemphasize two factors of ancient environments, water depth and substrate. Depth, is the single most important controlling factor for modern marine Invertebrates as a group, but this importance is lessened considerably if the bathymetric range Involved is compressed from several hundreds of meters to ten meters or so. Many "depth" conclusions in recent paleoecologic literature prove to be energy classifications, relative to wave base (sensu. Rich, 1951a). Substrate, is also probably overemphasized because it Is the one tangible and virtually reproducible aspect of every ancient environment, and the only one that can be observed directly at the present time.
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“Pennsylvanian rocks exposed in Knox, Peoria, Fulton, and Schuyler Counties in northwestern Illinois include 11 major marine units. The oldest marine unit is late Atokan and the youngest is early Missourian; the remainders are Desmoinesian in age. Each unit has produced at least some conodonts, and the more than 200 samples produced an aggregate total in excess of 160,000 conodont specimens. These can be grouped into not fewer than 78 kinds, considered species in disjunct element taxonomy. At least 10 multielement genera and 40 multielement species are represented. Six new species: Diplognathodus illinoisensis, Neognathodus metanodosus, N. polynodosus, N. oligonodsus, N. anodus, and Gondolella pulchra are described. Although all marine beds were formed in shallow water, generally near shore, they represent the products of highly diverse environments. Conodont biofacies are sharply differentiated and mirror this diversity. Ecologic controls that effected conodont distribution are believed to have been salinity, energy, pH, and possibly biologic antagonism. Neognathodus is the most useful conodont genus for biostratigraphy in these rocks. Four zones and subzones are based on species of this genus and it has permitted relatively precise interregional correlations. Secondary zonations can be based on other genera that supplement the Neognathodus zonation and assist in identifying units. In decreasing importance these are Gondolella, the Idiognathodus-Streptognathodus plexus, and Diplognathodus.”