A quantitative paleoecological approach to high‐resolution cyclic and event stratigraphy: the Upper Ordovician Miamitown Shale in the type Cincinnatian

Abstract

Stratigraphic cycles form an underlying high‐resolution chronostratigraphic structure for much of the sedimentary record. However, before their chronostratigraphic utility can be realized they must be reliably correlated. A new integrated cyclic, quantitative lithologic and faunal method of correlating meter‐scale cycles has been developed for a 12 m interval of the Miami‐town Shale in the Upper Ordovician of the Cincinnati, Ohio area. First, using lithologic criteria alone, six flooding‐surface‐bound (shale‐on‐limestone) shoaling‐upward (shale‐to‐limestone) cycles were delineated and correlated between seven outcrop sections within a 30 km radius; many correlations were ambiguous. Unusual fossil occurrences constrain correlations of cycles 3 and 4, and the limited presence of a dalmanellid, Heterorthina fairmountensis, shows that the flooding surface above cycle 3 lies 10 cm below the lithologic limestone‐shale contact. Cluster analysis of faunal abundance data constrained correlations between all cycles and showed a major transition at the top of cycle 2, again below the lithologic limestone‐shale contact. Finally, faunal depth gradient fluctuations interpreted from ordination of faunal abundance data confirmed and clarified the nature of cycle correlations; the major transition at the top of cycle 2 is a transgressive surface, and the middle part of cycle 3 includes the interval of maximum water depth. These features delineate a larger, 10‐m‐scale, cyclicity. The smaller, meter‐scale cycles, interpreted as averaging 40–100 ka in duration, demonstrate the potential of a ten‐to twenty‐fold increase in the resolution of the type Cincinnatian stratigraphic record.Ecostratigraphy, faunal cyclicity, cyclic stratigraphy, event stratigraphy epiboles, benthic paleoecology, Upper Ordovician, Maysvillian, Caradocian, Ashgillian, Cincinnati.

The Effects of Spatial Patchiness on the Stratigraphic Signal of Biotic Composition (Type Cincinnatian Series; Upper Ordovician)

“…Even the finer-scale faunal trends from bin to bin exhibit some similarities. These results correspond well with a similar analysis conducted by Dattilo (1996), who used DCA and the ratio of limestone to mudstone to correlate meter-scale cycles for the Miamitown Shale, a unit in the Cincinnatian that lies above the Fairview Formation. Separately comparing trends from each sublocality to K445 again exemplifies the effect of patchiness on the fine-scale signal of biological patterns.…”

“…Fine-scale correlation in the Cincinnatian historically has been problematic (see Dattilo, 1996;Brett and Algeo, 2001c;Miller et al, 2001;Webber, 2004). However, the fifty meter-scale cycles identified by Holland et al (1997) and correlated across a portion of the Cincinnatian region by Brett and Algeo (2001b) provide the necessary criteria for assessing fine-scale regional variation in biotic composition.…”

“…1). As in similar applications of gradient analysis to the fossil record (e.g., Patzkowsky, 1995;Dattilo, 1996), fossil distribution in the lower Cincinnatian correlates with environmental factors related to water depth Miller et al, 2001).…”

“…Gradient analysis is a way to compare quantitatively the composition and abundance of taxa among localities, and, in the marine subfossil and fossil record, is a valuable tool for characterizing the spatio-temporal distribution of organisms according to paleoenvironmental variables (e.g., Cisne and Rabe, 1978;Rabe and Cisne, 1980;Cisne et al, 1982;Springer and Bambach, 1985;Anstey et al, 1987;Miller, 1988;Anstey and Rabbio, 1990;Miller et al, 1992;Lafferty et al, 1994;Patzkowsky, 1995;Dattilo, 1996). A method of high-resolution faunal gradient analysis applied by Holland et al (2001) and Miller et al (2001) and modified by Webber (2002Webber ( , 2004 has provided a valuable means of characterizing the signal of biological variation for strata in the Kope and lower Fairview formations of the type Cincinnatian Series (Upper Ordovician) at a regional scale (Fig.…”

Eustatic and tectonic control on the distribution of marine seismites: examples from the Upper Ordovician of Kentucky, USA

“…Results of new correlations in the RocklandianMaysvillian strata throughout the Kentucky region (Tobin, 1982;Holland, 1993;Holland et al, 1997;Jennette and Pryor, 1993;Dattilo, 1996;McLaughlin and Brett, 2000;McLaughlin et al, in press;Brett and Algeo, 2001;Brett et al, 2000 provide strong evidence for the persistence of certain distinctive decameter-to meter-scale limestone beds and bed bundles or cycles (see Fig. 13A,B).…”