SPATIAL TRENDS IN CONODONT DISTRIBUTION PATTERNS AND TAPHONOMY IN KEY STRATIGRAPHIC SURFACES AND HORIZONS THAT DELINEATE GENETIC UNITS WITHIN THE IOLA LIMESTONE: UPPER PENNSYLVANIAN OF KANSAS AND IOWA

Temporal trends in the distribution of conodonts and facies stacking patterns have long been used to illustrate the transgressive and regressive nature of Upper Pennsylvanian strata that comprise a Kansas Cyclothem. Sequence stratigraphic studies of these rocks have demonstrated complexities not recognized in the cyclothem model, especially by examining spatial trends revealed by correlation of key stratigraphic surfaces. This investigation examines the temporal and spatial trends in the taphonomy and distribution of conodonts within a sequence stratigraphic framework interpreted for sections of the Iola Limestone (Upper Pennsylvanian) of eastern Kansas and central Iowa. Three additional sections have been sampled in eastern Kansas, and results will be compared with three previously sampled sections.

Temporal trends in conodont distribution were examined in samples from correlative sections of the Iola sequence in Kansas and Iowa. An increase in conodont elements/kg characterize the interval directly above all bounding surface types within the Iola. Conodont elements/kg values are much higher, however, in the intervals above the maximum flooding surface or horizon and directly above the sequence boundary, than parasequence boundaries. Generic diversity tends to increase above flooding surfaces, but drop abruptly above sequence boundaries. A change in taxonomic composition of samples above bounding surfaces also distinguishes sequence boundaries and maximum flooding surfaces or horizons from parasequence boundaries.

Spatial trends in conodont distribution and taphonomy were examined in samples above flooding surfaces and unconformities in the Iola. Multivariate statistical analyses of conodont distribution suggest a correlation between sample composition and the relative location of the surface within the basin (updip versus downdip). Spatial trends in taphonomy, particularly fragmentation and bias towards robust elements, help to characterize compound stratigraphic surfaces in updip areas within the basin. Trends in the distribution and taphonomy of conodonts can be used as a tool to assist bounding surface identification (distinguishing between flooding surfaces and sequence boundaries) and to aid in characterization of basinal trends of key surfaces and horizons within marine Paleozoic sequences.