C. Drummond et H. Sheets, Taphonomic reworking and stratal organization of tempestite deposition: Ordovician Kope Formation, northern Kentucky, USA, J SED RES, 71(4), 2001, pp. 621-627
Tempestite beds of the Ordovician Kope Formation of northern Kentucky provi
de an interesting subject for numerical simulation and stratigraphic analys
is, Taphonomic characteristics of these shell-rich beds suggest that they w
ere formed by multiple reworking and amalgamation events. If so, then storm
-driven redepositional processes could have led to temporal condensation wi
thin the tempestite beds. Numerical simulation of tempestite formation indi
cates that storm-bed abundance is maximized by frequent, weak storm events,
whereas shell degradation is increased by frequent, strong storms. Convers
ely, these stratigraphic and taphonomic parameters are insensitive to chang
es in storm intensity when such events are relatively uncommon. Additionall
y, the stratigraphic and taphonomic characteristics of tempestite formation
are found to be largely insensitive to the abundance of shell material in
the undisturbed shale,
Lacunarity analysis of the vertical spacing of Kope Formation tempestite be
ds (grainstones and packstones) demonstrates stratal clustering. Such clust
ering was caused by either absolute or relative changes in storm intensity
or frequency. Given the temporal scale of tempestite clustering within the
Kope, changes in water depth across the shallow shelf-driven either by chan
ges in sea level or sedimentation rate-is a likely mechanism by which such
relative changes in storm processes occurred. Conversely, climatologic vari
ability at the scale of tens to hundreds of thousands of years could drive
absolute changes in storm intensity leading to stratigraphic clustering of
tempestite beds.