| Over Phanerozoic time scales, stratigraphic records from the cratonic interior are dramatically thinner and generally assumed to be relatively incomplete, with more numerous and longer-duration hiatuses, compared to records from the continental margin. However, this assumption need not be true for the shorter time scales over which accumulation of the preserved stratigraphic record on the craton actually takes place. Based on original, field-collected data, this study compares the stratigraphy and taphonomy of carbonate-dominated sedimentary records from the cratonic interior versus the continental margin. Specifically, I compare the Middle-Upper Devonian of Nevada (continental margin) and Iowa (cratonic interior) to evaluate whether the cratonic record is (1) miniaturized, i.e. thinner, but equally complete; (2) comparable in thickness and quality where the sedimentary record is preserved, but certain portions of the record are notably absent, i.e. omitted or truncated; or (3) so invariably preserved that the stratigraphic packages and skeletal concentrations are qualitatively different compared to the contemporaneous continental margin record.;First, this study finds that where preserved, comparable but thinner facies and meter-scale cycles can be recognized in Iowa. Nonetheless, stratigraphic omission of meter-scale cycles, and to a less extent, facies, does occur. However, the absence of depositional record in Iowa relative to Nevada is likely due to suppression of the subtidal carbonate factory, rather than more frequent subaerial exposure. Next, differences in the taphonomic characteristics of skeletal concentrations between Nevada and Iowa are consistent with lower sedimentation rates in Iowa favoring a greater frequency of taphonomically complex, and potentially more time-averaged assemblages. However, minimal evidence for greater than within-habitat time-averaging suggests that low bioclast input rates, due to low production and/or high pre-burial destruction rates, precluded the accumulation of skeletal concentrations over longer time scales. Finally, the lack of densely packed, laterally extensive, and highly time-averaged shell beds associated with major non-depositional hiatuses (where low bioclast dilution would favor their formation) in both Nevada and Iowa is also consistent with inherently low bioclast input rates in these Devonian carbonates. Taken together, the findings from this study provide new insights into the controls on the quality and preservation of cratonic interior versus continental margin records. |
