The Lower Ordovician mixed carbonate–shale Dumugol Formation of Korea was analysed to compare the stratal thickness and facies proportion of measured and decompacted successions and to assess the effect of compaction on the interpretation of cyclicity. Metre-scale cyclic units (MSUs) in the formation consist in part of outer-shelf shale, distal to intermediate mid-ramp limestone–shale couplets, and proximal mid-ramp lime mudstone facies. A total of 119 MSUs were recognised in the studied section. Thickness reduction was estimated based on petrographic evidence, including compressed to uncompressed burrows, firm- to hardground surfaces and differentially compacted laminae, and supplementary values of decompaction factors taken from the literature. Five oscillatory units in the apparent Fischer plots consist of thickening- to thinning-upward packages composed of shallowing- to deepening-upward MSUs. Similar thickness–facies relationships were observed in the lower two oscillatory units of the decompacted Fischer plots; these units are rich in shale. In contrast, a transition to an antithetic thickness–facies pattern occurs in the upper interval of the second oscillatory unit and persists in the following units, with common occurrences of limestone facies. The different thickness–facies relationships in the measured and decompacted Dumugol successions indicate that a large portion of the major controls on the formation of sedimentary cyclicity changed from sediment accumulation rate to relative sea-level fluctuations. Such modification by compaction of the original sediment column appears to have been caused by early cementation in calcareous sediments, which resulted in differential thinning between limestone and shaly deposits. These findings reveal that diagenetic influences on sequence-stratigraphic and cyclostratigraphic interpretations have been underestimated, with consequent potential effects on associated local to regional geodynamic models, particularly for mixed carbonate–siliciclastic successions.

对韩国的下奥陶纪碳酸盐岩-页岩Dumugol混合岩层进行了分析，以比较测得和压实的演替的地层厚度和相比例，并评估压实作用对周期性的解释。地层中的米级循环单元（MSU）包括部分外页岩，中斜坡上的中灰岩-页岩对联的远端到中斜坡石灰岩的近端相。在研究的部分中，总共认可了119个MSU。厚度减少是根据岩石学证据估算的，包括压缩到未压缩的洞穴，硬地表层到硬地表层以及压实的薄片，以及从文献中获得的解压因子的补充值。明显的菲舍尔图中的五个振荡单位由增厚到变薄向上的包裹组成，而变薄的是由浅到深的向上的MSU组成。在解压缩的Fischer图的下部两个振荡单元中观察到了相似的厚度-相关系。这些单位富含页岩。相比之下，在第二个振荡单元的上部区间中发生了向对立的厚度相模式的转变，并在随后的单元中持续存在，并经常出现石灰岩相。在测得的和解压缩的杜姆古勒演替中，不同的厚度相关系表明，对沉积循环形成的主要控制的很大一部分从沉积物积累速率变为相对海平面波动。通过压实原始沉积物柱而进行的这种修改似乎是由于钙质沉积物中的早期胶结作用引起的，这导致了石灰岩和泥质沉积物之间的差异性变薄。这些发现表明，成岩作用对层序地层学和旋回地层学解释的影响被低估了，从而对相关的局部到区域地球动力学模型，特别是碳酸盐-硅质碎屑混合演替的潜在影响。