Abstract:
This chapter discusses the recognition of the soft-sediment deformations as early-diagenetic features. The early-diagenetic stage— that is, the period between sedimentation and lithification, includes some important changes within most types of sediments. The most obvious is the common reduction of thickness by compaction, a process that includes reduction of pore size, particularly, in fine grained sediments, and most commonly, expulsion of pore water. The fact that geology could develop as a science of crucial importance to mankind is due to careful analyses of rock features and subsequent derivation of “geological laws.” One of the first principles recognized was the law of superposition: layers gradually become younger in an upward direction, at least, if the succession is undisturbed. Layering of sedimentary rocks has long been the clue for unraveling the stratigraphy of rocks. It can thus be understood that, in addition to the layer-intersecting dikes, other types of irregular layering also attracted attention. This is reflected by the interest in structures, such as convolutions and slumps. The “normal” inventory of early-diagenetic deformations, made in order to unravel the history of the sediment before lithification, has resulted in an overwhelming number of descriptions and analyses, sometimes only as “by-products,” sometimes as primary research topics.