Stratigraphy -- The Fall of Continuity

The twentieth-century theme of discontinuity has begun to invade stratigraphy. It is implicit in the recently-developed sea-level curve and in the realization that fracture rather than simple flexure controls basin development. The recognition of discontinuity in the stratigraphic record is changing our views of two of Steno's principles, Superposition and Original Lateral Continuity. Small-scale vertical discontinuity is exemplified by bedform migration, storm deposition, turbidite sedimentation, fan or delta-lobe switching, channel or inlet migration. On a larger scale, transgressive overstep marked by a subtle disconformity is a common feature in the record. Its recognition has led to a new model for cyclothem deposition, in which the cycles are strongly asymmetric and regressive dominant. Similar cycles have been advocated for carbonate sequences. Transgressive disconformities are important to identify, because their presence invalidates the use of Walther's Law. Vertical discontinuity on a grand scal...