Time, space and synoptic topography: how to read outcrops as a granular record of Earth history

Siliciclastic strata commonly preserve chronostratigraphic surfaces that record the ancient interface of sediment and water/air, in the form of true substrates on bedding planes and sampled topography in stratigraphic profiles. Such surfaces are commonly a reflection of sedimentary stasis, a sedimentation state where neither deposition or erosion was occurring. Sedimentary stasis may be instantaneous, temporary or prolonged, and may also be considered to occur when the constituent grains of a substrate remain in motion as the surface active layer, when the elevation of the lithic surface does not change. The preservation of patches of synoptic topography requires only that sedimentation states of deposition, erosion and stasis fluctuate, but is more common in lower energy parts of a depositional environment. Certain sedimentary features associated with true substrates and sampled topography can, through modern analogy, be used to determine the likely duration of sedimentary stasis. Here we use original case studies to show how the duration of this stasis can be variable depending on facies and stratal age, but that at outcrop scale it is always a very short interval relative to the longevity of a depositional environment. With examples from several siliciclastic facies and geological periods, we show that stratigraphic time preserved at outcrop scale can be very short, indicating that the total stratigraphic record is built brick-by-brick from many lower hierarchy snapshots. This understanding shifts perspectives on the stratigraphic record as an archive, with implications for the meaning of sedimentary signatures at outcrop and the construction of narratives to understand Earth history.