Rock outcrops of the sedimentary-stratigraphic record often reveal bedding planes that can be considered to be true substrates: preserved surfaces that demonstrably existed at the sediment–water or sediment–air interface at the time of deposition. These surfaces have high value as repositories of palaeoenvironmental information, revealing fossilized snapshots of microscale topography from deep time. This talk will discuss ideas about how such true substrates are preserved, what they can inform us about ancient environments and stratigraphic time at outcrop, and why they seem to be so counterintuitvely abundant in the sedimentary record.