Video
Abstract
The stratigraphic record is famously incomplete. The Sadler effect implies that there are gaps all the way down, and numerical experiments suggest that environmental signals are more often shredded or buffered than preserved. This talk argues that, within this sea of incompleteness, there are islands of surprisingly complete, high-frequency record — and that they are worth looking for. Three examples make the case. (1) The laminated siltstones of the Permian Spraberry Formation in the Midland Basin can be correlated lamina by lamina between cores that are up to 15 kilometers apart. Such continuity rules out deposition by bottom-hugging currents and suggests instead that each lamina records the settling of wind-blown silt from a single storm. (2) The cyclic cross strata of the Jurassic Navajo Sandstone in southern Utah record seasonal reversals of a bidirectional wind regime. Orthophoto panels of two outcrops, topological sorting of mapped facies polygons into stratigraphic successions, and cellular-automaton dune modeling all point to grain flows and ‘wedge’ deposits that alternate on an annual cycle, with a modern analog at White Sands. (3) Point bars of rapidly migrating meandering rivers such as the Rio Mamoré and the Purus grow at smooth, characteristic rates; most of them are cannibalized, but those that survive are, in effect, stacks of flood deposits. The common thread is ‘strange ordinariness’: preservation of any given event is rare, but what does get preserved is ordinary. At short timescales, where the coupling between forcing and response is direct, signals need not be shredded — and basic architectural elements such as a point bar, a cross set, or a piece of laminated core should plot as straight-line segments on a Sadler diagram rather than as part of the fractal cloud. At sub-Milankovitch resolution, seasonality emerges as the dominant pacemaker of Earth surface processes, and hence of the sedimentary record.
Event
Geological Society of America Sedimentary Geology Division Lecture Series (inaugural lecture), July 2, 2026.