High Fidelity? Temporal and spatial scales of stratigraphic incompleteness and how they compare to environmental forcings

Abstract:

Stratigraphy contains the most complete record of information necessary to quantitatively reconstruct paleolandscape dynamics, but this record contains significant gaps over a range of time and space scales. These gaps result from stasis on geomorphic surfaces and from erosional events. We examine stratigraphic completeness in a suite of 11 physical experiments where the topography of aggrading deltas was monitored at high temporal and spatial scales. These experiments cover a range of boundary conditions, with both constant and dynamic forcings. Our analysis centers on three time scales: (1) the time at which a record is discretized (t), (2) the time necessary to build a deposit with mean thickness equivalent to the maximum topographic roughness (Tc), and (3) the time necessary for channelized flow to migrate over the entire basin (Tch). These time scales incorporate information pertaining to the evolving topography of actively changing surfaces, kinematics by which the surfaces are changing, and net deposition rate. In constant boundary condition experiments, we find that stratigraphic completeness increases as a power law function of t/Tc until reaching 100% completeness at time scales equal to Tc. The relationship between completeness and t/Tc in experiments experiencing base-level cycles is complex and related to characteristics of the base level cycles. We observe that in our experiments the mean and standard deviation of the width of stratigraphic gaps scales with Tc/Tch. These results place quantitative limits on the fidelity of the stratigraphic record, and thus aid prediction of a depositional environment’s capacity to store environmental signals.