Autogenic Sedimentation in Clastic Stratigraphy

Abstract

Internally generated, or autogenic, terrestrial and marine sediment-transport dynamics can produce depositional patterns similar to those associated with climatic, tectonic, or sea level changes. A central challenge in accurately interpreting the sedimentary archive is determining what scales and types of deposits reflect autogenic controls on sedimentation in different environments. Autogenic sediment-transport dynamics commonly result from intermittent sediment storage in transient landforms, which produces episodic, spatially discontinuous sedimentation across a basin. The transition from localized, variable sedimentation to even, basin-wide sedimentation marks the shift from stochastic landscape dynamics to deterministic deposition responding to the long-term balance between sediment supply and the creation of space to accommodate sediment. This threshold can be measured in a wide variety of stratigraphic successions and has important bearing on whether climatic, tectonic, or sea level signals can be recognized in physical sedimentary deposits.

Buffered, Incomplete, and Shredded: The Challenges of Reading an Imperfect Stratigraphic Record

“…Stochastic dynamics in SRSs arise for two reasons: environmental stochasticity and autogenics. Environmental stochasticity refers to events like earthquakes, storms, and floods which are difficult to predict given their chaotic response to initial conditions but can impart significant variability to sediment flux and accommodation for sediment storage (Ashton et al, ; Goldfinger et al, ; Hajek & Straub, ; Peters & Loss, ). For example, landscape thresholds mean that some depositional environments, or parts of depositional environments, are only activated during events of a given magnitude.…”

“…The stratigraphic recording process is further complicated by patterns and dynamics in SRSs that arise solely as a consequence of the interaction of the components within a system (Greenberg, ; Hajek & Straub, ; Muto et al, ; Paola, ). These autogenic (Table ) dynamics are often discussed in comparison to allogenic processes (i.e., environmental forcings).…”

“…The representation of landscapes as diffusive does not explicitly incorporate the specific processes and landscape dynamics that give rise to the diffusion of sediment through SRSs (Hajek & Straub, ; Hajek & Wolinsky, ; Malmon et al, ; Métivier, ; Paola, ; Parker, ; Phillips & Jerolmack, ; Simpson & Castelltort, ). Therefore, diffusional representations of SRSs over mesotime scales implicitly assume (an unspecified degree of) spatiotemporal averaging in response to an environmental signal.…”

“…In channelized systems, paleoflow‐depth measurements (e.g., from scour surfaces or preserved bar‐clinoform heights) are a sensible starting point for estimating l and reconstructing a minimum estimate of T c . To explore upper‐limit estimates of T c , however, maximum estimates of channel belt sand body thickness or even the thickness of stacked channel belt clusters should be used to account for the potential influence of mounding from alluvial ridge or fluvial fan deposition (Hajek & Straub, ). Characterizing T c also necessitates an estimate of long‐term aggradation rates, r .…”

A Stratigraphic Framework for the Preservation and Shredding of Environmental Signals

“…Stratigraphic patterns linked to changes in this volumetric balance operate at time scales >10 6 years (Armitage et al, ; Duller et al, ; Paola et al, ). At time scales <10 6 years it is often difficult, but sometimes possible (Blum et al, ), to distinguish allogenic stratigraphic structure from structure generated by processes internal to a sediment routing system, which occur over similar time scales (i.e., autogenic processes; Li et al, ; Hajek & Straub, ).…”