Architecture, process, and environmental diversity in a late cretaceous slope channel system

Benjamin Kneller, Guilherme Bozetti, Richard Callow, Mason Dykstra, Larissa Hansen, Ian Kane, Pan Li, Adam McArthur, Amanda Santa Catharina, Thisiane Dos Santos, Philip Thompson

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


Arroyo San Fernando, on the Pacific coast of Baja California, Mexico, provides a superb view of the architecture of a Maastrichtian active margin slope channel system and the record of its evolution through a third-order sea-level cycle. The succession is organized into architectural building blocks (channel-complex sets) consisting of a channel belt with an axial region and a channel-belt margin of terraces and internal levees. The channel belt is confined by an external levee on one side and by an erosion surface into the slope on the other. Each channel-complex set can be subdivided into three stages of evolution: Stage I consists of highly amalgamated coarse-grained channel complexes, Stage II consists of gravelly meander belts with marginal and stratigraphically intervening thin-bedded turbidites, and Stage III consists of mudstones representing abandonment. This succession is associated with repeated and therefore predictable changes in architecture, facies distribution, inferred seafloor morphology, and sedimentary process. We describe variability in the sedimentology, ichnology, palynology, provenance, and inferred sedimentary processes between and within these architectural elements. Channel formation and fill are attributed to erosion, sediment transport, and deposition by turbidity currents and lesser debris flows. Ichnology indicates enhanced oxygenation and supply of organic material, substrate type, and turbidity within the channel belt; the axial region can be differentiated from the terraces by differing response to turbidity-current intensity. Levee environments show ichnological gradients away from the channel towards background slope. Palynology reflects confinement of the supply of terrigenous material to the channel belt, but is also indicative of stratification within the turbidity-currents, as is the distribution of heavy minerals. Provenance is from the extinct part of the continental-margin arc to the east, via high-gradient gravelly streams and across a steep shoreline, with direct supply of coastal material to deep water. Architectural hierarchy bears comparison with other slope channel systems, but in common with them the fill represents only a small fraction of the time that the system was active.

Original languageEnglish
Pages (from-to)1-26
Number of pages26
JournalJournal of Sedimentary Research
Issue number1
Publication statusPublished - 14 Jan 2020

Bibliographical note

Funding Information:
Our thanks to Kirt Campion, Tim McHargue, and Associate Editor Morgan Sullivan for particularly helpful and constructive reviews. We gratefully acknowledge Luke Fairweather, Alex Fordham, Fabiano Gamberi, Mark McKinnon, Zonia Palacios, Daisy Pataki, Dylan Rood, Sacha Tremblay, Natasha Tuitt, Cristian Vallejo, Hongjie Zhang, and especially Juan Pablo Milana, all of whom helped with the mapping, description, and interpretation. Thanks to Claus Fallgatter for help with the drafting of Figure 13, and to John Southard for thorough editing. BK and MD sincerely thank Cathy Busby and Bill Morris for introducing us to this system.

Publisher Copyright:
Copyright © 2020, SEPM (Society for Sedimentary Geology)


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