6 Surficial geology and neotectonics in the West: Celebrating and advancing the legacy of Kirk Bryan through field-based geomorphology studies (Posters)

This session invites and examines recent field-based geomorphology studies in the West. Contributions regarding soils geomorphology, neotectonics, pediments, fluvial terraces, and landscape development are invited.

Monday, 18 May 2026
8:00 AM - 5:30 PM
Alvarado D/E

Kaibab-surface drainages in eastern Grand Canyon: Insights into canyon formation processes

Paper number: 6-3
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

In the eastern Grand Canyon, Permian Kaibab-Formation-surface (K-s) drainages on the Kaibab and Coconino Plateaus are interpreted to have co-evolved with the paleo-Colorado River. Mapping in the region reveals two superimposed drainage patterns. The first drainage pattern is consequent on the resistant K-s plateaus, with hundreds of down-dip channels radiating outward from the crest of the Kaibab Upwarp.  The second (initially-subsequent) drainage pattern is that of the Colorado River, which was positioned on the southern slope of the Kaibab Upwarp and flowed parallel to bedding strike and 90° to the K-s drainages.

Both north-rim and south-rim K-s drainages, as well as some relict K-s drainages stranded on top of inner-canyon buttes, are now truncated by the walls of the modern Grand Canyon. The north and south rim K-s drainages show no evidence of having been formerly connected.  

These drainage patterns, combined with regional relationships indicate the following sequence:

-       Laramide folding and uplift of the Kaibab Upwarp.

-       Erosion of Mesozoic strata, first from the high points in the upwarp in the north rim area, with southward, eastward and westward retreat of arcing, strike-parallel, cuestas and strike valleys.

-       Development of a prominent strike valley above the site of the modern Colorado River, and incision of this strike valley into the Kaibab Formation to form a “proto-Grand Canyon” (flow directions unknown). At this time, on the Kaibab Plateau a radiating “dip-parallel” K-s drainage network developed, while south side drainages flowed north (obsequent) on non-dip-plane areas with retreating, Mesozoic-hosted cuestas.

-       The proto-Grand Canon deepens and widens (likely no deeper than the Redwall Limestone).

-       On the south rim, as Mesozoic strata retreat to the south, K-s drainages form in a radial pattern, flowing away from the axis of the Kaibab Upwarp.

-       At Red Butte, near the south rim, a basalt flow caps the Triassic Shinarump member of the Chinle Formation at 9.17 Ma. 

-       South rim K-s drainages are incised into the underlying Kaibab Formation as Triassic strata continues its southward retreat.

-       After integration of the western Grand Canyon and lower Colorado River, at approximately 5.5 Ma, extreme deepening and widening of the Grand Canyon begins resulting in numerous truncations of north rim, south rim and inner-canyon butte K-s drainages, exposed today.

Geological Society of America Abstracts with Programs. Vol. 58, No. 4

doi: 10.1130/abs/2026RM-410544

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