The Cretaceous Cliff House Sandstone comprises a thick (400 m) net-
transgressive succession representing a mixed wave- and tide-influenced shallow-marine
system that migrated episodically landwards. This study examines the youngest part
(middle Campanian) of the Cliff House Sandstone, exposed in Chaco Cultural Natural
Historical Park, northwest New Mexico, U.S.
A. Detailed mapping of facies architecture
between a three-dimensional network of measured sections has allowed the character,
geometry, and distribution of key stratigraphic surfaces and stratal units to be
reconstructed. Upward-shallowing facies successions (parasequences) are separated by
laterally extensive transgressive erosion (ravinement) surfaces cut by both wave and tide
processes. Preservation of facies tracts in each parasequence is controlled by the depth of
erosion and migration trajectory of the overlying ravinement surfaces. In most
parasequences, there is no preservation of the proximal wave-dominated facies tracts
(foreshore, upper-shoreface), resulting in thin (4–7 m) top-truncated packages. Four
distinct shallow marine tongues (parasequence sets) have been identified, consisting of
ten parasequences with a total stratigraphic thickness of ~ 100 m. Each tongue records an
episode of complex shoreline migration history (multiple regressive–transgressive
phases) in an overall net-transgressive system.
The ravinement surfaces provide a stratigraphic framework in which to understand
partitioning of tide- and wave-dominated deposits in a net-transgressive system, and a
model is presented to account for the sediment distribution and stratigraphic architecture
observed in each parasequence. Despite a complex internal architecture, parasequences
exhibit a predictable pattern which can be related to the regressive and transgressive
phases of deposition. Preservation of wave-dominated facies tracts is associated with
shoreline regression, while tide-dominated facies tracts are interpreted to record sediment
accumulation during shoreline transgression that also resulted in significant erosion of
the underlying regressive deposits. The interplay between erosion, sediment bypass, and
deposition during regression and transgression is shown to ultimately control the
preservation and stratigraphic architecture of the larger-scale net-transgressive coastal
system. While the Cliff House Sandstone exhibits a facies composition and quantitative
stacking patterns (shoreline trajectory) similar to other studied examples, differences in
the dip-extent of the wave-dominated sandstone tongue has resulted in a more disconnected architecture between the high-fr
equency cycles. Understanding the variety
of stratal geometries that ravinement surfaces can generate is therefore crucial to
predicting the spatial distribution and facies architecture in transgressive systems.