Fluvial stratigraphic architecture of the John Henry member of the Straight Cliffs Formation, Kaiparowits Plateau, Utah, USA.

摘要

Understanding how changes in fluvial and marginal marine architecture correlate with shifts in marine shoreface architecture is a crucial step to understanding the effect of relative sea level changes on terrestrial sedimentary systems. Outcrop and subcrop data from the John Henry Member of the Straight Cliffs Formation illustrate regional nonmarine-marine stratigraphic correlations and address sequence stratigraphic models based on such correlations. Three measured sections and two logged cores (each >230 m), 2367 paleocurrent measurements, and examinations of lateral facies relationships were made in the John Henry Member. Three facies associations identified in fluvial and paralic sections correlate to downdip marine and shoreline equivalents as follows: Facies association 1 (FA-1, the lowermost interval) consists of tidally influenced, laterally restricted fluvial channel belts, coastal mire, and shoreface sandstone. FA-1 correlates to a lower marine package that shows net progradation and consists of vertically thick, laterally extensive regressive shoreface sandstones intercalated with transgressive lagoonal deposits. Facies association 2 (FA-2, the middle interval) consists of laterally restricted, highly sinuous fluvial channel belts, lagoonal and estuarine coastal plain mires, bay-head deltas, isolated distributary channels and tidal channels. FA-2 correlates downdip with a middle marine package that shows net transgression and consists of vertically thin, laterally restricted regressive shoreface deposits intercalated with thick transgressive lagoonal deposits and barrier island sandstone. Facies association 3 (FA-3) consists of laterally extensive, low sinuosity fluvial channel belts and vertically amalgamated fluvial channel belt complexes, and floodplain overbank. The marine equivalent of FA-3 shows net progradation and consists of vertically thick, laterally extensive regressive shoreface sandstones intercalated with transgressive lagoonal deposits.;Preserved within each marine package are multiple transgressive-regressive cycles, but the fluvial architecture does not appear to respond to this scale of cyclicity. The observed evolution of fluvial systems and the inferred relationship to relative sea level change is distinct from previous interpretations of these strata. Autogenic or allogenic trunk channel avulsion may exert a primary control on the overall relationships between marine, paralic and fluvial stratigraphy in the John Henry Member.