Ichnology, sedimentology and stratigraphy of the Lower Cretaceous Viking Formation at Mikwan, Fenn and Chain, Alberta, Canada.

摘要

Siliciclastic facies from the Lower Cretaceous (Albian) Viking Formation in Townships 32-38, Ranges 16-24W4 were studied in detail. Ichnology is integrated with physical sedimentology and stratigraphy in order to resolve the depositional history of the Viking Fm in the study area.;The Viking Fm in the study are can be differentiated into 13 facies, which are arranged into five recurring facies associations. The lowermost facies association (FA1) consists of a progradational parasequence set of the Highstand System Tract and is representative of Regional Viking deposits. A relative sea level fall, followed by transgressive ravinement, generated Discontinuity 3, which incised into FA1, and is interpreted to be an almagamated flooding surface/sequence boundary (FS/SB). Fully marine shoreface deposits comprising FA2 overlie Discontinuity 3 and constitute an incised shoreface complex deposited during a stillstand in transgression. A fall in relative sea level, followed by transgression, led to the incision of Discontinuity 2 into FA2. FA3 is dominated by coarse-grained, trough cross-bedded sandstones containing mudstone interbeds, mudstone interlaminae and mudstone rip-up clasts interstratified with interbedded mudstones and sandstones. Resumption of transgression led to the development of a ravinement surface designated Discontinuity 1 which rises landward in a "step-wise" fashion. Fully marine, offshore deposits of FA4 overlie Discontinuity 1. A regional fall in relative sea level followed by incremental transgression led to formation of the regionally extensive VE4 surface. VE4 is overlain by conglomerates and sandstones of FA5. (Abstract shortened by UMI.).